JNTU II B.Tech I Semester Supplimentary Examinations, November 2008
Fluid mechanics and hydraulic machinery
(Electrical & Electronic Engineering)
1. (a) Why does the viscosity of a gas increases with the increasing temperature while that of liquid decreases with increasing temperature.
(b) Glycerin has a density of 1260 Kg/m3 and kinematic viscosity of 0.00183 m2/sec. What shear stress is required to deform this fluid at a strain rate of 104sec?1?
(c) A thin plate is placed between two flat surfaces ‘h’ cm a part such that the vis cosity of liquids on the top and bottom of the plate are ?1 and ?2 respectively. Determine the position of the thin plate such that the viscous resistance to uniform motion of the thin plate is minimum. Assume ?h? to be very small.
2. (a) What do you mean by turbulence ?
(b) What do you mean by one, two, three dimensional flow?
(c) Derive the continuity equation for one dimensional fluid flow.
3. (a) Derive the Darcy-weisbach equation for friction head loss in a pipe.
(b) Water is flowing through a horizontal pipe line 1500m long and 200mm in diameter. Pressures at the two ends of the pope line are respectively 12Kpa and 2Kpa. If f = 0.015, determine the discharge through the pipe in litres per minute. Consider only frictional loss.
4. (a) Derive the expressions for force and work done per second by the jet when it strikes a curved plate moving in the direction of the jet.
(b) A jet of water 20cm in diameter and moving with a velocity of 20m/sec impinges normally on a series of flat vanes mounted on the periphery of a wheel. If the velocity of the vanes is 8m/sec, determine
i. the force exerted by the jet on the wheel
ii. work done by the jet on the wheel per second and
iii. hydraulic efficiency.
5. (a) What are the elements of hydro electric power plants? Describe about water ways and penstocks with neat sketches if necessary.
(b) The catchment area at a proposed site for a hydropower plant is 200 Km2 and possible head of water is 140 m. The average annual rainfall is 145 cm and the losses are 16%. How much power can be developed?
6. (a) Why is the end of a draft tube immersed below the tail water level. Explain
with a neat sketch. Define draft tube efficiency and derive its equation
(b) A Kaplan turbine has the following details about its draft tube. Find the
pressure at inlet of the draft tube.
Inlet diameter of draft tube = 2m
Out let diameter of draft tube = 3m
Velocity of water at outlet = 4.2 m /sec
Atmosphere pressure = 10.1 m of water
Height of draft tube above tail race = 3.5m
Loss of head in draft tube = 0.2 times the velocity head at outlet.
7. (a) Define unit power and unit speed and derive the equations for the same. What are their uses ?
(b) What is a surge tank and what are the uses of it in a hydropower turbine installation ? Explain where and how it is located with the help of a neat sketch.
8. (a) What equation is employed to find the work done by the impeller of a centrifugal pump. Derive the equation for work done.
(b) What are the equations for work done and discharge of a reciprocating pump?
Define the slip and coefficient of discharge of a reciprocating pump.