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Code No: R5220303 R5II B.Tech II Semester(R05) Supplementary Examinations, December 2010

MECHANICS OF FLUIDS(Mechanical Engineering)

Time: 3 hours Max Marks: 80Answer any FIVE Questions

All Questions carry equal marks

1. (a) For measuring small pressure differences, explain with sketches how an inclined U-tube manometeris used.

(b) Explain three conditions of equilibrium of a floating body. [8+8]

2. A two-dimensional flow field is given by = 3xy, determine:

(a) The stream function

(b) The velocity at L(2,6) and M (6,6) and the pressure difference between the points L and M.

(c) The discharge between the streamlines passing through the points L and M. [16]

3. An open circuit wind tunnel draws air from the atmosphere through a well contoured nozzle. In thetest section, where the flow is straight and nearly uniform, a static pressure tap is drilled into thetunnel wall. A manometer connected to the tap shows that the wall pressure within the tunnel is45 mm of water below atmospheric. Assume that air is incompressible and at 250 C, pressure is 100Kpa(absolute). Calculate the velocity in the wind tunnel section. Density of water is 999kg/m3 andcharacteristic gas constant for air is 287 J/Kg K. [16]

4. (a) Derive an expression for discharge as liquids through a rectangular notch.

(b) A 120mm 60mm venturimeter with Cd = 0.98 is to be replaced by an orifice meter having

a value of Cd

= 0.6, is both the meters are to give the same differential mercury monometerreading for a discharge of 100 lit/sec and the inlet diameter to remain 125 mm. what should bethe diameter of orifice. [7+9]

5. (a) Explain with a neat sketch the boundary layer characteristics when a fluid is flowing over a flatplate.

(b) A thin flat plate 0.3 m wide and 0.6 m long is suspended and exposed parallel to air flowingwith a velocity of 3 m/sec. Calculate drag force on both sides of the plate when the 0.3 m edgeis oriented parallel to free stream. Consider flow to be laminar and assume for air kinematicviscosity is 0.18 stokes and density is 1.2 kg/m3. [10+6]

6. (a) Derive Darcy-Weisbach equation for loss of head in a pipe.

(b) Two tanks are connected by a 300 mm diameter 1000 m long pipe. Find the rate of flow if thedifference of water level in the tank is 10 m. Take 4f = 0.04 and ignore minor losses. [10+6]

7. A Flow of 420 liters/min of oil of specific gravity 0.91 and viscosity 1.24 poise is pumped through apipeline 75mm diameter having a length of 62m and whose outlet is 3m higher than its inlet. Estimatethe power required for the pump if its efficiency is 60%. [16]

8. (a) what is the relation between pressure and density of a compressible fluid for?

i. Isothermal process

ii. Adiabatic process.

(b) A gas is flowing through a horizontal pipe at a temperature of 40C. The diameter of the pipeis 8cm and at a section I in the pipe, the pressure is 30.3N/cm2 (gauge). The diameter of the

pipe changes from 8cm to 4cm at the section II, where pressure is 20.3N/cm2

(gauge). Find thevelocities of the gas at these sections assuming an isothermal process. Take R=287.14Nm/Kg.Kand atmosphere pressure=10N/ cm2. [6+10]

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