Introduction to Compressible Flows: Master Fluid Mechanics with Confidence

Question 1

The Mach number, which characterizes the compressibility of a flow, is defined as the ratio of:

Accepted Answer

Flow velocity to the local speed of sound

Answer

Local speed of sound to flow velocity

Answer

Stagnation temperature to static temperature

Answer

Stagnation pressure to static pressure

Question 2

Which of the following is a distinctive property of a shock wave in compressible flow?

Accepted Answer

Irreversible increase in entropy across the wave

Answer

Continuous pressure gradient across the wave

Answer

Adiabatic process across the wave

Answer

Constant velocity across the wave

Question 3

The Prandtl-Meyer expansion fan in compressible flow is characterized by:

Accepted Answer

Supersonic flow with increasing velocity

Answer

Subsonic flow with decreasing velocity

Answer

Isentropic flow with constant velocity

Answer

Non-isentropic flow with increasing pressure

Question 4

For air at standard atmospheric conditions, the isentropic exponent (specific heat ratio) is approximately:

Accepted Answer

1.4

Answer

1.2

Answer

1.3

Answer

1.5

Question 5

The primary distinction between the governing equations for compressible and incompressible flows is:

Accepted Answer

Inclusion of density variations in compressible flows

Answer

Neglect of viscous forces in both cases

Answer

Consideration of heat transfer only in compressible flows

Answer

Linearization of the momentum equation for incompressible flows

Question 6

Define the Mach number and its significance.

Accepted Answer

The ratio of flow velocity to the speed of sound.

Answer

The ratio of flow density to the inlet density.

Answer

The pressure gradient along the flow path.

Answer

The friction factor for the flow.

Question 7

Identify the limitation of the isentropic flow assumption.

Accepted Answer

Neglects heat transfer and friction.

Answer

Applicable only to steady flows.

Answer

Cannot be used for diffuser flow calculations.

Answer

Limited to perfect gases.

Question 8

What does the Prandtl-Meyer expansion calculate?

Accepted Answer

Flow properties downstream of an expansion fan.

Answer

Flow properties downstream of a shock wave.

Answer

Flow properties upstream of a throat.

Answer

Flow properties at the stagnation point.

Question 9

Define the critical Mach number for a Laval nozzle.

Accepted Answer

The Mach number at which the flow becomes choked.

Answer

The Mach number at which the flow becomes supersonic.

Answer

The Mach number at which the flow becomes subsonic.

Answer

The Mach number at which the flow becomes laminar.

Question 10

What fundamental principle governs the conservation of mass in compressible flows?

Accepted Answer

The continuity equation

Answer

The Navier-Stokes equations

Answer

The Euler equations

Answer

The Bernoulli equation

Question 11

Which dimensionless parameter quantifies the compressibility of a fluid?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Prandtl number

Answer

Nusselt number

Question 12

In a normal shock wave, the:

Accepted Answer

Flow velocity decreases while pressure increases

Answer

Flow velocity increases while pressure decreases

Answer

Flow velocity and pressure remain constant

Answer

Flow velocity and temperature remain constant

Question 13

How does modifying the shape of a nozzle affect the pressure, velocity, and temperature distributions in compressible nozzle flow?

Accepted Answer

Impacts all three distributions: pressure, velocity, and temperature

Answer

Changes only the pressure and velocity distributions

Answer

Has no effect on the flow distributions

Question 14

Which of the following statements is NOT a characteristic of compressible flows?

Accepted Answer

Incompressibility

Answer

Significant density changes

Answer

Subsonic and supersonic regions

Answer

Existence of shock waves

Question 15

Which governing equation describes the conservation of mass for compressible flows?

Accepted Answer

Continuity Equation

Answer

Energy Equation

Answer

Navier-Stokes Equation

Answer

Momentum Equation

Question 16

Identify the consequence of the high compressibility of hypersonic flows:

Accepted Answer

Shock wave formation

Answer

Laminar boundary layer

Answer

Low drag coefficients

Answer

Incompressible flow behavior

Question 17

Which flow regime exhibits low Mach numbers and negligible compressibility effects?

Accepted Answer

Incompressible flow

Answer

Transonic flow

Answer

Hypersonic flow

Answer

Supersonic flow

Question 18

Which assumption underpins the concept of an isentropic flow?

Accepted Answer

No entropy generation

Answer

Adiabatic flow

Answer

Reversible flow

Answer

Constant temperature

Question 19

What physical phenomenon does the Prandtl-Meyer expansion fan describe?

Accepted Answer

Expansion of supersonic flow around a convex corner

Answer

Compression of supersonic flow around a concave corner

Answer

Shock wave formation in transonic flows

Question 20

Which method is commonly used for the numerical solution of compressible flow problems?

Accepted Answer

CFD (Computational Fluid Dynamics)

Answer

Experimental measurements

Answer

Method of characteristics

Answer

Analytic methods

Question 21

What is the primary purpose of using a nozzle in a compressible flow application?

Accepted Answer

To accelerate the flow and increase the Mach number

Answer

To decelerate the flow and decrease the Mach number

Answer

To maintain constant velocity and Mach number