This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses 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

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Explanation: 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

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Explanation: 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

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Explanation: The Prandtl number is a dimensionless number. It approximates the ratio of momentum diffusivity to thermal diffusivity. It can be expressed as P

_{r}= 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

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Explanation: 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

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Explanation: 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

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Explanation: 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 1m

^{2}s

^{-1}.

7. Eddy diffusion happens due to_________

a) Eddy motion

b) Fluid motion

c) Water constraint

d) Eddy constraint

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Explanation: 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

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Explanation: 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

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Explanation: 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) R_{e}/16

b) R_{e}/64

c) 16/R_{e}

d) 64/R_{e}

View Answer

Explanation: 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/R

_{e}.

**Sanfoundry Global Education & Learning Series – Fluid Mechanics.**

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