Flow Resistance

Description: This quiz aims to assess your understanding of the concept of flow resistance, which is a fundamental aspect of fluid mechanics. The questions cover various aspects of flow resistance, including its types, factors affecting it, and its implications in fluid flow systems.
Number of Questions: 15
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Tags: fluid mechanics flow resistance darcy-weisbach equation laminar and turbulent flow friction factor
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Which of the following is NOT a type of flow resistance?

  1. Skin friction

  2. Form drag

  3. Wave drag

  4. Induced drag


Correct Option: D
Explanation:

Induced drag is a type of aerodynamic drag that is generated by the lift produced by an airfoil. It is not a type of flow resistance in the context of fluid mechanics.

The Darcy-Weisbach equation is used to calculate the:

  1. Pressure drop in a pipe

  2. Velocity of a fluid in a pipe

  3. Reynolds number of a fluid

  4. Friction factor of a pipe


Correct Option: A
Explanation:

The Darcy-Weisbach equation is a fundamental equation in fluid mechanics used to calculate the pressure drop in a pipe due to frictional losses.

In laminar flow, the friction factor:

  1. Is constant

  2. Increases with Reynolds number

  3. Decreases with Reynolds number

  4. Depends on the pipe roughness


Correct Option: A
Explanation:

In laminar flow, the friction factor is constant and independent of the Reynolds number. This is because the flow is characterized by smooth, parallel layers of fluid.

Which of the following factors does NOT affect the friction factor in turbulent flow?

  1. Reynolds number

  2. Pipe roughness

  3. Fluid viscosity

  4. Pipe diameter


Correct Option: D
Explanation:

The friction factor in turbulent flow is primarily affected by the Reynolds number, pipe roughness, and fluid viscosity. Pipe diameter does not directly influence the friction factor.

The Moody diagram is used to determine the:

  1. Friction factor for a given Reynolds number and relative roughness

  2. Pressure drop in a pipe

  3. Velocity of a fluid in a pipe

  4. Reynolds number of a fluid


Correct Option: A
Explanation:

The Moody diagram is a graphical representation that provides the friction factor for a given Reynolds number and relative roughness of a pipe.

Which of the following is NOT a consequence of high flow resistance?

  1. Increased pressure drop

  2. Reduced flow rate

  3. Increased energy consumption

  4. Improved flow efficiency


Correct Option: D
Explanation:

High flow resistance leads to increased pressure drop, reduced flow rate, and increased energy consumption. It does not improve flow efficiency.

In a pipe flow, the pressure drop due to flow resistance is:

  1. Proportional to the square of the flow velocity

  2. Proportional to the flow velocity

  3. Proportional to the square root of the flow velocity

  4. Independent of the flow velocity


Correct Option: A
Explanation:

The pressure drop due to flow resistance in a pipe is proportional to the square of the flow velocity, as expressed by the Darcy-Weisbach equation.

Which of the following is NOT a method to reduce flow resistance in a pipe?

  1. Using a larger pipe diameter

  2. Using a smoother pipe surface

  3. Increasing the fluid viscosity

  4. Using a shorter pipe length


Correct Option: C
Explanation:

Increasing the fluid viscosity increases flow resistance. Using a larger pipe diameter, using a smoother pipe surface, and using a shorter pipe length are all methods to reduce flow resistance.

The phenomenon of sudden pressure drop and flow separation due to high flow resistance is known as:

  1. Cavitation

  2. Turbulence

  3. Laminar flow

  4. Stagnation point


Correct Option: A
Explanation:

Cavitation is the phenomenon of sudden pressure drop and flow separation due to high flow resistance, often leading to the formation of vapor bubbles in a liquid.

Which of the following is NOT a type of flow resistance encountered in external flows?

  1. Skin friction

  2. Form drag

  3. Wave drag

  4. Induced drag


Correct Option: D
Explanation:

Induced drag is a type of aerodynamic drag generated by the lift produced by an airfoil. It is not encountered in external flows in the context of fluid mechanics.

The friction factor in turbulent flow is primarily affected by:

  1. Reynolds number

  2. Pipe roughness

  3. Fluid viscosity

  4. All of the above


Correct Option: D
Explanation:

The friction factor in turbulent flow is primarily affected by the Reynolds number, pipe roughness, and fluid viscosity.

Which of the following is NOT a dimensionless number used to characterize flow resistance?

  1. Reynolds number

  2. Friction factor

  3. Nusselt number

  4. Prandtl number


Correct Option: C
Explanation:

The Nusselt number is a dimensionless number used to characterize heat transfer, not flow resistance. The Reynolds number and friction factor are dimensionless numbers used to characterize flow resistance.

The pressure drop due to flow resistance in a pipe is:

  1. Independent of the pipe length

  2. Proportional to the pipe length

  3. Proportional to the square of the pipe length

  4. Proportional to the cube of the pipe length


Correct Option: B
Explanation:

The pressure drop due to flow resistance in a pipe is proportional to the pipe length, as expressed by the Darcy-Weisbach equation.

Which of the following is NOT a method to reduce flow resistance in an external flow?

  1. Streamlining the object's shape

  2. Reducing the object's surface roughness

  3. Increasing the object's velocity

  4. Using a larger object


Correct Option: C
Explanation:

Increasing the object's velocity increases flow resistance. Streamlining the object's shape, reducing the object's surface roughness, and using a larger object are all methods to reduce flow resistance in an external flow.

The phenomenon of sudden pressure drop and flow separation due to high flow resistance in an external flow is known as:

  1. Cavitation

  2. Turbulence

  3. Laminar flow

  4. Flow separation


Correct Option: D
Explanation:

Flow separation is the phenomenon of sudden pressure drop and flow separation due to high flow resistance in an external flow, often leading to the formation of a wake region.

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