Compressible Flow MCQs - Fluid Mechanics

Compressible Flow MCQs - Fluid Mechanics: This section contains the multiple-choice questions and answers on the fluid mechanics chapter Compressible Flow. practice these MCQs to learn and enhance the knowledge of Compressible Flow.

List of Fluid Mechanics - Compressible Flow MCQs

1. The ideal gas law, PV = nRT, is an example of which thermodynamic relation?

  1. Joule-Thomson Relation
  2. Maxwell's Relations
  3. Clausius-Clapeyron Equation
  4. Equation of State

Answer: D) Equation of State


The ideal gas law is a fundamental equation of state that relates pressure (P), volume (V), temperature (T), and the number of moles (n) of an ideal gas.

2. During an isothermal expansion of an ideal gas, what happens to its pressure and volume?

  1. Pressure increases, volume increases
  2. Pressure decreases, volume increases
  3. Pressure increases, volume decreases
  4. Pressure decreases, volume decreases

Answer: B) Pressure decreases, volume increases


In an isothermal expansion, the pressure decreases while the volume increases to maintain a constant temperature.

3. What is the mathematical representation of an isothermal process on a P-V diagram?

  1. A horizontal line
  2. A curved line
  3. A diagonal line
  4. A vertical line

Answer: A) A horizontal line


On a P-V diagram, an isothermal process is represented as a horizontal line because the temperature remains constant.

4. Which thermodynamic process has the highest work output for an ideal gas?

  1. Isothermal expansion
  2. Adiabatic expansion
  3. Isobaric expansion
  4. Isochoric expansion

Answer: A) Isothermal expansion


Isothermal expansion results in the highest work output for an ideal gas because the temperature remains constant, allowing for maximum utilization of energy

5. In an adiabatic expansion of an ideal gas, what happens to its temperature?

  1. Depends on the initial conditions
  2. Decreases
  3. Remains constant
  4. Increases

Answer: B) Decreases


During an adiabatic expansion, the temperature of an ideal gas decreases because the internal energy decreases.

6. What does the term ∇ · (AV) represent in the continuity equation for compressible flow?

  1. Rate of change of density
  2. Rate of change of velocity
  3. Mass flow rate
  4. Rate of change of pressure

Answer: C) Mass flow rate


∇ · (AV) represents the mass flow rate through a differential control volume.

7. The momentum equation relates changes in ____ to forces acting on a fluid.

  1. Pressure
  2. Velocity
  3. Density
  4. Temperature

Answer: B) Velocity


The momentum equation relates changes in velocity to the forces acting on a fluid, expressing the conservation of linear momentum.

8. What is the relationship between the bulk modulus (K) and the velocity of sound (v) for a fluid?

  1. v = √(K/ρ)
  2. v = √(ρ/K)
  3. v = ρ/K
  4. v = Kρ

Answer: A) v = √(K/ρ)


The correct relationship between the velocity of sound (v), bulk modulus (K), and density (ρ) for a fluid is v = √(K/ρ).

9. Which parameter does the bulk modulus (K) represent in a fluid?

  1. Elasticity
  2. Pressure
  3. Temperature
  4. Viscosity

Answer: A) Elasticity


The bulk modulus (K) measures the elasticity or compressibility of a fluid. It quantifies how a fluid responds to changes in pressure.

10. What does a Mach number of 1.0 signify in a compressible flow?

  1. Choked flow
  2. Supersonic flow
  3. Subsonic flow
  4. Sonic flow

Answer: D) Sonic flow


A Mach number of 1.0 signifies sonic flow, where the flow velocity is exactly equal to the speed of sound in the fluid.

11. How does an increase in Mach number affect the Mach angle in a compressible flow?

  1. The Mach angle decreases
  2. The Mach angle remains constant
  3. It depends on other flow properties
  4. The Mach angle increases

Answer: A) The Mach angle decreases.


As the Mach number increases, the Mach angle decreases, indicating a transition from subsonic to supersonic flow.

12. How does the Mach number change as the fluid passes through the "Zone of Action"?

  1. It increases
  2. It decreases
  3. It remains constant
  4. It varies randomly

Answer: A) It increases


In the "Zone of Action", the Mach number typically increases as the flow accelerates, causing a decrease in pressure and an increase in velocity.

13. What is the purpose of the Pitot tube in a Pitot-static system?

  1. To measure atmospheric pressure
  2. To measure total pressure
  3. To measure velocity pressure
  4. To measure static pressure

Answer: B) To measure total pressure


The Pitot tube of a Pitot-static system is designed to measure the total pressure of the fluid

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