WIND ANALYSIS AND ESTIMATE OF THE WIND SHEAR EXPONENT OF THE SULAYMANYIAH INTERNATIONAL AIRPORT AREA
A thesis Submitted to the Council of Faculty of Science and Science Education School of Science at the University of Sulaimani In partial Fulfillment of the Requirements for the Degree of Master of Science in Physics
By Aso Othman Abdulla B.Sc. Physics (2008), Salahaddin University - Erbil
Supervised by Dr. Salahaddin Abdul-Qader Ahmed Assistant Professor
Pûşper / 2714
June / 2014 i
Supervisor Certification
I certify that the preparation of thesis entitled "WIND ANALYSIS AND ESTIMATE OF THE WIND SHEAR EXPONENT OF THE SULAYMANYIAH INTERNATIONAL AIRPORT AREA" accomplished by Aso Othman Abdulla was prepared under my supervision in the School of Science, Faculty of Science and Science Education at the University of Sulaimani, as partial fulfillment of the requirements for the degree of Master of Science in Physics.
Signature: ……………………. Name: Salahaddin Abdul-Qader Ahmed Title: Assistant Professor Date:
/ /2014
In view of the available recommendation, I forward this thesis for debate by the examining committee.
Signature: ……………………… Name: Dana Abdulla Tahir Title: Assistant Professor Date:
/
/2014
ii
Linguistic Evaluation Certification
I hereby certify that this thesis entitled "WIND ANALYSIS AND ESTIMATE OF THE WIND SHEAR EXPONENT OF THE SULAYMANYIAH INTERNATIONAL AIRPORT AREA" prepared by Aso Othman Abdulla, has been read and checked and after indicating all the grammatical and spelling mistakes; the thesis was given again to the candidate to make the adequate corrections. After the second reading, I found that the candidate corrected the indicated mistakes. Therefore, I certify that this thesis is free from mistakes.
Signature: ……………………. Name: Sarah Kamal Othman Position: English Department, School of Languages, University of Sulaimani Date: 28 / 4 / 2014
iii
Examining Committee Certification We certify that we have read this thesis entitled "WIND ANALYSIS AND ESTIMATE OF THE WIND SHEAR EXPONENT OF THE SULAYMANYIAH INTERNATIONAL AIRPORT AREA" prepared by Aso Othman Abdulla, and as Examining Committee, examined the student in its content and in what is connected with it, and in our opinion it meets the basic requirements toward the degree of Master of Science in Physics.
Signature: . . . . . . . . . . . . . . . . . .
Signature: . . . . . . . . . . . . . . .
Name: Dr. Mohammed A. Saeed
Name: Dr. Meeran A. Omer
Title: Assistant Professor
Title: Assistant Professor
(Chairman)
(Member)
Date: 3 / 7 / 2014
Date: 3 / 7 / 2014
Signature: . . . . . . . . . . . . . .
Signature: . . . . . . . . . . . . . . . . . .
Name: Dr. Khalid A. Abbas
Name: Dr. Salahaddin A. Ahmed
Title: Lecturer
Title: Assistant Professor
(Member)
(Member & Supervisor)
Date: 3 / 7 / 2014
Date: 3 / 7 / 2014
Approved by the Dean of the Faculty of Science and Science Education. Signature: . . . . . . . . . . . . . Name: Bakhtiar Qader Aziz Title: professor Date:
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/
/2014
Dedicated to: - My parents, - My wife – Nishtman, and - Kids: Arwand and Barin
v
……………………………………………………………………………………………………....... Acknowledgments
ACKNOWLEDGMENTS First of all, I would like to thank Allah, for the knowledge, the ability and the patience he gave me to carry out this piece of work. I would like also to express my gratitude and appreciation to my supervisor, Assistant Prof. Dr. Salahaddin Abdul-Qader Ahmed for all his support and guidance throughout the whole work of this thesis. I would like also to thank the Sulaymanyiah International Airport director and the manager of meteorological department Mr. Soran for providing me wind data and related information. My thanks are also to my family who has given me support in so many ways during the period of my work. Last, but not the least, I thank all these who helped me both academically and through motivations.
vi
…………………………………………………………………………………………………………………………. Abstract
ABSTRACT
In this study, annual, seasonal and monthly wind characteristics of wind speed variations, standard deviation, wind direction variations, percentage frequency distribution of wind speed and direction and persistence of direction for selected sites 3 and 7, were analysed using wind data time series recorded every one minute for the period of one year 2012 at 15 m height at Sulaymanyiah International Airport area, located in the west of Sulaymanyiah city, in the northeast of Iraq. Based on these data, it was found that for both sites 3 and 7 the minimum and maximum monthly mean wind speed were in January and June respectively, while the minimum and maximum seasonal mean wind speed in winter and summer respectively. For both sites 3 and 7 the annual and most seasons have maximum percentage frequencies of wind speed (≥4.5m/sec). Also it was found that for both sites 3 and 7 the monthly and seasonal resultants wind direction had maximum persistence in August and summer season. Using Lakes Environmental Software (WRPLOT View) for wind direction analysis, it was found that for both sites 3 and 7 the seasonal prevailing wind direction at studied area was in westnorthwest, while the annual prevailing wind directions were between north-northwest and west-northwest for site 3 and west-northwest for site 7. Wind rose analysis showed that for both sites 3 and 7 the resultant vector of wind direction was fairly consistent between 278 and 360 degree which is generally from the west to the north for the annual, seasons and most of the months. Also the values: annual, seasonal, monthly, and diurnal wind shear exponent (α) were estimated using two different methods based on one-minute wind speed recorded at site 1 (20 m) and site 2 (15 m), then validation was performed on an hourly average basis, using estimated monthly value of α to calculate the monthly vertical wind shear by extrapolating (using power-law equation) the wind speed recorded at 20 meters above ground level to 100 meters and estimated the values of horizontal wind shear intensity.
vii
…………………………………………………………………………………………………………………........... Contents
CONTENTS
Dedication …………………………………………………………………………………………………..
v
Acknowledgments ……………………………………………………………………………………….
vi
Abstract ……………………………………………………………………………………………………….
vii
Contents ………………………………………………………………………………………………………
viii
List of Tables ………………………………………………………………………………………………
x
List of Figures ………………………………………………………………………………………………
xii
List of Symbols …………………………………………………………………………………………….
xiv
CHAPTER ONE: INTRODUCTION ………………………………………………………………..
1
1.1
Wind ……………………………………………………………………………………..
1
1.2
Origin and Fundamental Causes of Wind ……………………………..
2
1.3
Meteorology of Wind Direction and Speed …………………………..
3
1.4
Wind Shear …………………………………………………………………………..
4
1.5
Literature Review …………………………………………………………………
5
1.6
Objectives …………………………………………………………………………….
8
CHAPTER TWO: THEORY …………………………………………………………………………..
9
2.1
Atmospheric Boundary Layer …………………………………….…………
9
2.2
Wind Profile ………………………………………………………………………..
10
2.2.1
Wind Profile Log-Law ….............................................................
11
2.2.2
Wind Profile Power Law ……………………………………………………….
13
2.3
Determination of the Wind Shear Exponent ………………………..
13
2.3.1
Justus and Mikhail Method …………………………………………………..
14
2.3.2
The (1/7) Power Law Method ……………………………………………….
14
2.3.3
The Roughness Length Method …………………………………………….
15
2.4
Mean Wind Speed Direction …………………………………………………
16
viii
…………………………………………………………………………………………………………………........... Contents
2.5
Persistence of Direction …………………………………………………......
16
2.6
Topography …………………………………………………………………………
17
2.6.1
Surface Roughness ………………………………………………………………
17
2.6.2
Obstacles ……………………………………………………………………………..
18
2.6.3
Terrain Orography ………………………………………………………………..
18
2.7
Roughness Length ( ) …………………………………………………………
19
CHAPTER THREE: RESULTS AND ANALYSIS ………………………………………………
21
3.1
Introduction ………………………………………………………………………….
21
3.2
Average Wind Speed Analysis ……………………………………………....
22
3.3
Wind Speed Frequency Distribution ………………………………………
25
3.4
Persistence of Direction …………………………………………………………
28
3.5
Wind Direction Analysis ………………………………………………………….
33
3.6
Estimation of Wind Shear Exponent (α) ……………………….………..
50
3.7
Estimation of Wind Shear …………………………………………….………..
56
3.7.1
Vertical Wind Shear ………………………………………………………………
3.7.2
Horizontal Wind Shear …………………………………………………………
57 58
CHAPTER FOUR: CONCLUSIONS AND SUGGESTIONS …………………………………
60
4.1
60
4.2
Conclusions …………………………………………………………………………….. Suggestions for Future Works ………………………………………………….
References ………………………………………………………………………………………………
ix
62
63
………………………………………………………………………………………………………………….. List of Tables
LIST OF TABLES
Table No.
Table Title
Page No.
2-1
Wind shear exponent (α) of various terrains……………………
15
2-2
Roughness classes and the associated roughness lengths
20
3-1
Geographic coordinates and altitude for selected sites...
21
3-2
Eight circular direction sectors system…………………………..
28
3-3
Monthly and annual values of (
,
, , Ө, mean V and
%) for sites 3 and 7 ………………………………………………….. 3-4
Seasonal values of (
,
, R, Ө, mean V and
32
) for
sites 3 and 7…………………………………………………………………….
32
3-5
Twelve circular direction sectors system……………………....
33
3-6
Monthly mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 3 ………………………………………………………………………………
3-7
35
Monthly mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 7 ……………………………………………………………………………..
3-8
36
Seasonal mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 3 ……………………………………………………………………………..
3-9
37
Seasonal mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 7 ……………………………………………………………………………..
3-10
Monthly percentage and direction of the resultant mean wind direction for sites 3 and 7 ………………………………………
3-11
45
Seasonal percentage and direction of the resultant mean wind direction for sites 3 and 7………………………………………..
3-12
37
48
Estimated diurnal wind shear exponent (alpha) value using Eq. (2-6)……………………………………………………………….. x
50
………………………………………………………………………………………………………………….. List of Tables
3-13
Estimated diurnal wind shear exponent (alpha) value using Eq. (2-7)…………………………………………………………………
3-14
51
Estimated monthly values of wind shear exponent (α) and mean wind speeds using Eqs. (2-6 and 2-7) of studied area………………………………………………………………………………….
3-15
54
Estimated seasonal values of wind shear exponent (α) and mean wind speeds using Eqs. (2-6 and 2-7) of studied area…………………………………………………………………………………
3-16
55
Estimated monthly vertical wind shear at (20 to 100) m height using Eq. (2-5) with estimated α by Eqs. (2-6 and 2-7)…………………………………………………………………………………
3-17
58
Estimated monthly horizontal wind shear intensity using mean wind speed of sites (3 and 7)…………………………………
xi
59
………………………………………………………………………………………………………………….. List of Figures
LIST OF FIGURES
Figure No.
Figure Title
1-1
General world wind circulation…………………………………………..
2-1
The troposphere can be divided into two parts: a boundary
Page No. 3
layer (shaded) near the surface and the free atmosphere above it…………………………………………………………………………….
9
2-2
Wind Profiles…………………………………………………………………….
10
2-3
Neutral, stable and unstable of wind profile……………………
12
2-4
Roughness length……………………………………………………………..
17
2-5
Speed up effect…………………………………………………………………
19
3-1
Study Area and Sites Location……………………………………………
22
3-2
Monthly variation of mean wind speeds for selected sites of studied area ……………………………………………………………………….
3-3
23
Seasonal variation of mean wind speeds for selected sites of studied area………………………………………………………………….
24
3-4
Monthly St.Dev. vs Mean wind speed for site 3 and 7…………
24
3-5
Seasonal St.Dev. vs Mean wind speed for site 3 and 7 ……….
25
3-6 a
A percentage histogram for winter …………………………………….
26
3-6 b
A percentage histogram for spring …………………………………….
26
3-6 c
A percentage histogram for summer ………………………………….
27
3-6 d
A percentage histogram for autumn ……………………………….....
27
3-6 e
Annual percentage histogram …………………………………………...
28
3-7
Monthly resultant wind direction for site 3 ……………………….
29
3-8
Monthly resultant wind direction for site 7 ……………………..
30
3-9
Seasonal resultant wind direction for site 3 ……………………..
31
3-10
Seasonal resultant wind direction for site 7 ……………………
31
3-11
Annual Percentage frequency distributions of wind directions …………………….…………………………………………………….. xii
38
………………………………………………………………………………………………………………….. List of Figures
3-12
Monthly wind roses for site 3 of the studied area……………….
39
3-13
Monthly wind roses for site 7 of the studied area……………….
42
3-14
Seasonal wind roses for site 3 of the studied area…………......
46
3-15
Seasonal wind roses for site 7 of the studied area……………….
47
3-16
Annual wind roses for sites (3 and 7) of the studied area…….
48
3-17
Topographical image for sites (3 and 7) of the studied area with annual wind roses……………………………………………………….
3-18
Diurnal wind shear exponent pattern at studied area using Eq. (2-6) ………………………………….………………………………………
3-19
55
Estimated seasonal wind shear exponent (α) using Eq. (2-6 and 2-7) …………………………………………………………………
3-24
53
Estimated monthly wind shear exponent (α) using Eqs. (2-6 and 2-7) ………………………………………………………………..
3-23
53
Annual diurnal wind shear exponent pattern at studied area using Eq. (2-7) ……………………………………………………………………..
3-22
52
Annual diurnal wind shear exponent pattern at studied area using Eq. (2-6) …………………………………..…………………………………
3-21
52
Diurnal wind shear exponent pattern at studied area using Eq. (2-7)……………………………………………………………………………
3-20
49
56
Monthly extrapolated mean wind speed from (20 to 100) m height for site 1 …………………………………………………………………
xiii
57
………………………………………………………………………………………………………………………. List of Symbols
LIST OF SYMBOLS Pressure in Pascal ( Volume (
)
)
Number of Moles Universal Gas Constant (8.3144 Absolute Temperature (
)
)
Wind Speed change with elevation Friction Velocity (m/sec) Von Karman’s constant (≈0.4) Roughness length (m) Ψ
Stability Dependent Function Wind Speed (m/sec) at height
(m) (For wind profile log-law equation)
Wind Speed (m/sec) at height
(m)
(For wind profile log-law equation)
Wind speed (m/sec) measured at anemometer height Wind speed (m/sec) to be calculated at the height
α
Wind Shear Exponent Resultant Wind Speed in the West-East Direction Resultant Wind Speed in the South-North Direction Number of observations Resultant Wind Speed of Components (
θ
Wind Direction in Degree Persistence of Resultant Wind Direction Mean Wind Speed (m/sec) Average (Mean) Speed (m/sec)
n
number of wind data Standard Deviation of Wind Speed xiv
,
)
(m) (m)
Chapter One …………………………………………………………………………………………………. Introduction
CHAPTER ONE
INTRODUCTION 1.1 WIND The wind can be defined as the movement of air in the atmosphere relative to the surface of the earth. Wind blows freely in three-dimensional space having both speed and direction, which must be considered as a vector that can be resolved into three orthogonal components. Relative to the earth, this means components in the north/south, east/west and upwards/downwards direction. Relative to an aircraft’s flight path, it means headwind/tailwind (longitudinal) components, left/right crosswind (lateral) components and updraft/downdraft (vertical) components [1].
The vertical component of the wind in the atmosphere is usually small compared with one or both horizontal components. This is especially true near the ground where the wind is constrained to move in the horizontal plane. Because the horizontal components generally predominate, it is assumed that a horizontal wind blows parallel to the earth’s surface, thereby neglecting the vertical component. Except in special cases, where the vertical component of the wind predominates; it is produced by things such as convective cloud (particularly thunderstorms), mountain waves and thermals [1].
The wind is a natural resource that has been and will always be around. It is an energy source that produces no pollutants meaningless smog, acid rain, and greenhouse gas emissions. It can be constantly exploited without the need to import energy supplies from foreign countries. Near-surface wind is an important climate parameter, which has a strong influence on human activities. Wind speed, and especially wind direction, 1
Chapter One …………………………………………………………………………………………………. Introduction
determines the general character of weather conditions. It is an important natural factor also in other kinds of human activities, as well as in everyday life of humans [2, 3].
1.2 Origin and Fundamental Causes of Wind The areas of the globe where air is descending are zones of high pressure and where the air is ascending, low-pressure zones are formed. The pressure gradient drives the flow of air from high to low pressure, thus causing the wind. There is a pressure gradient force in the vertical direction, but this is usually cancelled by the downward gravitational force. Thus, the winds blow predominately in the horizontal plane, responding to horizontal pressure gradients [4].
The basic driving force of air movement is a difference in air pressure between two regions. This air pressure is described by several physical laws. One of these is the ideal gas law: ……….. (1.1)
Where
is the pressure in Pascal (
),
is volume(
is the universal gas constant (8.3144
) and
),
is the number of moles,
is absolute temperature (
)
[5].
There are two principal reasons for the movement and the direction of motion of the Earth’s atmosphere – the unequal amounts of solar radiation received at different latitudes and the rotation of the earth. Superimposed upon the general world wind circulation, due to these two factors, modifications arise from local disturbances, such as the tropical cyclone. We have on terrestrial scale regular pressure systems that produce important winds, called dominant winds or general circulation. In practice, atmospheric circulation can be represented as it is shown in Figure (1-1) and it is useful in identifying the most important global wind characteristics [6].
2
Chapter One …………………………………………………………………………………………………. Introduction
Figure (1-1): General world wind circulation [6]
In each hemisphere, we can discern three more or less individualized cells: a tropical cell, a temperate cell, and a polar cell, which turns one against the other like cogs in a gear box. The north and the south tropical cells are separated from one another by the equatorial calm which is a low-pressure area and from the temperate cells by the subtropical high-pressure zones. Actually, the sketch is not perfect. The unequal heating of oceans and continents surface, relief, vegetation, and seasonal variations deform and modify the high-and low-pressure zones. There are also atmospheric disturbances created by masses of cold air that move, from time to time, from the poles towards the equator. Thus, the state of the atmosphere is continually evolving [6].
1.3 Meteorology of Wind Direction and Speed Theoretically, at the Earth’s surface, the wind blows from high-pressure areas toward low-pressure areas. However, at the medium and higher latitudes, its direction is modified by the earth’s rotation. The wind becomes parallel to isobaric lines instead of being perpendicular to them. In the northern hemisphere, the wind rotates counterclockwise round cyclonic areas and clockwise round anti-cyclonic areas. In the southern hemisphere, these wind directions are reversed. The wind direction is determined by the 3
Chapter One …………………………………………………………………………………………………. Introduction
direction from which it blows. For example, it is a westerly wind if the air blows from the West [6]. There are two different types of wind which affect the earth’s atmosphere and they together determine the direction of the wind in a given area. The first form is known as Global wind which is the type of wind that appears all over the world due to the earth’s rotation around itself and the movement of earth around the sun. The global wind is not shaped by the surface of the earth because the average altitude is 1000m. These winds are influenced by temperature and pressure gradients around the world and dictate the prevailing movement of weather systems. The second one is known as Local wind or surface wind. Ground surface roughness and obstacles are the main factors that affect this type of wind; their effects can be measured at altitudes below 100 m and they are also very heavily influenced by local thermal factors. The most important local winds are monsoons, anabatic winds, katabatic winds, land breezes, sea breezes. Wind shear, turbulence and acceleration over the ridges are some other examples for local wind effects [7, 8, 9].
Another controlling factor which influences wind speeds by offsetting the pressure gradient force is friction on the earth’s surface. With increasing wind speeds, friction between the air and the surface increases. Frictional resistance to wind provided by the surface of the earth is influenced by many variables such as: elevation, terrain roughness, and local topography [10].
1.4 Wind Shear The change of wind speed and/or wind direction is called wind shear. Wind shear can be divided into vertical and horizontal shears. International Civil Aviation Organization (ICAO) defines vertical and horizontal components of wind shear as follows: Vertical wind shear is defined as change of horizontal wind direction and/or speed with height, as would be determined by means of two or more anemometers mounted at different heights on single mast and horizontal wind shear is defined as the change of 4
Chapter One …………………………………………………………………………………………………. Introduction
horizontal wind direction and/or speed with horizontal distance, as would be determined by two or more anemometers mounted at the same height along a runway [11].
Wind shear describes the fact that close to the ground, the wind is slowed down by friction and the influence of obstacles. Thus, wind speed is low close to the ground and increases with increasing height above the ground. Wind shear is more pronounced over rough terrain and less pronounced over smooth terrain. The variation of wind speed with height depends on the surface roughness and the atmospheric stability [6].
The most generalized explanation of wind shear is "a change in wind speed and/or direction in space, including updrafts and downdrafts". From this explanation it follows that any atmospheric phenomenon or any physical obstacle to the prevailing wind flow that produces a change in wind speed and/or direction, in effect, causes wind shear. Wind shear is always present in the atmosphere and its presence is often visible to an observer. Examples are cloud layers at different levels moving in different directions; smoke plumes sheared and moving in different directions at different heights; and trees bending in all directions in response to sudden gusts from a squall line. All these visual effects testify to the universal presence of wind shear and wind shear-causing phenomena in the atmosphere [1].
Wind shear, encountered near the ground, is more serious and potentially very dangerous. Vertical shear is most common near the ground and can pose a serious hazard to aircrafts during takeoff and landing [12].
1.5 Literature Review Many recent studies have investigated wind characteristics. Analyses of wind characteristics have been conducted at different temporal scales, such as yearly, seasonal and monthly, based on the time scale of the wind data from the region [13]. 5
Chapter One …………………………………………………………………………………………………. Introduction
Many studies of wind characteristics have been conducted in many countries worldwide. Keyhani et al. conducted a study using statistical data from eleven years of wind speed measurements from Tehran, the capital of Iran, to determine the wind energy potential. For evaluating wind direction, it was found that the most probable wind direction for the eleven-year period is on 180 degree [14]. Mirhosseini et al. analyzed wind speed data that were recorded every three hours from 2003–2007 at 10 m, 30 m and 40 m heights in the Semnan Province in Iran, it was found that prevailing wind directions are about (200–260) degree for 30 m height and as an obvious result for 37.5 m height; which is generally at Southwest direction for most of the months [15].
Jaak and Ain analyzed long-term changes in the occurrence of different near surface wind directions in homogeneous time series (were studied during 1966-2008) from 14 stations of Estonia, and relationships between the indices of large-scale atmospheric circulation and near-surface wind directions. There, significant alterations in wind directions were determined, and found to be the strongest in the winter season [3]. Patrici A L Danyelle Lewis studied Monthly- Annual Wind Data (2004-2010). He used an evaluation version of the Wind Rose Pro software to determine and analyze the runway orientation of O’Hare runways. It was found that the wind blowing at O'Hare airport has a southern directional bias only two of the eight runways meet the criteria of a northeast/southwest direction. The directions of the winds are predominantly southerly headings and wind speeds are greater than 7 m/s [16].
Ahmed Shata analyzed Potential wind power generation in South Egypt. The diagrams of the measured wind data for three meteorological stations over a period of two years (wind speed, frequency and direction), wind shear coefficient, and the mean monthly and annual wind speed profile for every location are presented. A comparison of the rose diagrams shows that the wind speed is more persistent and blows over this region of Egypt in two main sectors N and NNW with long duration of frequencies from 67% to 87% over the year with an average wind speed in the range 6.8–7.9 m/s at the three stations [17]. J.N. Kamau et al. used wind data from the Kenya Meteorological 6
Chapter One …………………………………………………………………………………………………. Introduction
department for the period (2001–2006) to study the Diurnal, monthly and inter-annual variability using empirical method (Power law) and the wind rose analysis revealed no marked variation in wind direction and frequency throughout the year (mean direction between 150 and 160 degrees with highest standard deviation of 33.5 degrees) [18].
M.L. Ray et al. determined the accuracy of commonly used wind shear models and methods, especially when used with wind data from sites having hills and/or forests. They also found that there is not a significant difference in the performance between the log and power laws. It was found that the one-seventh power law could not represent the wind shear for the flat sites, and also generally accepted that wind shear trends are not necessarily true [19]. Teolan and Hannu determined that the period of variation of the Hellmann coefficient for one year. Based on the wind speeds, which were recorded at different heights, no single reason of the alternation of the wind shear curvature was established. Most probably it is caused by a complex of physical processes, like changes in the wind speed and direction, and also by the surrounding landscape [20].
Shafiqur Rehman analyzed long term wind data in terms of annual, seasonal and diurnal variations at Yanbo, which is located at the west coast of Saudi Arabia. The wind speed and the wind direction hourly data for a period of 14 years between 1970 and 1983 is used in the analysis, it was found that higher values of wind during the summer months and smaller values during the winter months, wind speed reach 5.0 m/s and more during the March–September months and the diurnal trend of wind speed of the order of 5.0 m/s and reaching 8.0 m/s were between 12:00 and 21:00 hour [21]. Giovanni Gualtieri and Sauro Secci calculated wind shear coefficients (WSCs) based on one hour measured wind data has been performed by three stations located over coastal sites in Southern Italy. In addition, a detailed analysis has been carried out to describe the wind shear coefficient yearly, monthly and diurnal variation, as well as by wind direction, also and evaluating wind resource by means of wind roses and wind speed frequency distributions at 50-m [22].
7
Chapter One …………………………………………………………………………………………………. Introduction
Ahmed R. (2006) studied six locations (stations) within Erbil Governorate, Kurdistan Region. The annual and monthly mean wind speeds were found, at 10 m height the values of the annual mean wind speed ranging from (0.98 to 4.40) m/sec and the mean monthly wind speed ranging from (0.71 to 6.29) m/sec at Degala and Shaqlawa stations respectively. The values of the estimated exponent power (α) were ranging from (0.32 to 0.39) [23]. Salahaddin and Meeran analyzed the wind characteristics and estimated the wind direction for a Kalar region, located in southern Sulaimani city of the North Iraq. Specific hourly wind speeds and wind directions, based on one year (2003), were used to generate monthly, seasonal and annual wind roses charts for the studied area. The summary statistics for the seasonal and annual data for the surface wind speeds at 10 meters were presented and shown that the wind roses depend on spatial wind pattern and the prevailing wind direction between north and east [24].
1.6 Objectives
The aims of this study are to analyze and estimate the mean wind speeds (monthly, seasonally, and annual) and to determine the prevailing wind directions (monthly, seasonally, and annual) using wind rose diagram. It is also to estimate the wind shear exponent using two different methods and calculating the vertical wind shear by extrapolating the wind speed recorded at 20 meters above ground level to 100 meters for the studied area using power-law equation.
8
Chapter Two ………………………………………………………………………………………………………… Theory
CHAPTER TWO
THEORY 2.1 Atmospheric Boundary Layer
Atmospheric boundary layer is the part of the troposphere that is directly influenced by the presence of the earth’s surface, and responds to surface forcing with a timescale of about an hour or less. The atmospheric boundary layer thickness varies greatly depending on external factors, and ranging from some hundreds of meters to 3 kilometers [25, 26].
Above the atmospheric boundary layer is the free atmosphere where atmospheric parameters, such as humidity and temperature are no longer affected by the surface environment. Equally the wind speed and direction is no longer affected by surface friction and is now considered geostrophic, which means that the Coriolis force and pressure gradient force governs it, as shown in figure (2-1) [25].
Figure (2-1): The troposphere can be divided into two parts: a boundary layer (shaded) near the surface and the free atmosphere above it [26]
9
Chapter Two ………………………………………………………………………………………………………… Theory
In the lowest layer of the atmosphere, below about 100 m, the wind direction is approximately constant with height while the wind speed is observed to increase with height, the change being most rapid immediately above the surface. The derivation, from physical principles, of a theoretical relationship between wind speed and height in the surface boundary layer under all possible stability conditions presents some difficulties. Above the surface boundary layer, from about 100 m up to about 600 m, is the Ekman layer, where the effect of friction on the wind decreases rapidly with height and the horizontal pressure gradient and coriolis forces become increasingly dominant. As in the case of the surface boundary layer, the wind speed between 100 m and 600 m increases with height as the effect of friction decreases. However, the wind direction does-not remain constant with height, as was assumed in the surface boundary layer, but veers (back) with height in the northern (southern) hemisphere [1].
2.2 Wind Profile The relation between wind speed and height is called the wind profile. The wind speed increases with height. This increase depends on the friction against the surface. Over flat terrain with low friction (water), the wind is not affected so much and the increase with height is not very big. Over a surface with high roughness ʹcity and farmʹ, the wind speed increases more significantly with height, as shown in figure (2-2) [27].
Figure (2-2): Wind Profiles [27] 10
Chapter Two ………………………………………………………………………………………………………… Theory
2.2.1 Wind Profile Log-Law The logarithmic law vertical wind profile is derived theoretically from the basic principles of fluid mechanics and the concept of atmospheric stability. The log wind profile is a mathematical relationship which is used to approximate the general logarithmic profile of wind speeds as they increase with increasing distances from the ground [28]. The wind speed change with elevation ( ) was introduced by Prandtl (1932) and is usually expressed as: [29] . . . . . . . . . . . . . . . . (2-1) Where
is the friction velocity,
is von Karman’s constant (≈0.4) and is the height
The logarithmic wind profile equation is derived from the integration of Eq. (2-1) over height from
to any height [29]. . . . . . . . . . . . . . . . (2-2)
Where
is the roughness length of the terrain (in meter), which in principle can only be
applied under neutral stability conditions [22].
The effects of the atmospheric stability could be added by including an extra term into the profile:
[ Where
]
. . . . . . . . . . . . . . . (2-3)
is a stability dependent function, positive if the atmosphere is unstable and
negative for stable conditions.
At a special case the wind speed from a known reference height can be used to calculate the wind speed at another height using the following logarithmic formula: [28] 11
Chapter Two ………………………………………………………………………………………………………… Theory
( )
………….. (2-4)
( )
Here
is the predicted wind speed at height
height
, and
,
is the known wind speed at a
is the roughness length at the site of interest. This relation is valid at
heights between ≈ 20
and ≈100 m [8, 28].
The logarithmic wind law Eq. (2-2) fits the observed wind speed profile in the surface boundary layer very well as long as the condition of neutral stability is fulfilled. In cases where the surface boundary layer is unstable, the shear in wind speed with height will be less than that predicted by the Eq. (2-2); when conditions are stable, the shear will be higher than that predicted by the same equation, as show in figure (2-3) [1].
Figure (2-3): Neutral, stable and unstable of wind profile [30]
It is important to note that log law is weak because it cannot be used to represent the wind shear for all conditions. That is, the log law is mathematically undefined for time periods where the wind speeds at two different heights are the same [19].
12
Chapter Two ………………………………………………………………………………………………………… Theory
2.2.2 Wind Profile Power Law In some cases, serious mathematical difficulties are presented when trying to calculate logarithmic velocity profiles, therefore, sometimes simpler approximations are required in order to facilitate the calculations. The power law equation is a simple useful model of the vertical wind profile which was first proposed by Hellman (1916), derived empirically and that represents atmospheric wind profiles under atmospheric conditions where stability is not neutral [1, 29].
Since most of the available wind speed measurements have been made close to the ground, it is necessary to extrapolate the wind speed profile within the surface boundary layer. The wind speed increases with height. When record of wind speed exists at different height for a station, the commonly power law can be used to obtain the extrapolated values of wind speed at different heights: [31, 32]
( ) Where
. . . . . . . . . . . . . . . (2-5)
is the wind speed measured at anemometer height
be calculated at the height
,
is the wind speed to
, α is the wind shear exponent obtained empirically [32]. ( ⁄ )
. . . . . . . . . . . . . . . (2-6) (
⁄
)
2.3 Determination of the Wind Shear Exponent (α) A wind shear exponent (α) is not constant and depends on numerous factors, including atmospheric conditions, time of day, season, wind speed, nature of terrain, temperature, mechanical mixing parameters and wind shear exponent can also differ by measurement heights. Early assumptions by von Karman showed that under certain conditions α is equal to1/7. This value is often used in practical situations to estimate the vertical wind
13
Chapter Two ………………………………………………………………………………………………………… Theory
profile. However, studies have shown that α can change from less than 1/7 to more than 1/2 for some different types of terrain [4, 28, 33].
In addition to this, according to the 14th edition of the Wind Resource Analysis Program (WRAP) report; 7082 different wind shear exponents were calculated from the measurements performed in 39 different regions. The calculations showed that 7.3% of wind shear exponents were distributed between 0 and 0.14, and 91.9% of them were above 0.14; while a 0.8% of wind shear exponents were calculated as negative [34,35]. A number of models have been proposed for variation of (α) with these variables;
2.3.1 Justus and Mikhail Method
Justus and Mikhail (1976) used a least–square fit to observations and obtained the formula [8]. [
( [
Where
)]
(
)]
. . . . . . . . . . . . . . . (2-7)
(m/sec) is the winds speed at the reference height
(m).
2.3.2 The (1/7) Power Law Method Some researchers also found discrepancies with the Justus and Mikhail method and went on to suggest that α =1/7 should be used [8].
( )
⁄
. . . . . . . . . . . . . . . (2-8)
This 1/7 power law comes from laboratory studies and has been found to give a good approximation of the wind profile in the neutral atmospheric boundary layer. They argue that the 1/7 power law should give conservative but reasonable wind power estimates for most aero-generator sites. The two methods outlined above do not incorporate the stability and roughness dependence of (α). 14
Chapter Two ………………………………………………………………………………………………………… Theory
2.3.3 The Roughness Length Method
For practical estimation of wind climate and wind structure at some places, one needs at least to know the average wind speed either climatologically or actually observed and information on its modification by the local terrain. There are many situations where terrain influence can be summarized by way of a simple roughness parameter. The roughness is best parameterized by the roughness length
which can easily be defined
from the relative change of average wind speed V with height Z in neutral stability at levels well above the roughness elements, so the exponent (α) of the power law profile, related to
by [8]
(
√
)
………… (2-9)
Numerically, its value lies in the range of (0.1-0.50). Table (2-1) shows typical values of wind shear exponent (α) for different types of surfaces and conditions.
Table (2-1) Wind shear exponent (α) of various terrains [8] α
Terrain type
0.10 0.13 0.14 0.15 0.16 0.19 0.20 0.25 0.28 0.30 0.32 0.40
(Open water), lake, ocean, sand and smooth land ground Mown grass Neutral stability condition.(1/7)power law Foot high grass on level ground (smooth, level, grass covered) Low land, fields High grass Tall crops, hedges, and shrubs row crops Wooded country with many trees Villages and spread houses Small town with some trees and shrubs Suburb City area with tall building This may be found between (30 and 150) meters and in extreme case
0.50-1.00
15
Chapter Two ………………………………………………………………………………………………………… Theory
2.4 Mean Wind Speed Direction The mean wind is normally computed by components. The components of the mean wind along any orthogonal directions are equal to the simple means of the individual wind components along the same directions. The directions along which the components are taken are most commonly chosen as the West-East and South-North directions, when the wind is given to 8 points only; the computation then becomes particularly simple. If
is the component of the resultant wind in the west-east direction, and
the
component in the south-north direction, these components are given by [8, 36], ∑ ∑
Where
∑ ∑
(∑
∑
(∑
∑
)
(∑
)
∑
(∑
∑
) )
. . . . . . . . . . . (2-10) . . . . . . . . . . . (2-11)
in the denominators is the number of observations.
The speed of the resultant wind R is given by:
(
)
⁄
. . . . . . . . . . . . . . (2-12)
and the direction Ɵ can be expressed as: . . . . . . . . . . . . . . . . (2-13) In these equations, W stands for the speed of each individual west wind, SE for the magnitude of each individual south-east wind and so forth.
2.5 Persistence of Direction To estimate the persistence of the resultant wind direction, it is convenient to define persistence
as [8, 37] . . . . . . . . . . . . . . . . . . (2-14)
Where
mean wind speed.
16
Chapter Two ………………………………………………………………………………………………………… Theory
If the wind always blows from the same direction, the persistence is equal to one, (
). If it is equally likely from all directions or blows half the time from one direction
and half the time from the opposite, it is equal to zero, (
). In general, a statement
of the resultant wind or the prevailing wind direction without the statement of persistence of the wind means very little.
2.6 Topography
The wind is influenced by the Earth’s surface when it gets closer to the ground. In order to better understand wind power meteorology, which is related to the wind flow up to 200 meters above the surface, three categories of the topography effects should be examined [27].
2.6.1 Surface Roughness
The collective effect of the terrain surface and its roughness elements which leads to an overall retardation of the wind near the ground is referred to as the roughness of terrain. The climatological analysis of roughness elements like flora, urbanized areas, soil and water surface and their sizes, determine the roughness of the area, as shown in figure (2-4) [8, 27].
Figure (2-4): Roughness length [27] 17
Chapter Two ………………………………………………………………………………………………………… Theory
In most natural terrains, the surface of the earth is not uniform and changes significantly from location to location. This affects the local wind profile [4].
2.6.2 Obstacles The second category of local effects on wind flow is a different kind of obstacles, like buildings in urban area. A general classification of obstacles can be defined depending on the porosity of the obstacles that can be examined from detailed maps or by observation. Dimensions, positions and porosity of the obstacles should be taken into account when modeling [27].
2.6.3 Terrain Orography Height variations of the terrain describe the term orography. Orography can be described by height contour lines of the surface. The terrain can be classified into three general types: flat, hilly and mountainous. The terrain in which the orographic effects are insignificant and only the roughness affects the wind flow is called flat terrain, while hilly terrain represents the land where the slopes are less steep than about 0.3 [27].
Hills have a significant influence on the wind speed. A smooth and not too steep hill causes acceleration of the wind and makes the wind speed up when flowing towards the hill top, also there is a large increase in shear stress close to the ground (i.e. the wind speed increases more rapidly with height than would be the case on flat level ground), as shown in figure (2-5).
18
Chapter Two ………………………………………………………………………………………………………… Theory
Figure (2-5): Speed up effect [27]
In mountainous terrains, the slopes are steeper than in hilly terrains and it results on flow separation. In addition, the entire boundary layer is strongly influenced by the terrain. Terrain with high mountains and steep inclinations is called complex terrain. In that type of terrain, the wind flow is very hard to predict and model by linear models. For this reason, non-linear models or measurements must be used [27, 30].
2.7 Roughness Length ( ) The roughness of an area is determined by the size and the distribution of the roughness elements. Roughness is parameterized by a simple length scale, the roughness length
. This length is a mathematical factor used in the formula for logarithmic wind
profile, which shows how wind speed is influenced by the terrain [27]. The roughness length is defined as the height above ground
in meters at which the
wind speed is theoretically equal to zero. The roughness length is not constant, but varies with wind speed (
increases rapidly with increasing speed) [30, 38].
19
Chapter Two ………………………………………………………………………………………………………… Theory
There is another variable which is used to define the roughness as well, the class which is defined as: [29] (
{
( ( (
) ) )
. . . . . . . . . . . . . (2-15) )
Table (2-2) shows roughness length ( ) and their classes for varying landscape types
Table (2-2) Roughness classes and the associated roughness lengths ( ) [29, 38] Roughness Roughness Class length, (m)
Landscape Type
0
0.0002
Water surface
0.5
0.0024
1
0.03
1.5
0.055
2
0.1
2.5
0.2
3
0.4
3.5
0.8
Larger cities with tall buildings
4
1.6
Metropolitan areas with tall buildings and skyscrapers
Completely open terrain with smooth surface e.g. concrete airport runways or mowed grass. Open agricultural area without fences and hedgerows and very scattered buildings. Only softly rounded hills Agricultural land, some houses, and 8m. tall sheltering hedgerows with a distance of approx. 1250meters Agricultural land, some houses, and 8m. tall sheltering hedgerows with a distance of approx. 500 meters Agricultural land, many houses, shrubs and plants, or 8m. tall hedgerows with a distance of approx. 250 meters Villages, small towns, agricultural land with many or tall hedgerows, forests, or very rough and uneven terrain
20
Chapter Three ………………………………………………………………………………….. Results and Analysis
CHAPTER THREE
RESULTS AND ANALYSIS 3.1 Introduction In this study, four sites were chosen to analyze the wind speed, wind rose and estimating wind shear exponent of the studied area. The time series wind data recorded every one minute for the period of one year (2012) was used for this study. The geographical coordinates and height for these sites are shown in table (3-1).
Table (3-1) Geographic coordinates and height above sea level for selected sites site
Latitude
Longitude
height (m)
1
35° 34ʹ 40.7ʺ N
45° 18ʹ 42.1ʺ E
780
2
35° 34ʹ 52.3ʺ N
45° 17ʹ 50.5ʺ E
775
3
35° 34ʹ 9.5ʺ N
45° 17ʹ 3.2ʺ E
775
7
35° 32ʹ 54.2ʺ N
45° 20ʹ 29.3ʺ E
775
Sulaymanyiah International Airport is located at 35° 33´38.88”N latitude and 45° 18´52.98”E longitude with height 760 m above sea level and approximately located at 15 km west of the Sulaymanyiah city. The construction of the airport began in November 2003, and it was inaugurated in July 2005. Figure (3-1) shows the study area and location of the sites.
21
Chapter Three ………………………………………………………………………………….. Results and Analysis
Figure (3-1): Study Area and Sites Location
3.2 Average Wind Speed Analysis One of the most important pieces of information on the wind data available at a location is its average speed. In simple term, the average (mean) speed (
∑ where
) is given by [7]
. . . . . . . . . . . . . . . . (3-1)
is the wind speed and n is the number of wind data. One measure for the
variability of velocities in a given set of wind data is the standard deviation (
). Standard
deviation tells us the deviation of individual velocities from the mean value. Thus
√ Lower values of
∑
(
)
. . . . . . . . . . . . . . . . . (3-2)
indicate the uniformity of the data set.
22
Chapter Three ………………………………………………………………………………….. Results and Analysis
Figure (3-2) shows monthly variation of mean wind speed for sites 3 and 7 of the studied area. It was shown that the maximum values of the mean wind speed are for June (4.82 and 4.26) m/sec and the minimum values of the mean wind speed are for January (1.92 and 1.97) m/sec for sites (3 and 7) respectively, while the rest of the values of mean wind speed for both sites approximately equal except for months: February, March, June and July.
5.0 Site 3 Site 7
Mean wind speed (m/s)
4.5
4.0
3.5
3.0
2.5
2.0
1.5 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Months
Figure (3-2): monthly variation of mean wind speeds for selected sites of studied area
Figure (3-3) shows the seasonal variation of the mean wind speed for both sites 3 and 7. It shows the maximum and minimum values of the mean wind speed in the summer and winter seasons respectively for both sites, also showing that for all seasons the mean wind speed value of site 3 is greater than that of site 7.
23
Chapter Three ………………………………………………………………………………….. Results and Analysis
4.5 Site 3 Site 7
Mean Wind Soeed (m/s)
4.0
3.5
3.0
2.5
2.0 Winter
Spring
Summer
Autumn
Seasons
Figure (3-3): Seasonal variation of mean wind speeds for selected sites of studied area
Figure (3-4) shows monthly mean speed with the standard deviation of mean values for both sites (3 and 7). It was shown that the deviation of individual speeds from the mean values are between (0.6 to 1.85) m/sec and (0.6 to 1.6) m/sec for sites (3 and 7)
Standard Deviation of mean wind speed m/sec
respectively, which indicates the uniformity of the data set.
2.0 Site 3 Site 7
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Mean Wind Speed m/sec
Figure (3-4): Monthly St.Dev. vs Mean wind speed for site 3 and 7
24
Chapter Three ………………………………………………………………………………….. Results and Analysis
Also figure (3-5) shows seasonal mean speed with the standard deviation of mean values for both sites (3 and 7), it was shown that the deviation of individual speeds from the mean values for site 3 are between (1.05 to 1.67)m/s and more than that of site 7,
Standard Deviation of mean wind speed m/sec
which are between (0.9 to 1.25) m/s. 1.8 Site 3 Site 7 1.6
1.4
1.2
1.0
0.8 2.0
2.5
3.0
3.5
4.0
4.5
Mean Wind Speed m/sec
Figure (3-5): Seasonal St.Dev. vs Mean wind speed for site 3 and 7
3.3 Wind Speed Frequency Distribution: Wind speed frequency distribution can simply be obtained by plotting the different wind speeds against their frequencies. The sorting of the data into narrow wind speed bands is called binning (class interval) of the data. In this study, a bin width of 0.5m/sec has been used and the central value of each bin i.e. 0.25 m/sec, 0.75 m/sec etc. has been used in calculations and frequency distribution group. Figures [3-6(a, b, c, d and e)] show percentage wind frequency distribution for seasonal and annual wind speed data for sites 3 (dark blue) and 7 (blue) for the studied area. The height of each column represents the percentage frequency of wind speed, in general for both sites the all seasons have maximum percentage frequencies of wind speed at ≥4.5 m/sec except the winter has the maximum percentage frequency of wind speed
25
Chapter Three ………………………………………………………………………………….. Results and Analysis
between (1.0-1.5 and 2.-2.5) m/sec, also shown that in summer the percentage frequency of all wind speeds between (0.5-10.2) except for the wind speed (≥4.5m/sec) has the percentage frequency (41.9 and 37.9) for sites (3 and 7) respectively and the annual have the maximum percentage frequency of (27.3 and 23.2) of wind speed (≥4.5m/sec) for Winter
sites respectively. 20
Percentage Frequency
Site 3 Site 7
15
10
5
0 0 - 0.5
0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 2.0 - 2.5 2.5 - 3.0 3.0 - 3.5 3.5 - 4.0 4.0 - 4.5
>= 4.5
Wind Speed (m/s)
Figure (3-6 a): a percentage histogram for winter Spring 30 Site 3 Site 7
Percentage Frequency
25
20
15
10
5
0 0 - 0.5
0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 2.0 - 2.5 2.5 - 3.0 3.0 - 3.5 3.5 - 4.0 4.0 - 4.5
>= 4.5
Wind Speed (m/s)
Figure (3-6 b): a percentage histogram for spring 26
Chapter Three ………………………………………………………………………………….. Results and Analysis
Summer 50 Site 3 Site 7
Percentage Frequency
40
30
20
10
0 0 - 0.5
0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 2.0 - 2.5 2.5 - 3.0 3.0 - 3.5 3.5 - 4.0 4.0 - 4.5
>= 4.5
Wind Speed (m/s)
Figure (3-6 c): a percentage histogram for summer
Autumn 25 Site 3 Site 7
Percentage Frequency
20
15
10
5
0 0 - 0.5
0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 2.0 - 2.5 2.5 - 3.0 3.0 - 3.5 3.5 - 4.0 4.0 - 4.5
>= 4.5
Wind Speed (m/s)
Figure (3-6 d): a percentage histogram for autumn
27
Chapter Three ………………………………………………………………………………….. Results and Analysis Annual 30 Site 3 Site 7
Percentage Frequency
25
20
15
10
5
0 0 - 0.5
0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 2.0 - 2.5 2.5 - 3.0 3.0 - 3.5 3.5 - 4.0 4.0 - 4.5
>= 4.5
Wind Speed (m/s)
Figure (3-6 e): Annual percentage histogram
3.4 Persistence of Direction The measurement of wind speed and direction are highly sensitive to flow distortion by obstacles. For this work, the directions along which the components are taken are 8 sectors as shown in table (3-2) and they are most commonly chosen as the West-East and South-North directions. The direction of the resultant wind speed (Ɵ) and the persistence of the resultant wind direction ( ) are estimated using equations (2-13) and (2-14) respectively.
Table (3-2) Eight circular direction sectors system [8] Direction Circular Directional Sectors Sectors (Degree) N 337.5 → 22.4 NE 22.5 → 67.4 E 67.5 → 112.4 SE 112.5 → 157.4 S 157.5 → 202.4 SW 202.5 → 247.4 W 247.5 → 292.4 NW 292.5 → 337.4 28
Chapter Three ………………………………………………………………………………….. Results and Analysis
Figures (3-7 and 3-8) show monthly resultants of wind direction for both sites (3 and 7) respectively. From the figure (3-7), it can be seen that the values of resultant wind direction of January, March, April, May, June, July, October and December are between (7.7 to 85) degrees with persistence percentage 26.45, 40.72, 19.22, 67.4, 85.2, 54.19, 7.72 and 26.4 respectively. From figure (3-8), it can be seen that the values of resultant wind direction of months April, May, June, July, august, September and October are between (271.7 to 358.46) degrees with persistence percentage 17.3, 70.8, 91.43, 62.44, 96.12, 73.76 and 9.64 respectively.
Figure (3-7): Monthly resultant wind direction for site 3
29
Chapter Three ………………………………………………………………………………….. Results and Analysis
Figure (3-8): Monthly resultant wind direction for site 7
Figures (3-9 and 3-10) show seasonal resultants of wind direction for both sites (3 and 7) respectively. From figure (3-9), it can be seen that the values of resultant wind direction of the winter and summer were between (274 and 350) degrees with persistence percentage (19.14 and 60.04) respectively and for both spring and autumn were between (25 and 65) degrees with persistence percentage (40.24 and 21.71) respectively. From figure (3-10), it can be seen that the values of resultant wind direction of seasons: winter and spring were between (78 and 88) degrees with persistence percentage (13.14, 38.3) respectively and for summer and autumn were between (335 and 355) degrees with persistence percentage (72.05 and 29.1) respectively.
30
Chapter Three ………………………………………………………………………………….. Results and Analysis
Figure (3-9): Seasonal resultant wind direction for site 3
Figure (3-10): Seasonal resultant wind direction for site 7
31
Chapter Three ………………………………………………………………………………….. Results and Analysis
Table (3-3) shows the monthly values of (
,
, , Ө, mean V and
) for sites 3 and 7
of the studied area. This table indicates that the values of the resultants of wind direction (Ɵ) (296.4 and 295.3) degrees in August had maximum persistence (87.5% and 96.1%) respectively, also table (3-4) shows the seasonal values of (
,
, , Ө, mean V and
)
for sites 3 and 7 of the studied area. This table indicates that the values of resultants wind direction (Ɵ) (349.8 and 335.6) degrees in summer season had maximum persistence (60.04% and 72.05%) respectively.
Table (3-3) Monthly and annual values of ( Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
, , Ө, mean V and Ѳ (Degree)
) for site 3 and 7 (m/s)
site 3
site 7
site 3
site 7
site 3
site 7
site 3
site 7
site 3
site 7
site 3
site 7
0.44
0.41
0.25
0.21
0.51
0.46
60.1
63.1
1.92
1.97
26.5
23.4
-1.39
-1.20
0.04
-0.05
1.39
1.20
271.7
87.5
3.55
3.22
39.3
37.1
0.90
0.83
1.22
0.78
1.52
1.14
36.3
46.8
3.73
3.41
40.7
33.5
0.47
0.48
0.27
-0.02
0.55
0.49
59.9
272.3
2.85
2.81
19.2
17.3
2.18
2.13
0.19
-0.06
2.19
2.13
85.0
271.7
3.25
3.01
67.4
70.8
-1.17
0.10
-3.94
-3.89
4.11
3.90
16.5
358.4
4.82
4.26
85.2
91.4
-0.49
0.20
-2.38
-2.50
2.43
2.51
11.5
355.4
4.48
4.02
54.2
62.4
2.95
3.19
-1.47
-1.51
3.30
3.53
296.4
295.3
3.77
3.67
87.5
96.1
0.35
1.08
-2.19
-2.39
2.21
2.63
350.9
335.7
3.69
3.56
60
73.8
0.03
0.23
0.23
-0.17
0.23
0.29
7.7
306.5
2.99
2.96
7.72
9.64
-1.26
-1.07
0.12
-0.05
1.27
1.07
275.2
87.3
2.58
2.42
49.1
44.1
-0.57
-0.26
-0.19
-0.19
0.60
0.32
71.7
53.1
2.28
2.23
26.4
14.5
0.22
0.53
-0.64
-0.81
0.68
0.97
340.9
327
3.32
3.12
20.5
31
Table (3-4) Seasonal values of ( Season
,
,
, , Ө, mean V and
) for site 3 and 7
Ɵ (Degree)
(m/s)
site 3
site 7
site 3
site 7
site 3
site 7
site 3
site 7
site 3
site 7
site 3
site 7
Winter
-0.49
-0.33
0.04
-0.01
0.49
0.33
274.1
88.1
2.56
2.45
19.14
13.4
Spring
1.19
1.16
0.57
0.24
1.32
1.18
64.7
78.5
3.28
3.08
40.24
38.33
Summer
0.46
1.18
-2.57
-2.61
2.61
2.87
349.8
335.6
4.35
3.98
60.04
72.05
Autumn
-0.29
0.08
-0.60
-0.86
0.67
0.87
25.7
354.6
3.09
2.98
21.71
29.1
32
Chapter Three ………………………………………………………………………………….. Results and Analysis
3.5 Wind Direction Analysis To give the information about the distribution of wind speeds and the frequency of the varying wind directions of the studied areas, one may draw a so-called Wind Rose on the basis of meteorological observation of wind speeds and wind directions. A wind rose is a polar plot which represents the percentage of time that the wind direction falls within each sector of the compass. Where the wind direction is shown over a period, the value represents the vector sum for the period. The wind rose only tells one the relative distribution of wind directions not the actual level of the mean wind speeds [8, 18]. To analyze wind direction, in this study the compass is divided into 12 sectors, as shown in table (3-5), one for each 30 degrees of the horizons. The software used to generate these high-quality wind roses is courtesy of Lakes Environmental Software and is called WR-PLOT, version 7 [39]. In order to construct wind roses and analyze the frequency distribution, all data of time series were used during one year (2012) of wind speed and wind direction for both sites (3 and 7). Table (3-5) Twelve circular direction sectors system [21] Direction sectors
Circular Directional sectors (Degree)
N
345.00 - 15.00
NNE
15.00 - 45.00
ENE
45.00 - 75.00
E
75.00 - 105.00
ESE
105.00 - 135.00
SSE
135.00 - 165.00
S
165.00 - 195.00
SSW
195.00 - 225.00
WSW
225.00 - 255.00
W
255.00 - 285.00
WNW
285.00 - 315.00
NNW
315.00 - 345.00
33
Chapter Three ………………………………………………………………………………….. Results and Analysis
Tables (3-6 and 3-7) show monthly mean wind speed with percentage frequency distribution of directions at 15 m height for sites 3 and 7 respectively. Table (3-6) indicates that the value of mean wind speed during August 3.77 m/sec has the highest frequency occurrence with (21.37%) in WNW direction sector during the year. Table (3-7) indicates that the value of mean wind speed during August 3.67 m/sec has the highest frequency occurrence with (27.38%) in WNW direction sector during the year.
Tables (3-8 and 3-9) show the seasonally mean wind speeds with percentage frequency distribution of directions for both sites 3 and 7 respectively. Table (3-8) indicates that the value of mean wind speed during summer 4.35 m/sec has the highest frequency occurrence with (16.68%) in WNW direction sector. Table (3-9) indicates that the value of mean wind speed during summer 3.98 m/sec has the highest frequency occurrence with (20.56%) in WNW direction sector.
34
Chapter Three …………………………………………………………………………………………………………………………………………………….. Results and Analysis
Table (3-6) Monthly mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 3 Month
Mean wind speed(m/s)
January
Percentage frequency of winds blowing from the following directions N
NNE
ENE
E
ESE
WNW NNW
Calm
1.92
7.76
3.28
2.23
4.47 11.31
8.94
3.28 5.13
8.81
11.05 11.71 17.89
1.97
February
3.55
5.86
4.72
4.87
7.72
10.3
7.58
4.57 7.29
9.01
8.72
6.86
11.44
0.57
March
3.73
4.27
3.47
6
6.54 10.28
9.61
4.53 9.61 12.55
8.01
9.87
13.35
1.2
April
2.85
9
4.43
4.15
3.6
12.18
8.72
4.29 6.09
11.77 13.71 12.46
0.83
May
3.25
6.26
3.06
4.53
5.2
9.86
3.86
6.93 12.13 15.46 15.73 13.46
0.67
June
4.82
4.54 12.64 18.46 7.38
2.98
3.26
1.27 3.12
5.82
11.5
15.48 13.06
0.43
July
4.48
6.97 12.19 12.19 4.42
4.96
5.36
2.81 5.63
8.31
13
13.13 10.32
0.4
August
3.77
6.45
4.83
5.24
2.28
2.01
3.89
3.22 5.77
7.39
19.22 21.37 17.74
0.54
September
3.69
6.32
9.62
9.76
3.3
3.3
7.01
3.85 3.85
7.84
10.72 17.19 15.81
0.41
October
2.99
5.9
5.23
5.23
6.3
9.66
10.46
5.1
4.56
8.59
12.88 11.67 13.02
1.21
November
2.58
6.03
3.29
6.44
9.32 14.81 12.07 3.42 3.42
5.9
7.95
11.93 13.03
1.1
December
2.28
7.61
6
4.4
6.54
6.81
8.68
13.48 15.08
1.34
9.47
35
SSE
11.48
S
2
3.6
SSW WSW
4.8
8.44
W
Chapter Three …………………………………………………………………………………………………………………………………………………….. Results and Analysis
Table (3-7) Monthly mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 7 Month
Mean wind speed(m/s)
January
Percentage frequency of winds blowing from the following directions N
NNE
ENE
E
ESE
SSE
S
W
WNW NNW
Calm
1.97
7.52
4.43
2.28
4.3
16.13
9.67
3.63
3.9
6.05
9.94
17.07 13.03
2.02
February
3.22
4.45
10.9
10.47 6.17 18.08
7.17
3.3
5.88
7.03
7.6
10.47
6.46
1.87
March
3.41
5.35
9.63
4.15
6.02 12.31
7.09
4.95 8.43
9.5
12.45 11.24
7.63
0.8
April
2.81
5.41
5.13
4.85
6.38 13.45
8.18
5.41 5.13
5.96
11.51 17.34 10.26
0.83
May
3.01
4.07
5.37
4.57
4.03
7.8
6.45
3.36 5.37
8.87
18.28 18.68 11.42
1.08
June
4.26
6.1
19.46 15.05 3.83
2.27
1.42
1.56
1.7
5.25
12.21 21.02
0.14
July
4.02
5.91 17.74 11.69 4.97
3.63
3.76
2.55 4.03
8.46
13.17 13.31 10.75
0
August
3.67
3.89
6.98
4.56
1.88
3.09
3.62
3.49
5.1
6.04
18.92 27.38 14.09
0.81
September
3.56
5.36
14.3
7.7
4.4
4.81
4.13
2.61 3.03
5.91
11.28 22.97 12.24
0.28
October
2.96
4.97
8.2
9.14
6.05 11.42
8.06
3.76 4.57
4.84
11.16
17.6
9.54
0.67
November
2.42
5.69
8.46
5.69
7.35 19.28 11.37 4.16 2.22
3.05
8.87
13.59
7.9
2.22
December
2.23
5.75
7.49
3.08
5.35 16.33
4.41
10.71 16.86 10.84
36
10.3
SSW WSW
3.08 3.34
9.94
2.01
Chapter Three …………………………………………………………………………………………………………………………………………………….. Results and Analysis
Table (3-8) Seasonal mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 3 Mean wind Percentage frequency of winds blowing from the following directions Seasons speed(m/s) N NNE ENE E ESE SSE S SSW WSW W WNW NNW Calm Winter
2.56
7.11
4.66
6.97
6.2
10.37 9.37
3.8
5.7
8.2
9.51
10.78
14.9
1.31
Spring
3.28
6.48
3.64
4.9
5.13
10.76 7.38
3.6
7.56 11.07 11.75
13.1
13.1
0.9
Summer
4.35
6.01
9.84
11.85
4.65
3.32
4.19 2.46 4.87
7.2
14.63
16.68 13.72
0.46
Autumn
3.09
6.09
6.04
17.13
6.31
9.26
9.86 4.13 3.95
7.45
10.54
13.58 13.94
0.91
Table (3-9) Seasonal mean wind speed and percentage frequency distributions of wind direction (at a height of 15 m) for site 7 Mean wind Percentage frequency of winds blowing from the following directions Seasons speed(m/s) N NNE ENE E ESE SSE S SSW WSW W WNW NNW Calm Winter
2.45
5.94
7.54
5.16
5.25
16.82 9.09 3.33 4.34
5.8
9.46
14.9
10.19
1.97
Spring
3.08
5.15
6.73
4.52
5.47
11.16 7.23 4.56 6.33
8.13
14.1
15.73
9.76
0.9
Summer
3.98
5.29
14.63
10.35
3.55
3.01
2.96 2.55 3.64
6.61
14.82
20.56
11.62
0.32
Autumn
2.98
5.33
10.31
7.52
5.93
11.81 7.84 3.51 3.28
4.6
10.44
18.06
9.9
1.05
37
Chapter Three …………………………………………………………………………………. Results and Analysis
Figure (3-11) shows annual percentage frequency distribution of winds blowing from the sectors direction at a height of 15 m for both sites 3 and 7. This figure illustrated that the highest percentage frequency distribution of wind direction for site 3 stands on NNW sector direction with a value 13.91 and WNW sector direction with a value 13.53 i.e. the wind in site 3 of the studied area are predominantly north-northwest and westnorthwest, while for site 7 stands on WNW sector direction with a value 17.31 i.e. the Annualwest-northwest. wind in site 7 of the studied area is predominantly 20 Site 3 Site 7
Percentage Frequency Distribution
18 16 14 12 10 8 6 4 2 0 N
NNE ENE
E
ESE SSE
S
SSW WSW W WNW NNW
Wind Direction
Figure (3-11): Annual Percentage frequency distributions of wind directions
Figures (3-12 and 3-13) show monthly wind roses for both sites (3 and 7) of studied area respectively. In both figures, for all months the resultant vectors of wind direction were between west and north except for February and November were between north and east and March were between south and west. Figure (3-12) shows that the resultant vector with maximum value was 49% in August with direction 298 degree and figure (3-13) shows that the resultant vector with maximum value was 49% in August with direction 298 degree as summarized in table (3-10).
38
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
20%
16%
16%
12%
12%
8%
8%
4%
4%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 294 deg - 21%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
3.0 - 3.5
48 deg - 5%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 1.97%
Calms: 0.57%
January
February
NORTH
NORTH
15%
15%
12%
12%
9%
9%
6%
6%
3% WEST
3%
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 244 deg - 13%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
289 deg - 17%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 1.20%
Calms: 0.83%
March
April
Figure (3-12): Monthly wind roses for site 3 of the studied area
39
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
20%
16%
16%
12%
12%
8%
8%
4%
4%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector
3.5 - 4.0
Resultant Vector
3.0 - 3.5
287 deg - 30%
SOUTH
3.0 - 3.5
352 deg - 33%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.67%
Calms: 0.43%
May
June
NORTH
NORTH
15%
25%
12%
20%
9%
15%
6%
10%
3% WEST
5% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector
3.5 - 4.0
Resultant Vector
3.0 - 3.5
331 deg - 23%
SOUTH
3.0 - 3.5
298 deg - 49%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.40%
Calms: 0.54%
July
August
Figure (3-12): Continued
40
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
15%
16%
12%
12%
9%
8%
6%
4%
3%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s) >= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
3.5 - 4.0
Resultant Vector 320 deg - 31%
Resultant Vector
3.0 - 3.5
SOUTH
3.0 - 3.5
285 deg - 13%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5 0.5 - 1.0
0.5 - 1.0
Calms: 1.21%
Calms: 0.41%
September
October
NORTH
NORTH
20%
20%
16%
16%
12%
12%
8%
8%
4% WEST
4% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 62 deg - 4%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
313 deg - 13%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 1.10%
Calms: 1.34%
November
December
Figure (3-12): Continued
41
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
20%
16%
16%
12%
12%
8%
8%
4%
4%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 297 deg - 12%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
3.0 - 3.5
77 deg - 11%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 2.02%
Calms: 1.87%
January
February
NORTH
NORTH
15%
20%
12%
16%
9%
12%
6%
8%
3% WEST
4% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 262 deg - 10%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
3.0 - 3.5
287 deg - 11%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.80%
Calms: 0.83%
March
April
Figure (3-13): Monthly wind roses for site 7 of the studied area
42
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
25%
16%
20%
12%
15%
8%
10%
4%
5%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 287 deg - 31%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
3.0 - 3.5
344 deg - 43%
2.5 - 3.0
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 1.08%
Calms: 0.14%
May
June
NORTH
NORTH
20%
30%
16%
24%
12%
18%
8%
12%
4% WEST
6% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 339 deg - 30%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
298 deg - 49%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.00%
Calms: 0.81%
July
August
Figure (3-13): Continued
43
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
25%
20%
20%
16%
15%
12%
10%
8%
5%
4%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 327 deg - 36%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
334 deg - 12%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.28%
Calms: 0.67%
September
October
NORTH
NORTH
20%
20%
16%
16%
12%
12%
8%
8%
4% WEST
4% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 78 deg - 10%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
324 deg - 8%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 2.22%
Calms: 2.01%
November
December
Figure (3-13): Continued
44
Chapter Three …………………………………………………………………………………. Results and Analysis
Table (3-10) Summarizes monthly percentage and the direction of the resultant mean wind direction:
Table (3-10) Monthly percentage and direction of the resultant mean wind direction for sites 3 and 7 Resultant Direction of resultant vectors Mean wind Data vector % (degree) speed (m/s) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
site 3
site 7
21 5 13 17 30 33 23 49 31 13 4 13
12 11 10 11 31 43 30 49 36 12 10 8
site 3 294 48 244 289 287 352 331 298 320 285 62 313
site 7
WNW ENE WSW WNW WNW N NNW WNW NNW WNW ENE WNW
297 77 262 287 287 344 339 298 327 334 78 324
WNW E W WNW WNW NNW NNW WNW NNW NNW E NNW
site 3 1.92 3.55 3.73 2.85 3.25 4.82 4.48 3.77 3.69 2.99 2.58 2.28
site 7 1.97 3.22 3.41 2.81 3.01 4.26 4.02 3.67 3.56 2.96 2.42 2.23
Figures (3-14 and 3-15) show seasonal wind roses for both sites 3 and 7 of the studied area respectively. In both figures, for all seasons the resultant vectors of wind direction were between west and north. Figure (3-14) shows that the resultant vector with maximum value 32% in summer with direction 322 degree and figure (3-15) shows that the resultant vector with maximum value 38% in summer with direction 324 degree as summarized in table (3-11).
45
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
15%
16%
12%
12%
9%
8%
6%
4% WEST
3%
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 310 deg - 11%
SOUTH
3.5 - 4.0
3.0 - 3.5
Resultant Vector
2.5 - 3.0
278 deg - 19%
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 1.31%
Calms: 0.90%
Winter
Spring
NORTH
NORTH
20%
15%
16%
12%
12%
9%
8%
6%
4% WEST
3% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 322 deg - 32%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
315 deg - 13%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.46%
Calms: 0.91%
Summer
Autumn
Figure (3-14): Seasonal wind roses for site 3 of the studied area
46
Chapter Three …………………………………………………………………………………. Results and Analysis
NORTH
NORTH
20%
20%
16%
16%
12%
12%
8%
8%
4%
4%
WEST
EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 339 deg - 5%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
282 deg - 17%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 1.97%
Calms: 0.90%
Winter
Spring
NORTH
NORTH
25%
20%
20%
16%
15%
12%
10%
8%
5% WEST
4% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 324 deg - 38%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
341 deg - 15%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.32%
Calms: 1.05%
Summer
Autumn
Figure (3-15): Seasonal wind roses for site 7 of the studied area
47
Chapter Three …………………………………………………………………………………. Results and Analysis
Table (3-11) Summarizes seasonal percentage and the direction of the resultant mean wind direction:
Table (3-11) Seasonal percentage and direction of the resultant mean wind direction for sites 3 and 7 Data Winter Spring Summer Autumn Annual
Resultant vector % site 3 site 7 11 5 19 17 32 38 13 15 18 18
Direction of resultant vectors (degree) site 3 site 7 310 WNW 339 NNW 278 W 282 W 322 NNW 324 NNW 315 NNW 341 NNW 308 WNW 319 NNW
Mean wind speed (m/s) site 3 site 7 2.56 2.45 3.28 3.08 4.35 3.98 3.09 2.98 3.32 3.12
Figure (3-16) shows annual wind roses for both sites 3 and 7 of the studied area. It was shown that the resultant vector for site 3 is 18% with prevailing direction 308 degree, while the value of the resultant vector for site 7 is 18% with prevailing direction 319 degree. NORTH
NORTH
15%
20%
12%
16%
9%
12%
6%
8%
3% WEST
4% EAST
WEST
EAST
WIND SPEED (m/s)
WIND SPEED (m/s)
>= 4.5
>= 4.5
4.0 - 4.5
4.0 - 4.5
3.5 - 4.0
Resultant Vector 308 deg - 18%
3.5 - 4.0
Resultant Vector
3.0 - 3.5
SOUTH
319 deg - 18%
2.5 - 3.0
3.0 - 3.5
SOUTH
2.5 - 3.0
2.0 - 2.5
2.0 - 2.5
1.5 - 2.0
1.5 - 2.0
1.0 - 1.5
1.0 - 1.5
0.5 - 1.0
0.5 - 1.0
Calms: 0.90%
Calms: 1.06%
Annual (site 3)
Annual (site 7)
Figure (3-16): Annual wind roses for sites (3 and 7) of the studied area
48
Chapter Three …………………………………………………………………………………. Results and Analysis
Figure (3-17) shows topographical image with annual wind roses for sites 3and 7 of the studied area. This figure shows a clear envision of the annual wind roses and its impact on the studied area.
Figure (3-17): Topographical image for sites (3 and 7) of the studied area with annual wind roses
49
Chapter Three …………………………………………………………………………………. Results and Analysis
3.6 Estimation of Wind Shear Exponent (α) In this work, to estimate the wind shear exponent (α), two formulas are used based on one-minute time series of wind speed measured at site 1 (20 m) and site 2 (15 m), then a validation was performed on an hourly average basis, one was empirically derived and was represented by equation (2-6), using mean wind speed of both sites (1 and 2), while the second was used by Justus and Mikhail for the first time at 1976, known as Justus and Mikhail method and was represented by equation (2-7). Tables (3-12 and 3-13) show estimated diurnal wind shear exponent using Eqs. (2-6 and 2-7) respectively.
Table (3-12) Estimated diurnal wind shear exponent (α) using Eq. (2-6) Hour
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
0.06 -0.08 0.07 0.25 0.16 0.28 0.08 0.21 0.12 0.07 0.08 0.06 0.27 0.39 0.56 0.32 0.20 0.30 0.29 0.08 -0.02 0.24 0.02 -0.20
0.18 -0.04 -0.10 0.02 0.38 0.17 0.13 -0.06 0.11 0.10 0.16 0.23 0.28 0.26 0.56 0.36 0.29 0.30 0.60 0.49 0.38 0.42 0.03 0.13
0.48 0.32 0.24 0.35 0.27 0.22 0.10 0.14 0.25 0.04 0.19 0.27 0.20 0.27 0.48 0.61 0.24 0.43 0.55 0.51 0.40 0.27 0.35 0.24
0.13 0.29 0.43 0.52 0.48 0.08 -0.10 -0.02 0.11 0.24 0.32 0.20 0.27 0.35 0.50 0.60 0.21 0.29 0.17 0.10 -0.01 0.21 0.20 0.57
-0.26 0.13 0.08 0.33 0.20 0.00 0.05 0.09 0.23 0.24 0.29 0.23 0.28 0.28 0.32 0.51 0.36 0.28 0.09 0.15 0.22 0.21 0.29 0.01
0.36 0.52 0.39 0.26 0.28 0.13 0.11 0.11 0.17 0.19 0.23 0.27 0.21 0.37 0.38 0.57 0.57 0.43 0.45 0.44 0.50 0.31 0.35 0.40
0.33 0.44 0.26 0.23 0.08 0.02 0.07 0.12 0.09 0.12 0.19 0.15 0.23 0.20 0.29 0.42 0.60 0.50 0.42 0.39 0.30 0.37 0.53 0.34
0.11 0.13 -0.05 0.21 0.14 0.07 0.04 0.17 0.03 0.18 0.28 0.16 0.21 0.30 0.35 0.49 0.56 0.62 0.52 0.57 0.45 0.32 0.21 0.12
0.34 0.26 0.45 0.67 0.34 0.12 0.08 -0.01 0.10 0.14 0.13 0.25 0.26 0.30 0.45 0.55 0.41 0.47 0.29 0.27 0.13 0.06 0.20 0.34
-0.01 0.18 0.41 0.37 0.33 0.12 0.05 -0.02 0.07 0.18 0.20 0.20 0.33 0.44 0.56 0.33 0.27 0.22 0.30 0.38 0.25 0.66 0.31 0.19
0.53 0.32 0.44 0.52 0.26 0.24 0.00 -0.04 -0.04 0.06 0.10 0.13 0.24 0.38 0.52 0.28 0.20 0.14 -0.03 0.00 -0.10 0.27 0.49 0.37
-0.02 0.06 0.31 0.39 0.27 0.22 0.18 0.20 0.02 0.16 0.11 0.17 0.19 0.32 0.38 0.17 0.02 0.01 -0.06 -0.16 0.04 -0.21 0.08 -0.03
50
Chapter Three …………………………………………………………………………………. Results and Analysis
Table (3-13 ) Estimated diurnal wind shear exponent (alpha) using Eq. (2-7) Hour
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
0.36 0.36 0.36 0.37 0.37 0.36 0.35 0.32 0.31 0.31 0.30 0.30 0.29 0.30 0.32 0.32 0.33 0.33 0.34 0.34 0.35 0.34 0.36 0.36
0.30 0.30 0.30 0.30 0.30 0.29 0.27 0.26 0.25 0.25 0.24 0.24 0.25 0.26 0.26 0.28 0.28 0.28 0.28 0.28 0.29 0.30 0.30 0.30
0.30 0.30 0.30 0.30 0.29 0.27 0.26 0.25 0.25 0.24 0.24 0.24 0.24 0.24 0.25 0.27 0.28 0.30 0.31 0.30 0.31 0.30 0.29 0.29
0.33 0.33 0.32 0.34 0.31 0.28 0.27 0.27 0.27 0.26 0.26 0.26 0.26 0.27 0.27 0.28 0.29 0.31 0.31 0.33 0.34 0.33 0.33 0.33
0.33 0.33 0.34 0.34 0.34 0.30 0.29 0.27 0.25 0.25 0.24 0.24 0.23 0.24 0.25 0.26 0.27 0.29 0.29 0.30 0.30 0.31 0.33 0.32
0.26 0.26 0.25 0.25 0.23 0.22 0.23 0.23 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.25 0.25 0.25 0.25 0.26 0.26
0.27 0.28 0.27 0.27 0.25 0.23 0.24 0.24 0.25 0.25 0.25 0.24 0.24 0.24 0.24 0.24 0.25 0.25 0.26 0.26 0.26 0.26 0.26 0.26
0.30 0.29 0.29 0.30 0.29 0.27 0.27 0.26 0.26 0.25 0.25 0.24 0.23 0.23 0.23 0.24 0.25 0.26 0.27 0.28 0.28 0.29 0.29 0.30
0.28 0.28 0.28 0.28 0.27 0.25 0.25 0.26 0.26 0.26 0.26 0.26 0.25 0.25 0.25 0.26 0.26 0.27 0.27 0.28 0.28 0.29 0.29 0.29
0.32 0.32 0.31 0.31 0.30 0.27 0.26 0.26 0.27 0.27 0.26 0.27 0.26 0.27 0.28 0.29 0.29 0.29 0.31 0.31 0.31 0.31 0.32 0.31
0.32 0.33 0.32 0.31 0.31 0.31 0.29 0.28 0.27 0.28 0.27 0.27 0.27 0.28 0.31 0.31 0.31 0.32 0.32 0.32 0.32 0.32 0.32 0.31
0.32 0.32 0.33 0.33 0.33 0.34 0.32 0.29 0.29 0.28 0.28 0.29 0.30 0.31 0.32 0.33 0.33 0.32 0.33 0.33 0.34 0.34 0.32 0.32
Some values of α was found to be negative, this can be explained as following: the diurnal variation of wind shear exponent (α) was strictly correlated to the diurnal heating/cooling cycle of air above the ground and thus the stability conditions and may have negative values at night and during the day this might depend on the instability of atmospheric conditions throughout the day and mountain and valley breezes. Figures (3-18 and 3-19) show diurnal wind shear exponent (α) pattern of seasonal data using Eqs. (2-6 and 2-7) respectively, for (15 to 20) m levels. Figure (3-18) illustrates that, in general, the maximum values of α between (0.55- 0.60) were found during afternoon (14:00 to 16:00 h) for all seasons except for autumn at (3:00 h) and the minimum values 51
Chapter Three …………………………………………………………………………………. Results and Analysis
of α between (-0.02 to 0.08 ) occurred at (6:00 to 7:00 h) for autumn, spring and summer and for winter occurred at (23:00 and 1:00 h), while figure (3-19) shows that, in general, the maximum values of α between (0.30 to 0.33) for autumn, winter and spring and for summer is (0.27) during night-time (between 18:00 to 3:00 h) and minimum values of α
Wind Shear Exponent
between (0.23 to 0.28) at daytime (9:00 to 13:00) for all seasons.
0.65 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 -0.05 0 1 2 3 4 5 6 7 8 9 1011121314151617181920212223 Hours
winter spring summer autumn
Figure (3-18): Diurnal wind shear exponent pattern at studied area using Eq. (2-6)
winter
0.34
spring
Wind Shear Exponent
0.32
summer
0.30
autumn
0.28 0.26 0.24 0.22 0.20 0 1 2 3 4 5 6 7 8 9 1011121314151617181920212223 Hours
Figure (3-19): Diurnal wind shear exponent pattern at studied area using Eq. (2-7) 52
Chapter Three …………………………………………………………………………………. Results and Analysis
Figures (3-20 and 3-21) show annual diurnal wind shear exponent pattern using Eqs. (2-6 and 2-7) respectively, for (15 to 20) m levels. Figure (3-20) illustrates that the wind shear exponent (α) values varying from (0.062 to 0.463) started to increase at (00:00 to 3:00 h) then decreased until minimum value (0.062) at (6:00 h) then started to increase until maximum value (0.463) at (15:00 h) then decreased to (0.236) at (23:00 h), while figure (3-21) illustrates that the wind shear exponent (α) values varied from (0.255 to 0.306). The maximum values of α was around 0.3 at nighttime (20:00 to 3:00 h) then decreased until minimum value 0.255 at (12:00 h).
Wind shear exponent
0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hours
Figure (3-20): Annual diurnal wind shear exponent pattern at studied area using Eq. (2-6)
Wind Shear Exponent
0.35
0.3
0.25
0.2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hours
Figure (3-21): Annual diurnal wind shear exponent pattern at studied area using Eq. (2-7) 53
Chapter Three …………………………………………………………………………………. Results and Analysis
Table (3-14) shows estimated monthly wind shear exponent (α) and mean wind speeds using Eqs. (2-6 and 2-7), for sites (1 and 2). From this table, it can be seen that the values wind shear exponent (α) were estimated by Eq. (2-6) increase with increasing mean wind speed, because this method depends on several factors: such as atmospheric conditions, temperature, seasons of the year, the wind speed and nature of terrain, while the values α were estimated by Eq. (2-7) decrease with increasing mean wind speed; this is due to the dependence of this method on height and inversely proportional with wind speed.
Table (3-14) Estimated monthly values of wind shear exponent (α) and mean wind speeds using Eqs. (2-6 and 2-7) SITE 1 (20m) Mean wind speed Month (m/s) 1.894 Jan
SITE 2 (15m) Mean wind speed (m/s)
Estimated α using Eq.(2-6)
Estimated α using Eq.(2-7)
1.845
0.09
0.33
Feb
3.521
3.302
0.22
0.28
Mar
3.677
3.383
0.29
0.27
Apr
2.912
2.710
0.25
0.29
May
3.288
3.088
0.22
0.28
Jun
5.071
4.628
0.32
0.24
Jul
4.584
4.246
0.26
0.25
Aug
3.981
3.681
0.27
0.26
Sep
3.903
3.608
0.28
0.27
Oct
3.079
2.865
0.25
0.29
Nov
2.673
2.543
0.17
0.30
Dec
2.264
2.187
0.12
0.32
Figure (3-22) shows the monthly variation of wind shear exponent (α) using Eqs. (2-6 and 2-7). In figure (3-22) the wind shear exponent (α) estimated by Eq. (2-6) varied from (0.09 to 0.32). The minimum value of α (0.09) was found in January and the maximum value is 0.32 in June, while the wind shear exponent (α) estimated by Eq. (2-7) varied from (0.24 to 0.33). The minimum value of α (0.24) was found in June and the maximum value is 0.33 in January. 54
Chapter Three …………………………………………………………………………………. Results and Analysis
0.35 Using Eq. (2-6) Using Eq. (2-7)
Wind Shear Exponent
0.30
0.25
0.20
0.15
0.10
0.05 Jan
Feb
Mar
Apr
May Jun
Jul
Aug Sep
Oct
Nov
Dec
Months
Figure (3-22): Estimated monthly wind shear exponent (α) using Eqs. (2-6 and 2-7)
Table (3-15) shows estimated seasonal wind shear exponent (α) and mean wind speeds using Eqs. (2-6 and 2-7), for sites (1 and 2). From this table, it can be seen that the wind shear exponent (α) had minimum values (0.16) in winter and maximum values (0.29) in summer that were estimated by Eq. (2-6), while the α had minimum values (0.25) in summer and maximum (0.30) values in winter that were estimated by Eq. (2-7). For both equations (2-6 and 2-7) the α value in spring and autumn was close to (0.24) and equal to (0.28) respectively.
Table (3-15) Estimated seasonal and annual values of wind shear exponent (α) and mean wind speeds using Eqs. (2-6 and 2-7) of studied area season Winter spring summer autumn Annual
site 1 (20m) Mean wind speed (m/s) 2.559 3.292 4.545 3.218 3.4
site 2 (15m) Estimated α Mean wind speed using Eq. (2-6) (m/s) 2.444 0.16 3.059 0.25 4.184 0.29 3.004 0.24 3.17 0.24
55
Estimated α using Eq. (2-7) 0.30 0.28 0.25 0.28 0.28
Chapter Three …………………………………………………………………………………. Results and Analysis
Figure (3-23) shows the seasonal variation of wind shear exponent (α) using Eqs. (2-6 and 2-7). This figure illustrates that the wind shear exponent (α) values estimated by Eq. (2-6), had maximum in summer and minimum in winter; this might depend on the seasonal rotation of land uses such as arable land and crops mostly affecting those areas, which leads to a z0 increase, while the wind shear exponent (α) values estimated by Eq. (27), had minimum in summer and maximum in winter 0.32 Using Eq. (2-6) Using Eq. (2-7)
0.30
Wind Shear Exponent
0.28 0.26 0.24 0.22 0.20 0.18 0.16 0.14 Winter
spring
summer
autumn
Season
Figure (3-23): Estimated seasonal wind shear exponent (α) using Eq. (2-6 and 2-7)
We preferred Justus and Mikhail method on power law method to calculate wind shear exponent for the study area because of we get more realistic values of wind shear exponent.
3.7 Estimation of Wind Shear It would be difficult to overemphasize that wind shear is a vector, and hence the speed and the direction of the two winds concerned must be taken into account. Wind shear cannot be calculated by simple scalar subtraction of the wind speeds, except in the specific case where the direction of the two winds concerned are exactly the same or are exact reciprocals. The scalar shear (i.e. direct subtraction of wind speeds taking no account of their direction) is always less than or equal to the vector shear and therefore for most cases underestimates the actual shear magnitude [1]. 56
Chapter Three …………………………………………………………………………………. Results and Analysis
3.7.1 Vertical Wind Shear To calculate vertical wind shear, two main analytical models were used to extrapolate wind speeds to greater heights: the log law was represented by equation (2-4) and the power law was represented by equation (2-5). In general, the two models have been shown to perform equivalently in shear extrapolation predictions on average. In this work, the extrapolation was estimated for site (1) from (20 to 100) meter height using Eq. (2-5). Figure (3-24) shows monthly extrapolated mean wind speed from (20 to 100) m height with estimated wind shear exponent (α) using Eqs. (2-6 and 2-7), It was shown that the values of extrapolated mean wind speeds are approximately having the same values except for November, December, January and June which are different. 9
Mean Wind Speed (m/s)
8 7 6 5 4 3 2
at 100m using estimated alpha by eq.(2-6) at 100m using estimated alpha by eq.(2-7)
1 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug Sep
Oct
Nov
Dec
Months
Figure (3-24): Monthly extrapolated mean wind speed from (20 to 100) m height for site (1)
Table (3-16) shows estimated monthly vertical wind shear for site (1) at (20 to 100) m height using Eq. (2-5) with estimated α by Eqs. (2-6 and 2-7). From this table, it can be seen that the minimum values of vertical wind shear were (0.369 * *
)
in January and maximum values (4.27 *
June for both equations respectively. 57
)
)
and (2.986 *
and (1.65 )
in
Chapter Three …………………………………………………………………………………. Results and Analysis
Table (3-16) Estimated monthly vertical wind shear at (20 to 100) m height using Eq. (2-5) with estimated α by Eqs. (2-6 and 2-7) Month
Vertical wind shear * ( ) using α estimated by Eq.(2-6)
Vertical wind shear * ( using α estimated by Eq.(2-7)
Jan
0.369
1.650
Feb
1.890
2.504
Mar
2.381
2.506
Apr
1.803
2.160
May
1.736
2.344
Jun
4.270
2.986
Jul
3.033
2.830
Aug
2.720
2.584
Sep
2.715
2.674
Oct
1.906
2.290
Nov
1.079
2.068
Dec
0.608
1.898
)
3.7.2 Horizontal Wind Shear To determine horizontal wind shear intensity this can be done by subtracting the mean wind speeds of two sites at the same levels then divided by the distance between them. In this work, two sites (3 and 7) were selected which are 5686 m distance apart. Table (3-17) shows estimated monthly horizontal wind shear intensity using mean wind speeds of both sites (3 and 7). From this table, it can be seen that the estimated values of horizontal wind shear intensity varied between minimum (0.53 * maximum (9.85 *
)
)
and
, for October and June respectively. The values of horizontal
wind shear were found very small; this is due to small change of mean wind speeds between the selected sites (3 and 7).
58
Chapter Three …………………………………………………………………………………. Results and Analysis
Table (3-17) Estimated monthly horizontal wind shear intensity using mean wind speed of sites (3 and 7) month
horizontal wind shear intensity *
Jan
0.88
Feb
5.80
Mar
5.63
Apr
0.70
May
4.22
Jun
9.85
Jul
8.09
Aug
1.76
Sep
2.29
Oct
0.53
Nov
2.81
Dec
0.88
59
(
)
Chapter Four ………………………………………………………………………. Conclusions and Suggestions
CHAPTER FOUR
CONCLUSIONS AND SUGGESTIONS 4.1 Conclusions The following conclusions can be drawn from the results of the present study. The study conducted a detailed analysis of the wind data and made the following observations:
1)
For both sites 3 and 7, the highest monthly mean wind speed was found 4.82 m/sec and 4.26 m/sec in June; while the lowest mean wind speed 1.92 m/sec and 1.97 m/sec occurred in January. A seasonal analysis indicated that the highest mean wind speed value with 4.35 m/sec and 3.98 m/sec were found in summer season, while the lowest value is in the winter season with 2.56 m/sec and 2.45 m/sec, also annual mean wind speed as 3.32 m/sec and 3.12 m/sec respectively.
2)
For both sites, all seasons have maximum percentage frequencies of wind speed (≥4.5m/sec) except the winter, which has the maximum percentage frequency of wind speeds between (1.0-1.5 and 1.5-2.0) m/sec, also in summer the percentage frequency of all wind speeds between (0.5-10.2) except for the wind speed (≥4.5m/sec) has the percentage frequency (41.9 and 37.9) and the annual percentage frequency has maximum value (27.3 and 23.2) of wind speed ≥4.5m/sec respectively.
60
Chapter Four ………………………………………………………………………. Conclusions and Suggestions
3)
For both sites 3 and 7, the monthly values of resultants wind direction (Ɵ) (296.4 and 295.3) degrees in August had maximum persistence (87.5% and 96.1%) respectively, while the seasonal resultants wind direction (Ɵ) (349.8 and 335.6) degree in summer had maximum persistence (60.04% and 72.05%) respectively.
4)
According to wind availability analysis; the seasonal prevailing wind direction at Sulaymanyiah international airport area is in west-northwest, the mean wind speed during the summer 4.35 and 3.98 m/sec has the highest frequency occurrence during the year (16.68%) and (20.56%) for sites 3 and 7 respectively, while the annual prevailing wind directions are between north-northwest with frequency occurrence (13.91%) and west-northwest with frequency occurrence (13.53%) for site 3 and west-northwest with frequency occurrence (17.31%) for site 7.
5)
Wind Rose analysis showed that for both sites 3 and 7 the resultant vector of wind direction was fairly consistent between 278 and 360 degree which is generally from the west to north for annual, seasons and most of the months. For both sites, the monthly resultant vector had maximum value 49% in August with direction 298 degree, the seasonal resultant vector had maximum value (32% and 38%) in summer with direction (322 and 324) degree respectively and the annual resultant vector is 18% with direction 308 and 319 degrees respectively.
6)
The wind shear exponents (α) are significantly influenced by the diurnal heating and cooling cycle and varied depending on the months and seasons, the monthly values of wind shear exponent estimated by equations 2-6 and 2-7 was found, between (0.09 in January to 0.32 in June) and (0.24 in June to 0.33 in January) respectively, the seasonal values of (α) between (0.16 in winter to 0.32 in summer) and (0.25 in summer to 0.30 in winter) and the annual values of (α) were 0.24 and 0.28 respectively.
61
Chapter Four ………………………………………………………………………. Conclusions and Suggestions
7)
The monthly vertical wind shear values for site (1) at (20 to 100) m height were found that the minimum value (0.369 * and maximum value (4.27 *
)
)
and (1.65 *
and (2.986 *
)
)
in January
in June. Also the
horizontal wind shear intensity values was found varied between minimum (0.53 *
)
and maximum (9.85 *
)
for October and June respectively.
The values of horizontal wind shear were found very small; this is due to small change of the mean wind speeds between the selected sites (3 and 7).
4.2 Suggestions for Future Works:
1) Similar study can be implemented in the other locations to be compared with the present work. 2) This study may provide information for developing wind energy in studied area and the works may be continued in the future including the power generation by the wind turbine.
3) Study can be conducted in the future related to the hazards wind speed and direction on aircraft in sulaymanyiah international airport.
62
………………………………………………………………………………………………………………………. References
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66
ملخص في هذه الدراسة ،تم تحليل خصائص الرياح السنوية والفصلية والشهرية المتعلقة بتغيرات سرعة و اتجاه الرياح ،واالنحراف المعياري ،و توزيع نسبة التكرار لسرعة الرياح واتجاهها واستمرارية اتجاهها لمواقع مختارة 3و ،7وذلك باستخدام بيانات الرياح المسجلة في كل الدقيقة لمدة سنة ( )2102بارتفاع 01م في منطقة مطار السليمانية الدولي الواقع غرب مدينة السليمانية ،في الشمال الشرقي من العراق .بناء على هذه البيانات ،تبين أن الحد األدنى و األقصى لمعدل سرعة الرياح الشهرية للموقعين 3و 7كان في شهر كانون الثاني وحزيران على التوالي ،في حين أن الحد األدنى و األقصى لمعدل سرعة الرياح الفصلية كان في فصلي الشتاء والصيف على التوالي .كما كانت اقصى نسبة تكرارات لسرعة الرياح (≥ 4,1م/ثا) في السنة المذكورة ولمعظم الفصول لنفس الموقعين المذكورين .كما تبين أن محصالت اتجاه الرياح الشهرية والفصلية ذات استمرارية أقصى في اب وموسم الصيف لنفس الموقعين المذكورين. باستخدام برنامج ( )WRPLOT Viewلتحليل اتجاه الرياح ،وتبين أن اتجاه الرياح الفصلية السائدة لكال الموقعين 3و 7في منطقة الدراسة هو الغرب-الشمال الغربي ،في حين اتجاه الرياح السنوية السائدة كان بين الشمال -الشمال الغربي والغرب -الشمال الغربي للموقع 3والغرب -الشمال الغربي للموقع .7أظهر تحليل وردة الرياح للموقعين المذكورين ان متجه محصلة اتجاه الرياح ذو ديمومة إلى حد ما بين 272و 361درجة والذي هو عادة من الغرب إلى الشمال سنويا والفصليا وغالب الشهور .كما قدرت القيم السنوية و الفصلية و الشهرية و اليومية ألس قص الرياح ( )αباستخدام طريقتين مختلفتين بناء على سرعة الرياح المسجلة في دقيقة واحدة في الموقع 21( 0م) وموقع 01( 2م) ،كما تم اختبار الصحة على أساس المعدل الساعي ،وذلك باستخدام القيمة الشهرية ل الفا αالمقدرة لحساب قيم قص الرياح العمودي الشهرية عن طريق استقراء (باستخدام معادلة )Power-lawسرعة الرياح المسجلة في 21مترا فوق مستوى سطح األرض إلى 011متر باالضافة الى ما سبقه فقد تم تقدير قيم شدة قص الرياح األفقية.
تحليل الرياح وتقدير اس قص الرياح لمنطقة مطار السليمانية الدولي
رسالة مقدمة الى مجلس فاكلتي العلوم و تربية العلوم سكول العلوم في جامعة السليمانية كجزء من متطلبات نيل شهادة ماجستير علوم في الفيزياء
من قبل
ئاسو عثمان عبدهللا بكالوريوس فيزياء ) ،(2008جامعة صالح الدين -اربيل باشراف
د .صالح الدين عبدالقادر احمد استاذ مساعد
June / 2014
Sha'aban / 1435
ثوختة لةم تويَذينةوةيةدا تايبةمتةنديةكانى ساآلنة و وةرزى و مانطانةى با شيكراوةتةوة كة ثةيوةستة بة طؤرِانكاريية كانى خيَرايى و ئارِاستةى با و دابةش بوونى ِريَذةى دوبارةبونةوةى خيَراييةكةى بؤ هةردوو سايتى هةلَبذيَردراوى 3و ،7ئةمةش بة بةكارهيَنانى داتاى تؤماركراوى با بؤ هةر دةقيقةيةك بة بةرزى 51م لة ماوةى سالَى 2152لة روبةرى فرِؤكةخانةى نيَودةولَةتى سليَمانى كة كةوتؤتة رِؤذئاواى شارى سليَمانيةوة ،لة باكورى رِؤذهةآلتى عرياق .لةسةر بنةماى ئةو داتايانة ،دةركةوتوة كة بؤ هةردوو سايتى 3و 7نزمرتين و بةرزترينى تيَكرِاى خيَرايى باى مانطانة لة كانونى دووةم و حوزةيرانة بة دواى يةكدا ،لة كاتيَكدا نزمرتين و بةرزترينى تيَكرِاى خيَرايى باى وةرزى لة زستان و هاوينداية وة وةرزةكان و ساآلنة بةرزترين رِيَذةى دوبارةبونةوةى هةية لة خيَرايى با ( ≥ 4,1م/ضركة) .هةروةها دةركةوتوة كة بؤ هةردوو سايتى 3و 7 بةرئةجنامى ئارِاستةى باى مانطانة و وةرزى بةرزترين بةردةوامى هةية لة مانطى ئاب و وةرزى هاويندا. بةرنامةى ) (WRPLOT Viewبةكارهيَنراوة بؤ شيكردنةوةى ئارِاستةى با ،دةركةوتوة كة بؤ هةردوو سايتى 3 و 7ئارِاستةى باى باوى(سائد) وةرزى لة شويَنى ليَكؤلينةوةكة لة رِؤذئاوا -باكورى رِؤذئاواية ،لة كاتيَكدا ئارِاستةى باى باوى ساآلنة لة نيَوان باكور -باكورىرِؤذئاوا و رِؤذئاوا -باكورى رِؤذئاواية بؤ سايتى 3و رِؤذئاوا - باكورى رِؤذئاوا بؤ سايتى .7شيكردنةوةى طولَى با ثيشانى دةدات كة بؤ هةردوو سايتى 3و 7بةرئةجنامى ئارِاستةكراوى ئارِاستةى با بؤ ساآلنة و وةرزى و زؤربةى مانطةكان بةشيَوةيةكى بةرفراوان لة نيَوان 272و 301ثلةداية ئةمةش بة طشتى لة رِؤذئاواوة بؤ باكورة .هةروةها نرخةكانى ساالَنة ،وةرزى ،مانطانة و رِؤذانةى توانى برِينى با ( )αدوزراوةتةوة بة بةكارهيَنانى دوو ِريَطةى جياواز لة سةر بنةماى خيَرايى باى تؤماركراو بؤ هةر دةقيقةيةك لة سايتى 21( 5م) و 51( 2م) ،ثاشان ضاككراوة لةسةر بنةماى تيَكرِاى ( )5يةك سةعات، نرخى خةملَيَنراوى مانطانةى ( αتوانى برِينى با) بةكارهيَنراوة بؤ حسابكردنى برِينى باى ستونى (شاولَى) مانطانة بة بةرزكردنةوةى نرخى خيَرايى با كة تؤماركراوة لة 02م لةسةر ئاستى رِوى زةوى بؤ 022م (بة بةكارهيَنانى ياساى توان) ،هةروةها نرخةكانى توندى برِينى باى ئاسؤيى دوزراوةتةوة.
شيكردنةوةى با و خةمآلندني توانى برِينى با بؤ رِووبةرى فرِؤكةخانةى نيَودةولَةتى سليَمانى نامةيةكة ثيَشكةش كراوة بة ئةجنومةنى فاكلَتى زانست و ثةروةردة زانستةكان سكولَى زانست لة زانكؤى سليَمانى وةك بةشيَك لة ثيَداويستيةكانى بة دةستهيَنانى بروانامةى ماستةرى زانست لة فيزيا لة اليةن
ئاسو عثمان عبداهلل بكالوريؤس لة فيزيا ) ،(2008زانكؤى صالح الدين -هةوليَر
بة سةرثةرشتى
د .صالح الدين عبدالقادر أمحد ثرِؤفيسؤرى ياريدةدةر
June /2014
Pûşper /2714
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