# Fluid Mechanics and hydraulic machines - Mechanical Engineering test

## Fluid Mechanics and hydraulic machines - Mechanical Engineering test

1) Fluids which do not follow the linear relationship between shear stress and rate of deformation are termed as

a) Ideal fluids
b) Newtonian fluids
c) Non-Newtonian fluids
d) None of these

2) What is the reciprocal of compressibility?

a) Shear modulus of elasticity.
b) Young’s modulus of elasticity.
c) Bulk modulus of elasticity.
d) Any of the above.

ANSWER: c) Bulk modulus of elasticity.

3) The point of application of the force of buoyancy on the body is known as

a) Metacentre.
b) Centre of buoyancy.
c) Centre of gravity.
d) None of these.

4) A floating body is in stable equilibrium when

a) The metacentric height is zero.
b) Its centre of gravity is below the centre of buoyancy.
c) The metacentre is above its centre of gravity.
d) The metacentre is below its centre of gravity.

ANSWER: c) The metacentre is above its centre of gravity.

5) Equilibrium is called …………… if a body does not return to its original position from the slightly displaced angular position and heels farther away, when given a small angular displacement.

a) Unstable.
b) Stable.
c) Neutral.
d) Any of these.

6) A stream line is one

a) In which stream function does not change.
b) Which has a constant area throughout its length so that the velocity remains constant.
c) In which the flow cannot cross the bounding surface.
d) None of these.

ANSWER: c) In which the flow cannot cross the bounding surface.

7) The concept of stream function which is based on the principle of continuity is applicable to

a) Three-dimensional flow.
b) Two-dimensional flow.
c) Irrotational flow only.
d) Uniform flow.

8) Bernoulli’s equation of the form (p/w + v2/2g + z = constant) represents total energy per unit

a) Mass
b) Weight
c) Volume
d) Specific weight

9) A pitot-tube is used to measure

a) Flow rate.
b) Pressure of flow.
c) Velocity of flow.
d) Total energy.

10) The momentum convection factor β is used to account for

a) Non-uniform distribution of velocities at inlet and outlet sections.
b) Change in total energy.
c) Change in mass rate of flow.
d) Change in direction of flow.

ANSWER: a) Non-uniform distribution of velocities at inlet and outlet sections.

11) Dimensional analysis is used to

a) Derive rational formulae for a flow phenomenon.
b) Derive equations expressed in terms of non-dimensional parameters to show the relative significance of each parameter.
c) Test the dimensional homogeneity of any equation of fluid motion.
d) All of these.

12) In dimensional analysis the Buckingham’s π-theorem is widely used and expresses the resulting equation in terms of

a) Geometric, kinematic, and dynamic variables.
b) The repeating variables.
c) (n-m) dimensionless parameters.
d) n dimensionless parameters.

13) To apply Buckingham’s π-theorem, ‘m’ repeating variables amongst the ‘n’ variables influencing the phenomenon are selected such that they

a) Must always contain the dependent variables
b) In combination contain each of the m fundamental dimensions involved in the problem
c) Belong to kinematic and dynamic category of variables
d) None of these

ANSWER: b) In combination contain each of the m fundamental dimensions involved in the problem

14) How much time is required to empty a tank through an orifice at its bottom?

a) 2A√H1/Cd.a2.2g
b) 2A√H1/Cd.a.√2g
c) A√H1/Cd.a.√2g
d) 4A√H1/Cd.a.√2g

15) An error of 1% measuring H will produce …………..error in discharge over a rectangular notch or weir.

a) 1%
b) 1.5%
c) 2%
d) 2.5%

16) The pressure gradient in the direction of flow is equal to the shear gradient in the direction

a) Parallel to the direction of flow.
b) Normal to the direction of flow.
c) Either of the above.
d) None of the above.

ANSWER: b) Normal to the direction of flow.

17) What is the most essential feature of a turbulent flow?

a) Large discharge.
b) Velocity and pressure at a point exhibit irregular fluctuations of high frequency.
c) High velocity.
d) Velocity at a point remains constant with time.

ANSWER: b) Velocity and pressure at a point exhibit irregular fluctuations of high frequency.

18) In turbulent flow the velocity distribution is a function of the distance y measured from the boundary surface and shear friction velocity Up and follows a

a) Parabolic law.
b) Hyperbolic law.
c) Linear law.
d) Logarithmic law.

19) When a turbulent flow is considered steady?

a) Temporal mean velocity at a point remains constant with time.
b) The velocity at a point does not change with time.
c) The algebraic sum of velocity fluctuation is zero.
d) The discharge remains constant.

ANSWER: a) Temporal mean velocity at a point remains constant with time.

20) The Darcy-Weisbach friction factor ‘f’ which is a direct measure of resistance to flow in pipes depends on

a) Relative roughness, velocity and viscosity.
b) Relative roughness, diameter and viscosity.
c) Roughness height, diameter and velocity.
d) Roughness height, diameter, velocity and kinematic viscosity.

ANSWER: d) Roughness height, diameter, velocity and kinematic viscosity.

21) Intensity of turbulence is

a) The mean time interval between the reversals in the sign of velocity fluctuation.
b) The violence of turbulent fluctuations and is measured by the root mean square value of velocity fluctuations.
c) The average K.E. of turbulence.
d) None of these.

ANSWER: b) The violence of turbulent fluctuations and is measured by the root mean square value of velocity fluctuations.

22) …………………….determine the friction factor for turbulent flow in a rough pipe.

a) Reynolds number and relative roughness.
b) Froude number and Mach number.
c) Mach number and relative roughness.
d) Froude number and relative roughness.

ANSWER: a) Reynolds number and relative roughness.

23) Loss of head due to sudden enlargement is given as

a) (V1 - V2)3/2g
b) (V1 - V2)2/2g
c) (V12 - V22)/2g
d) (V13 - V23)/2g

24) Loss of head at exit of a pipe is given as

a) V2 /2g
b) V3 /2g
c) V/2g
d) None of these

25) At what value of head lost due to friction in pipe, will the power transmitted through the pipe be maximum?

a) 1/2 of the total supply head
b) 1/3rd of the total supply head
c) 1/4th of the total supply head
d) 1/8th of the total supply head

26) Due to ………… phenomena water hammer is caused.

a) Sudden opening of a valve in a pipeline.
b) The material of pipe being elastic.
c) Incompressibility of fluid.
d) Sudden closure of a valve in pipe flow.

ANSWER: d) Sudden closure of a valve in pipe flow.

27) Prandtl is regarded as the father of modern fluid mechanics on account of

a) His new interpretations on fluid resistance.
b) His fundamental research in the field of aircraft engineering.
c) His pioneering research on flow of low viscosity fluids bringing forward a new concept of boundary layer.
d) None of these.

ANSWER: c) His pioneering research on flow of low viscosity fluids bringing forward a new concept of boundary layer.

28) How can the separation of boundary prevented?

a) Providing the bypass in the slotted wing.
b) Providing small divergence in a diffuser.
c) Suction of the slow moving fluid by a suction slot
d) All of these.

29) Aging of pipes implies

a) Increase in absolute roughness linearly with time and hence friction factor.
b) A decrease in the value of friction factor.
c) Pipe becoming smoother with time.
d) None of these.

ANSWER: a) Increase in absolute roughness linearly with time and hence friction factor.

30) The pressure drag depends upon

a) The separation of boundary layer and the size of the wake.
b) The shear stresses generated on the body surface.
c) The boundary layer formation.
d) The characteristics of the oncoming flow.

ANSWER: a) The separation of boundary layer and the size of the wake.

31) The friction drag is primarily due to

a) Weight component in the direction of flow.
b) Shear stresses generated due to viscous action.
c) Separation of boundary layer.
d) None of these.

ANSWER: b) Shear stresses generated due to viscous action.

32) The drag and lift forces experienced by an object placed in a fluid stream are due to

a) Pressure and gravity.
b) Pressure and turbulence.
c) Pressure and viscosity.
d) Viscosity and turbulence.

33) Which of the following conditions / requirements is necessary to induce lift on an object?

a) The object should be so shaped that there are zones of high and low velocities resulting in pressure difference between upper side and bottom side of the object.
b) The object should be symmetrical and the axis of the symmetry be aligned parallel to the flow direction.
c) The shape of the object should be so designed that the pressure distribution over its surface is symmetrical.
d) None of these.

ANSWER: a) The object should be so shaped that there are zones of high and low velocities resulting in pressure difference between upper side and bottom side of the object.

34) The sonic velocity in a fluid medium is directly proportional to

a) Mach number.
b) Square root of temperature.
c) Pressure.
d) None of these.

ANSWER: b) Square root of temperature.

35) The stagnation pressure (Ps) and temperature (Ts) are

a) The same as in ambient flow.
b) Less than their ambient counterparts.
c) More than their ambient counterparts.
d) None of these.

ANSWER: c) More than their ambient counterparts.

36) The sonic speed in an ideal gas varies

a) Directly as the absolute pressure.
b) Inversely as the absolute temperature.
c) Inversely as bulk modulus.
d) None of these.

37) The critical depth is the depth of flow at which

a) The specific energy is minimum.
b) The unit discharge is minimum.
c) The specific energy is maximum.
d) The Froude number is less than unity.

ANSWER: a) The specific energy is minimum.

38) When does a hydraulic jump occur in a channel?

a) The bed slope changes from steep to mild.
b) The bed slope is adverse.
c) Flow changes from sub critical to supercritical.
d) None of these.