Category: Fluid Mechanics Objective Questions

250+ TOP MCQs on Geometrical Properties of Triangular Section – 2 and Answers

Advanced Fluid Mechanics Questions and Answers on “Geometrical Properties of Triangular Section – 2”.

1. Determine the Hydraulic depth for a triangular channel having side slope of 1H:3V and depth 15m.
a) 30m
b) 15m
c) 7.5m
d) 3.75m
Answer: c
Clarification: Hydraulic Depth = y/2
= 15/2
= 7.5m.

2. Calculate the Hydraulic Radius for a triangular channel having side slope 2H:4V and a depth of 3m.
a) 0.68m
b) 0.67m
c) 0.66m
d) 0.65m
Answer: b
Clarification:
advanced-fluid-mechanics-questions-answers-q2

3. The Hydraulic Depth of a triangular channel is 5m, calculate the normal depth of the channel.
a) 8m
b) 10m
c) 12m
d) 14m
Answer: b
Clarification: D = y/2
y = 2D = 10m.

4. The hydraulic radius of a triangular section is 0.45m and the normal depth of the channel is 2m, calculate the side slope of the channel.
a) 1/4
b) 1/3
c) 1/2
d) 1
Answer: c
Clarification:
advanced-fluid-mechanics-questions-answers-q4

5. The ratio between hydraulic radius and hydraulic depth of a triangular channel is 31/100, calculate the side slope of the channel.
a) 1⁄2
b) 1⁄3
c) 1⁄4
d) 2⁄3
Answer: b
Clarification:
advanced-fluid-mechanics-questions-answers-q5

6. Calculate the wetted perimeter of a triangular channel section having a depth of 5m and the side slope is equal to tan⁡ 30°.
a) 9.54m
b) 10.54m
c) 11.54m
d) 12.54m
Answer: c
Clarification:
advanced-fluid-mechanics-questions-answers-q6

7. The discharge of water through a triangular section is 90m3⁄s and velocity of flow is 5 m⁄s. Calculate the hydraulic depth of the channel having a side slope 1⁄2.
a) 2m
b) 3m
c) 4m
d) 5m
Answer: b
Clarification:
advanced-fluid-mechanics-questions-answers-q7

8. The top width of a triangular channel section is 4m and the depth of the section is 8m, calculate the wetted perimeter of the channel.
a) 16.5m
b) 17.5m
c) 18.5m
d) 19.5m
Answer: a
Clarification:
advanced-fluid-mechanics-questions-answers-q8

9. In the given figure the vertical angle is 60°, calculate the wetted area of the channel.
advanced-fluid-mechanics-questions-answers-q9
a) 23.3m2
b) 33.3m2
c) 43.3m2
d) 53.3m2
Answer: c
Clarification: Area = (5 tan⁡60°)(5)
Area = 43.3m2.

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250+ TOP MCQs on Viscosity – 1 and Answers

Fluid Mechanics Multiple Choice Questions on “Viscosity – 1”.

1. Water flows between two plates of which the upper one is stationary and the lower one is moving with a velocity V. What will be the velocity of the fluid in contact with the upper plate?
a) V
b) N ⁄ 2
c) 2V
d) 0

Answer: d
Clarification: According to the No-Slip condition, the relative velocity between the plate and the fluid in contact with it must be zero. Thus, the velocity of the fluid in contact with the upper plate is 0 and that with the lower plate is V.

2. The viscous force the relative motion between the adjacent layers of a fluid in motion.
Which one of the flowing fits best in the sentence?
a) opposes
b) never affects
c) facilitates
d) may effect under certain conditions

Answer: a
Clarification: Viscosity is the internal friction of a fluid in motion. It is the property by the virtue of which the relative motion between two adjacent fluid layers is opposed.

3. The viscosity of a fluid in motion is 1 Poise. What will be it’s viscosity (in Poise) when the fluid is at rest?
a) 0
b) 0.5
c) 1
d) 2

Answer: c
Clarification: Viscosity is the property of a fluid and is constant for a given fluid under given conditions, irrespective of the fact whether the fluid is at rest or in motion.

4. Which of the following correctly states how the viscosities of a liquid and a gas will change with temperature?
a) Viscosity increases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas
b) Viscosity increases with the increase in temperature of a liquid and increases with the increase in temperature of a gas
c) Viscosity decreases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas
d) Viscosity decreases with the increase in temperature of a liquid and increases with the increase in temperature of a gas

Answer: a
Clarification: Viscosity of a liquid is due to the cohesion between it’s molecules. With the increase in temperature of a liquid, cohesion increases, leading to the rise in viscosity. Viscosity of a gas is due to the momentum transfer between it’s molecules. With the increase in the temperature of a liquid, molecular motion increases, leading to the fall in viscosity.

5. Which one of the following is not a unit of dynamic viscosity?
a) Pa-s
b) N-s/m2
c) Poise
d) Stokes

Answer: d
Clarification:
where F= viscous force, A= area, du ⁄ dx = velocity gradient, μ = co-effcient of viscosity. Therefore,

SI unit of μ is N-s/m2 = Pa-s and CGS unit of μ is dyne-s/cm2. 1 Poise= 1 dyne-s/cm2 and 1 Stokes= 1 cm2/s. Thus, Stokes is not an unit of μ, rather it is a unit of kinematic viscosity υ.

6. Which of the following is a unit of dynamic viscosity?
a) [M1 L1 T-1].
b) [M1 L-1 T-1].
c) [M1 L-2 T-2].
d) [M1 L-2 T-2].

Answer: b

7. Which one of the following is the CGS unit of dynamic viscosity?
a) Stokes
b) Pa-s
c) m2/s
d) Poise

Answer: d

8. The dynamic viscosity of a fluid is 1 Poise. What should one multiply to it to get the answer in N-s/m2?
a) 0.1
b) 1
c) 10
d) 100

Answer: a

9. Which of the following is a unit of kinematic viscosity?
a) Stokes
b) Pa-s
c) m2=s
d) Poise

Answer: a
Clarification: ν = μ/ρ, where ν = kinematic viscosity, μ = dynamic viscosity and ρ = density of the fluid. Unit of μ is dyne-s/cm2 and that of ρ is kg/cm3.
Thus, the unit of ν is cm2/s = Stokes Poise is the unit of dynamic viscosity.
1 Poise = 1 dyne-s/cm2

10. Which of the following is the dimension of kinematic viscosity?
a) [L1 T-1].
b) [L1 T-2].
c) [L2 T-1].
d) [L2 T-2].

Answer: c

11. The kinematic viscosity of a fluid is 0.1 Stokes. What will be the value is m2/s?
a) 10-2
b) 10-3
c) 10-4
d) 10-5

Answer: d
Clarification: 1Stokes = 1cm2/s = 10-4m2/s Therefore, 0.1Stokes = 10-1cm2/s = 10-5m2/s.

12. The shear stress at a point in a liquid is found to be 0.03 N/m2. The velocity gradient at the point is 0.15 s-1. What will be it’s viscosity (in Poise)?
a) 20
b) 2
c) 0.2
d) 0.5

Answer: b

250+ TOP MCQs on Pressure Distribution in a Liquid and Answers

Fluid Mechanics MCQs on “Pressure Distribution in a Liquid Subjected to Horizontal / Vertical Acceleration”.

1. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 3.6 m/s2. If tank is open at the top then calculate the angle of water surface to the horizontal.
a) 20.15
b) 69.84
c) 40.30
d) None of the mentioned

Answer: a
Clarification: tanθ=a/g
tanθ=3.6/9.8
θ=20.15⁰.

2. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 4.8 m/s2. The length of tank is 7 m and depth is 1.5 m. If tank is open at the top then calculate the maximum pressure intensity at the bottom.
a) 6.3 N/cm2
b) 3.15 N/cm2
c) 12.6 N/cm2
d) 1.6 N/cm2

Answer: b
Clarification: tanθ=a/g
tanθ=4.8/9.8
θ=26.07⁰
h= d+(L/2)tanθ
= 1.5+3.5tan26.07
= 3.21 m
p=ρ*g*h
=3.15 N/cm2.

3. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 5.5 m/s2. The length of tank is 5.5 m and depth is 2 m. If tank is open at the top then calculate the minimum pressure intensity at the bottom.
a) 3.8 N/cm2
b) 1.9 N/cm2
c) 5.7 N/cm2
d) 2.6 N/cm2

Answer: b
Clarification: tanθ=a/g
tanθ=5.5/9.8
θ=29.28⁰
h= d-(L/2)tanθ
= 2-2.75 tan29.28
= 3.21 m

p=ρ*g*h
=1.9 N/cm2.

4. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 4.5 m/s2.The length, width and depth of tank are 7 m, 3m, 2.5m respectively. If tank is open at the top then calculate the total force due to water acting on higher pressure end of the tank.
a) 1.07 MN
b) 2.14 MN
c) 4.28 MN
d) 4.35 MN

Answer: a
Clarification: tanθ=a/g
tanθ=4.5/9.8
θ=24.64⁰
h= d+(L/2)tanθ
= 2.5+3.5tan24.64
= 4.1 m

F=wAĥ
=9810*2.68*4.1
= 1.07 MN.

5. A tank containing water upto a depth of 500 mm is moving vertically upward with a constant acceleration of 2.45 m/s2. Find the force exerted by fluid of specific gravity .65 on the side of tank,width of tank is 1m.
a) 996.1 N
b) 1992.2 N
c) 498.06 N
d) 124.5 N

Answer: a
Clarification: p=ρ*g*h*(1+a/g)
=650*9.81*0.5*(1+2.45/9.81)
=3984.5 N/m2
F=wAĥ
= 650*9.81*0.5*0.5*3984.5
= 996.1N.

6. A tank containing water upto a depth of 750 mm is moving vertically downward with a constant acceleration of 3.45 m/s2. Find the force exerted by fluid of specific gravity .85 on the side of tank,width of tank is 2m
a) 2682.75 N
b) 5365.5 N
c) 1341.25 N
d) 4024.5 N

Answer: a
Clarification: p=ρ*g*h*(1-a/g)
=750*9.81*0.75*(1-3.45/9.81)
=3577 N/m2
F=wAĥ
= 0.5*0.75*3984.5*2
= 2682.75 N.

7. A tank containing water upto a depth of 650 mm is stationary. Find the force exerted by fluid of specific gravity .55 on the side of tank,width of tank is 1.5m
a) 1709.9 N
b) 3419.4N
c) 6838.8 N
d) 1367.75 N

Answer: a
Clarification: p=ρ*g*h
=550*9.81*0.65
=3507 N/m2
F=wAĥ
= 0.5*0.65*3507*1.5
= 1709.7N.

8. The pressure intensity at the bottom remains same, even if the tank moves with constant horizontal acceleration.
a) True
b) False

Answer: b
Clarification: The pressure intensity at the bottom differs due to variation in height as tank moves with constant acceleration.

9. There will be development of shear stress due to the dynamic motion of tank or container.
a) True
b) False

Answer: b
Clarification: The water in tank is at rest even if the tank is moving.

10. If the tank is moving vertically, which of its component is subjected to maximum total pressure?
a) Lower part of vertical walls
b) Higher part of vertical walls
c) Base
d) None of the mentioned

Answer: c
Clarification: Base bores the direct pressure.

250+ TOP MCQs on First Law of Thermodynamics and Answers

Fluid Mechanics Multiple Choice Questions on “First Law of Thermodynamics”.

1. First law of thermodynamics deals with _______
a) Conservation of mass
b) Conservation of momentum
c) Conservation of energy
d) Conservation of pressure

Answer: c
Clarification: First law corresponds to the law of conservation of energy. It states that energy can neither be created nor destroyed, but can be transformed from one form to the other. It follows the principle of heat transfer and energy transfer.

2. Equation of the first law of thermodynamics is ________
a) Internal Energy= Heat added into work done
b) Internal Energy= Heat rejected into work done
c) Internal Energy= Heat added divided by work done
d) Internal Energy=Heat added plus work done

Answer: d
Clarification: It is a thermodynamic expression which gives a relationship between internal energy, heat and work done. Work done on the system is positive, and work done by the system is negative. The standard unit of all these quantities is Joule.

3. During a fluid flow, the temperature is developed due to________
a) Increase in density
b) Change in pressure
c) Translational Kinetic Energy
d) Fluid level

Answer: c
Clarification: When there is a high rate of fluid flow, the molecules tend to collide with each other. At this state, the average translational kinetic energy of the particles increases. The temperature developed due to this is called as Kinetic temperature.

4. The equation for the average kinetic energy is_________
a) 0.5 KT
b) 1.5 KT
c) 2.5 KT
d) 3.5 KT

Answer: b
Clarification: The equation for kinetic energy is 0.5mv2, where m= mass and v= velocity. This equation corresponds to 1.5 KT, where K=Boltzmann’s constant and R= Gas constant.

5. An increase in enthalpy leads to an increase in __________
a) Increase in pressure
b) Increase in volume
c) Increase in internal energy
d) Increase in mass

Answer: c
Clarification: When the temperature increases, the amount of molecular interactions also increases. Using the equation from the first law of thermodynamics, internal energy also increases with the increase in temperature. Thus, increase in enthalpy leads to an increase in internal energy.

6. Entropy occurs due to _______
a) Change in macroscopic variables
b) Volumetric changes only
c) Mass changes only
d) Temperature only

Answer: a
Clarification: Entropy is related to a number of microscopic configurations. It can have some of the most specified macroscopic variables. These macroscopic variables undergo changes, which lead to a disorder or randomness.

7. What is the equation of entropy?
a) Ratio of reversible transfer of heat to absolute temperature
b) Ratio of absolute temperature to reversible heat transfer
c) Ratio of adiabatic heat to macroscopic variables
d) Ratio of macroscopic variables to adiabatic heat

Answer: a
Clarification: This equation was defined by Rudolf Clausius, who defined entropy as a ratio of reversible heat transfer to that of its absolute temperature. This definition is also called the macroscopic definition of entropy.

8. SI unit of enthalpy is_______
a) Joule/kgK
b) Joule/K
c) Joule/kg
d) K/kg

Answer: c
Clarification: Enthalpy is defined as a measurement of energy in a thermodynamic system. It is equal to the internal energy plus the product of volume and pressure. Thus, giving a unit of Joule/kg.

9. Which among this is not an exothermic reaction?
a) Combustion reaction
b) Neutralization reaction
c) Thermite reaction
d) Evaporating liquid water

Answer: d
Clarification: Exothermic reaction is a reaction that releases energy by either light or heat. It is the opposite of endothermic reactions. In this case, evaporating liquid water is an endothermic reaction. Endothermic reaction is a reaction in which the system absorbs heat from its surroundings.

10. What reaction takes place during photosynthesis?
a) Exothermic reaction
b) Endothermic reaction
c) Redox reaction
d) Combustion reaction

Answer: b
Clarification: Photosynthesis takes place by absorbing heat and energy from the surroundings. Since, endothermic reaction is a reaction in which the system absorbs heat from its surroundings, the reaction that takes place during photosynthesis is an endothermic reaction.

250+ TOP MCQs on Universal Velocity Distribution and Answers

Fluid Mechanics Multiple Choice Questions on “Universal Velocity Distribution”.

1. What is an aspect ratio in universal velocity distribution?
a) b*h
b) b/h
c) b+h
d) b-h
Answer: b
Clarification: Aspect ratio in universal velocity ratio is defined as the ratio of free surface of the fluid flow width to the depth of water. The formula is : Aspect ratio= b/h. It can also be defined as the ratio of span to the mean chord in an aero foil.

2. What is the ratio of maximum velocity to the average velocity when the fluid passes through two parallel plates?
a) 1/4
b) 1/2
c) 3/4
d) 1
Answer: c
Clarification: The maximum velocity occurs at the centre. At the centre, the radius is equal to zero. The average velocity is obtained by dividing the discharge of fluid. The discharge takes place across the cross-sectional area of the pipe.

3. The Prandtl Number approximates ___________
a) Momentum diffusivity to thermal diffusivity
b) Thermal diffusivity to momentum diffusivity
c) Shear stress to thermal diffusivity
d) Thermal diffusivity to kinematic viscosity
Answer: a
Clarification: The Prandtl number is a dimensionless number. It approximates the ratio of momentum diffusivity to thermal diffusivity. It can be expressed as Pr = v/ α(1). Where α= thermal diffusivity and v = momentum diffusivity.

4. Eddy viscosity is a turbulent transfer of_________
a) Fluid
b) Heat
c) Momentum
d) Pressure
Answer: c
Clarification: Eddy viscosity is a turbulent transfer of momentum by eddies. It gives rise to an internal fluid friction. It is in analogous to the action of molecular viscosity in a laminar fluid flow. Eddy viscosity takes place on a large scale.

5. What is the function of transilient turbulence theory?
a) Parameterizing turbulence
b) Stopping turbulence
c) Initiating turbulence
d) Detecting turbulence
Answer: a
Clarification: Transilient turbulence theory is the method used for parameterizing turbulence. Its main function is to allow all non-local vertical mixing between every pair of grid points. It happens in mainly in the vertical column.

6. What is the formula for kinematic eddy viscosity?
a) Eddy viscosity / kinematic viscosity
b) Eddy viscosity * kinematic viscosity
c) Eddy viscosity / mass density
d) Eddy viscosity / dynamic viscosity
Answer: c
Clarification: Kinematic eddy viscosity is defined as the ratio between Eddy viscosity and mass density of the fluid. It happens mainly at one hundred times the molecular kinematic viscosity. It is in the order 1m2s-1.

7. Eddy diffusion happens due to_________
a) Eddy motion
b) Fluid motion
c) Water constraint
d) Eddy constraint
Answer: a
Clarification: Eddy diffusion happens due to Eddy motion. This eddy motion is created due to fluid mixing. The fluid mixture causes the formation of eddies. Eddies can vary in size from small microscales to subtropical scales.

8. When is the fluid called laminar?
a) Reynolds number is greater than 2000
b) Reynolds number is less than 2000
c) The density of the fluid is high
d) Low viscosity
Answer: b
Clarification: Reynolds number is a dimensionless quantity. It helps to predict the flow pattern in fluid mechanics. At low Reynolds number, the flow has a very low density, due to which the value of Reynolds number is less than 2000.

9. When is a fluid called turbulent?
a) Reynolds number is greater than 2000
b) Reynolds number is less than 2000
c) The density of the fluid is low
d) High viscosity of fluid
Answer: a
Clarification: Reynolds number is a dimensionless quantity. It helps to predict the flow pattern in fluid mechanics. At high Reynolds number, the flow has a very high density, due to which the value of Reynolds number is greater than 2000.

10. Coefficient of friction of a laminar flow is_________
a) Re/16
b) Re/64
c) 16/Re
d) 64/Re
Answer: c
Clarification: Coefficient of friction is defined as the value that shows relationship between force and the normal reaction. It is mainly used to find out an object’s normal force and frictional force. Thus, it is equal to 16/Re.

250+ TOP MCQs on Model Testing of Partially Submerged Bodies and Answers

Fluid Mechanics Multiple Choice Questions on “Model Testing of Partially Submerged Bodies”.

1. What is model testing?
a) Performance testing
b) Partial testing
c) Function testing
d) Overall testing
Answer: a
Clarification: The process in fluid mechanics that is used to study the complex fluid dynamics is called as model testing. It is a performance testing. It helps to test models after a standard scaling. Models are usually smaller than the final design.

2. The performance test is completed after completion of________
a) Casing inspection
b) Regulation
c) Pump enhancement
d) Hydrostatic check
Answer: a
Clarification: The pump casting test starts with the inspection of material. It is a Non-destructive testing method. It is completed after completion of casting inspection. It depends on the pump design.

3. Which test is performed after the pump inspection?
a) Casing inspection
b) Casing hydrostatic test
c) NPSH test
d) Mechanical running test
Answer: b
Clarification: After the inspection, the pump casing hydrostatic test is performed. It takes place only after successful completion of the pump casing inspection.

4. The pump hydrostatic test is tested at __________
a) 2 times the maximum allowable work pressure
b) 3 times the maximum allowable work pressure
c) 5 times the maximum allowable work pressure
d) 1.5 times the maximum allowable work pressure
Answer: d
Clarification: The pump hydrostatic test is tested at 1.5 times the maximum allowable work pressure. It can be found out on the pump datasheet. The pump inspector does not require the calculation of pressure test.

5. What does SME stand for?
a) Subject mass export
b) Subject mass expert
c) Subject matter expert
d) Subject matter export
Answer: c
Clarification: SME stands for Subject Matter Expert. After the inspector has made an inspection on the finished material. It is further sent to the SME. The main function of the SME is to approve the finished material.

6. What does NPSH stand for?
a) Net positive suction head
b) Net positive super head
c) Net planar suction head
d) Non-planar suction head
Answer: a
Clarification: NPSH stands for Net Positive Suction Head. The main function of the NPSH test is to measure the ability of the pump. It helps to avoid cavitation at the inlet section of the pump.

7. How long is the pump mechanical run test performed?
a) 1 hour
b) 2 hours
c) 3 hours
d) 4 hours
Answer: d
Clarification: Pump Mechanical run test is performed for nearly 4 hours. Its main function is to prove that pump works under stable condition. It also helps to determine if all the variables are within the acceptance range.

8. Which among the following is not a pump operating parameter?
a) Power consumption
b) Bearing temperature
c) Density
d) Shaft speed
Answer: c
Clarification: Every parameter plays an important role in determining the pump operation. Density is not a parameter on pump mechanical run test. Each parameter operate for nearly 10 to 15 minutes.

9. A test that is performed at different flow rates is__________
a) Casing inspection
b) Casing hydrostatic test
c) NPSH test
d) Vibration test
Answer: d
Clarification: Pump vibration testing is performed during the performance test at different flow rates. It also takes place during the mechanical running test at a rated flow rate.

10. What does FFT in vibration testing stand for?
a) Fast Fourier Transformation
b) Fast Foil Temperature
c) Fast Foil Transformation
d) Feature Fourier Transformation
Answer: a
Clarification: FFT stands for Fast Fourier Transformation. Depending on the pump design, housing and vibration it is measured and plotted. FFT is a spectrum which denotes each data point from minimum to maximum.