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

Answer : Two-dimensional flow

Heat Transfer Practice Questions (Mechanical Engineering) Set 1

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

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


Options are :

  • Any of these
  • Stable
  • Unstable
  • Neutral

Answer : Unstable

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

Engineering Mechanics Practice Questions (Mechanical) Set 1

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


Options are :

  • Specific weight
  • Mass
  • Volume
  • Weight

Answer : 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

Answer : Centre of buoyancy

A pitot-tube is used to measure


Options are :

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

Answer : Velocity of flow

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

Answer : Non-Newtonian fluids

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

Answer : Pressure and viscosity

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

Answer : All of these

Loss of head at exit of a pipe is given as


Options are :

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

Answer : 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

Answer : 1/4th 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

Answer : None of these

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

Answer : (n-m) dimensionless parameters

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

Answer : Logarithmic 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

Answer : All of these

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

Answer : 2A?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

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


Options are :

  • 2%
  • 1%
  • 1.5%
  • 2.5%

Answer : 1.5%

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

Answer : (V1 - V2)^(2)/2g

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