## Fluid Mechanics and Hydraulic Machines Practice Questions Set 1

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

Options are :

• Irrotational flow only
• Three-dimensional flow
• Uniform flow
• Two-dimensional flow

##### A stream line is one

Options are :

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

Answer : In which the flow cannot cross the bounding surface

Options are :

• Any of these
• Stable
• Unstable
• Neutral

##### What is the reciprocal of compressibility?

Options are :

• Bulk modulus of elasticity
• Any of the above
• Young's modulus of elasticity
• Shear modulus of elasticity

Answer : Bulk modulus of elasticity

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

Options are :

• Specific weight
• Mass
• Volume
• Weight

##### The momentum convection factor ? is used to account for

Options are :

• Non-uniform distribution of velocities at inlet and outlet sections
• Change in total energy
• Change in direction of flow
• Change in mass rate of flow

Answer : Non-uniform distribution of velocities at inlet and outlet sections

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

Options are :

• Centre of gravity
• Centre of buoyancy
• Metacentre
• None of these

##### A pitot-tube is used to measure

Options are :

• Pressure of flow
• Flow rate
• Velocity of flow
• Total energy

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

Options are :

• Ideal fluids
• Newtonian fluids
• Non-Newtonian fluids
• None of these

##### A floating body is in stable equilibrium when

Options are :

• The metacentre is below its centre of gravity
• The metacentre is above its centre of gravity
• The metacentric height is zero
• Its centre of gravity is below the centre of buoyancy

Answer : The metacentre is above its centre of gravity

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

Options are :

• Pressure and gravity
• Pressure and viscosity
• Viscosity and turbulence
• Pressure and turbulence

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

Options are :

• More than their ambient counterparts
• The same as in ambient flow
• None of these
• Less than their ambient counterparts

Answer : More than their ambient counterparts

##### The critical depth is the depth of flow at which

Options are :

• The unit discharge is minimum
• The specific energy is minimum
• The specific energy is maximum
• The Froude number is less than unity

Answer : The specific energy is minimum

##### How can the separation of boundary prevented?

Options are :

• All of these
• Providing the bypass in the slotted wing
• Suction of the slow moving fluid by a suction slot
• Providing small divergence in a diffuser

##### Loss of head at exit of a pipe is given as

Options are :

• V^(3) /2g
• V/2g
• None of these
• V^(2) /2g

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

Options are :

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

Answer : His pioneering research on flow of low viscosity fluids bringing forward a new concept of boundary layer

##### The pressure drag depends upon

Options are :

• The boundary layer formation
• The shear stresses generated on the body surface
• The separation of boundary layer and the size of the wake
• The characteristics of the oncoming flow

Answer : The separation of boundary layer and the size of the wake

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

Options are :

• Mach number and relative roughness
• Reynolds number and relative roughness
• Froude number and Mach number
• Froude number and relative roughness

Answer : Reynolds number and relative roughness

##### Due to ………… phenomena water hammer is caused

Options are :

• Incompressibility of fluid
• Sudden opening of a valve in a pipeline
• The material of pipe being elastic
• Sudden closure of a valve in pipe flow

Answer : Sudden closure of a valve in pipe flow

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

Options are :

• 1/8th of the total supply head
• 1/4th of the total supply head
• 1/2 of the total supply head
• 1/3rd of the total supply head

##### Aging of pipes implies

Options are :

• None of these
• Increase in absolute roughness linearly with time and hence friction factor
• A decrease in the value of friction factor
• Pipe becoming smoother with time

Answer : Increase in absolute roughness linearly with time and hence friction factor

##### When does a hydraulic jump occur in a channel?

Options are :

• The bed slope is adverse
• Flow changes from sub critical to supercritical
• The bed slope changes from steep to mild
• None of these

Answer : The bed slope changes from steep to mild

##### The friction drag is primarily due to

Options are :

• Shear stresses generated due to viscous action
• Separation of boundary layer
• None of these
• Weight component in the direction of flow

Answer : Shear stresses generated due to viscous action

##### The sonic speed in an ideal gas varies

Options are :

• None of these
• Directly as the absolute pressure
• Inversely as the absolute temperature
• Inversely as bulk modulus

##### The sonic velocity in a fluid medium is directly proportional to

Options are :

• Mach number
• Square root of temperature
• None of these
• Pressure

Answer : Square root of temperature

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

Options are :

• 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
• None of these
• The shape of the object should be so designed that the pressure distribution over its surface is symmetrical
• The object should be symmetrical and the axis of the symmetry be aligned parallel to the flow direction

Answer : 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

##### The Darcy-Weisbach friction factor 'f' which is a direct measure of resistance to flow in pipes depends on

Options are :

• Relative roughness, velocity and viscosity
• Roughness height, diameter and velocity
• Roughness height, diameter, velocity and kinematic viscosity
• Relative roughness, diameter and viscosity

Answer : Roughness height, diameter, velocity and kinematic viscosity

##### When a turbulent flow is considered steady?

Options are :

• The discharge remains constant
• Temporal mean velocity at a point remains constant with time
• The velocity at a point does not change with time
• The algebraic sum of velocity fluctuation is zero

Answer : Temporal mean velocity at a point remains constant with time

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

Options are :

• Parallel to the direction of flow
• Normal to the direction of flow
• None of the above
• Either of the above

Answer : Normal to the direction of flow

##### In dimensional analysis the Buckingham's ?-theorem is widely used and expresses the resulting equation in terms of

Options are :

• The repeating variables
• (n-m) dimensionless parameters
• n dimensionless parameters
• Geometric, kinematic, and dynamic variables

##### 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

Options are :

• Hyperbolic law
• Logarithmic law
• Parabolic law
• Linear law

##### Dimensional analysis is used to

Options are :

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

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

Options are :

• 2A?H1/Cd.a^(2.2g)
• 2A?H1/Cd.a.?2g
• 4A?H1/Cd.a.?2g
• A?H1/Cd.a.?2g

##### What is the most essential feature of a turbulent flow?

Options are :

• Velocity at a point remains constant with time
• Velocity and pressure at a point exhibit irregular fluctuations of high frequency
• Large discharge
• High velocity

Answer : Velocity and pressure at a point exhibit irregular fluctuations of high frequency

Options are :

• 2%
• 1%
• 1.5%
• 2.5%

##### To apply Buckingham's ?-theorem, 'm' repeating variables amongst the 'n' variables influencing the phenomenon are selected such that they

Options are :

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

Answer : In combination contain each of the m fundamental dimensions involved in the problem

##### Intensity of turbulence is

Options are :

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

Answer : The violence of turbulent fluctuations and is measured by the root mean square value of velocity fluctuations

##### Loss of head due to sudden enlargement is given as

Options are :

• (V1^(2) - V2^(2))/2g
• (V1 - V2)^(2)/2g
• (V1^(3) - V2^(3))/2g
• (V1 - V2)^(3)/2g