JE – 893

*JE893*

III Semester B.E. (Civil) Degree Examination, June/July 2013 (2K11 Scheme) CE 304 : FLUID MECHANICS AND HYDRAULIC MACHINERY Time : 3 Hours

Max. Marks : 100

Instructions : 1) Part A is compulsory. 2) Answer any five full questions from the Part B and Part C selecting at least one from each Part. 3) Any missing data may be assumed suitably and state them. PART – A 1. a) Define fluid mechanics and state ideal and real fluids. b) What is viscosity ? State Newton’s law of viscosity. c) Define terms : Absolute pressure, gauge pressure and vacuum pressure. d) Define terms : Total pressure and centre of pressure. e) Define fluid kinematics. f) Distinguish between Langrangian and Eulerian method of fluid flow analysis. g) Define stream line and stream tube. h) What is the basic difference between a turbine and a pump ? i) Define hydraulic gradient line and total energy gradient line. j) Define Froude’s and Reynold’s number.

(2×10=20)

PART – B 2. a) State and prove Pascal’s law.

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b) Derive general equation of fluid statics of the form p = rh, with usual notations.

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c) The space between two parallel plates kept 4 mm apart is filled with an oil of dynamic viscosity 0.2 pa.s. What is the shear stress on the lower fixed plate, if the upper one is moved with a velocity of 1.5 m/s ?

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P.T.O.

JE – 893

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*JE893*

3. a) An inverted U-tube manometer is connected to two pressure points in a horizontal water pipe. The space above the water in the two limbs of manometer is filled with oil of specific gravity 0.88. The difference of level of water column in the two limbs is 400 mm. Determine the pressure difference between these two points and express in N/m2.

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b) Assuming the interstices in a clay are if size equal to one tenth the mean diameter of the grain, estimate the height to which water will rise in a clay soil of average grain diameter 0.05 mm. Assume surface tension at air-water interface as 0.073 m/s.

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c) Distinguish between simple and differential type of manometers with figures.

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4. a) A pipe line 4 m in diameter contains a gate valve. The pressure at the centre of the pipe is 200 kN/m2. The pipe is filled with an oil of specific gravity 0.91. What will be the force exerted by the oil upon the gate ? Also locate the position of the centre of pressure.

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b) Derive continuity equation for a 3-dimensional flow in the differential form. Clearly indicate each terms and explain how it is modified under different cases.

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PART – C 5. a) State and prove Bernoulli’s equation from first principles. Also mention the assumptions made.

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b) A vertical pipe line carries oil of specific gravity 0.85. A 400 × 160 mm venturimeter is provided in the pipe line and difference in the elevation of the throat section and the entrance section of this venturimeter is 500 mm. The gauge deflection of the u-tube mercury manometer connected to the venturimeter is 300 mm. Assuming the coefficient of the water as 0.98. Determine the discharge of the oil through the pipe and the pressure difference between the entrance and the throat sections.

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6. a) What are hydraulic co-efficients of orifice ? Explain briefly, how do you determine these co-efficients experimentally ?

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b) A tank has two identical orifice in one of its vertical sides located at 2 m and 4 m below the water surface. Find the point at which the two jets intersect assuming a co-efficient of velocity 0.97 for both orifices.

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*JE893*

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JE – 893

7. a) A rectangular weir of crest length 600 mm is used to measure the flow of water in a rectangular channel 600 mm wide and 500 mm deep. The water level in the weir is 60 mm above the crest of weir. Find the discharge in the channel taking into account of velocity of approach also. Take Cd = 0.62. b) Define a Cippoletti notch/weir. What is the discharge over such a weir ? Explain with neat diagram and derive mathematical relationship. 8. a) Derive expression for the force exerted by a jet on moving flat plate (a) normal to the jet. (b) inclined to the jet. Also, find the expression for the work done. b) Classify the turbines on the basis of i) Hydraulic action of water ii) Direction of flow of water in the runner iii) Specific speed of turbines. 9. a) List the comparison of centrifugal and reciprocating pumps.

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b) What do you mean by dimensional analysis ? In what way does it help in generalising a problem ?

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c) What is meant by similitude ? Describe its types.

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