The lower limit of the critical Reynolds number below which all disturbances in pipe flow are damped out by viscous action has a value approximately equal to
(1) 1 (2) 500 (3) 1000 (4) 2000

Ans: (4)

. The most essential feature of a turbulent flow is
(1) large discharge
(2) High velocity
(3) velocity and pressure at a point exhibit irregular fluctuations of high frequency
(4) velocity at a point remains constant with time

Ans: (3)

09. The velocity distribution in turbulent flow follows a
(1) parabolic law (2) logarithmic law (3) linear law (4) hyperbolic law
Ans: (2)

10. Steel and cast iron pipes carrying fluid under pressure are regarded as hydraulically smooth when
(1) the boundary surfaceis relatively smooth
(2) the roughness projections are of low height
(3) the roughness elements are completely covered by the laminar sub-layer
(4) the laminar layer is thin as comparedto the average heightof roughness elements

Ans: (3)

11. The Darcy – Weisbach friction factor ‘f’ which is a direct measure ofresistance to flow in pipes is dependant on

(1) roughness height, diameter and velocity
(2) relative roughness, diameter and viscosity
(3) relative roughness, velocity and viscosity
(4) relative height, diameter, velocity and kinematic viscosity
Ans: (4)

The parameters which determine the friction factor for turbulent flow in a rough pipe are

(1) Froude number and relative roughness
(2) Froude number and Mach number
(3) Reynolds number and relative roughness
(4) Mach number and relative roughness
Ans: (3)

13. In case of turbulent flow of a fluid through a circular tube, as compared to the case of laminar flow, at the same flow, rate, the maximum velocityis __________, shear stress at the wall is __________, and the pressure drop across a given length is________.

(1) higher, higher, higher (2) higher, lower, lower
(3) lower, higher, higher (3) lower, higher, lower
Ans: (3)

14. The hydraulic efficiency of an impulse turbine is maximum, when the velocity of wheel is ______ that of the jet velocity.
(1) one-fourth (2) one-half (3) three-fourth (4) double
Ans: (2)

16. In a reaction turbine, the draft tube is used
(1) to run the turbine full (2) to prevent air to enter the turbine
(3) to increase the effective head of water (4) to transport water to downstream
Ans: (3)

17. In an inward flow reaction turbine
(1) the water flows parallelto the axis of the wheel
(2) the water enters at the centre of the wheel and from there flows towards the outer periphery of the wheel
(3) the water enters the wheel at outer periphery, and then flows towards the centre of the wheel
(4) the flow of water is partly radial and partly axial
Ans: (3)


18. In a Kaplan turbine runner, the number of blades are generally
(1) 2 to 4 (2) 4 to 8 (3) 8 to 16 (4) 16 to 24
Ans: (2)


21. The turbine to be used for 450 m head of water is
(1) Pelton wheel (2) Francis turbine (3) Kaplan turbine (4) None of these
Ans: (1)

22. The cavitation in a hydraulic machine
(1) causes noise and vibration of various parts (2) makes the surface rough
(3) reduces the discharge of a turbine (4) causes sudden drop in power output and efficiency
Ans: (1)

23. The specific speed of a turbine is speed of an imaginary turbine, identical with the given turbine, which
(1) delivers unit discharge under unit load
(2) delivers unit discharge under unit speed
(3) develops unit H.P. under unit head
(4) develops unit H.P. under unit speed
Ans: (3)

24. In a centrifugal pump the liquid enters the pump
(1) at the centre (2) at the top (3) at the bottom (4) from sides Ans: (1)

25. Multistage centrifugal pumps are used to
(1) give high discharge (2) pump viscous fluids
(3) produce high heads (4) None of these
Ans: (3)