Compressible Flow Fundamentals Questions and Answers

Consider the following statements about the speed of sound in a perfect gas:

1. It is proportional to the square root of the absolute temperature.

2. It is independent of the pressure at a fixed temperature.

3. It increases with altitude throughout the troposphere.

Which of the statements given above is or are correct?

Consider the following statements about a choked converging nozzle:

1. The mass flow rate is fixed by the stagnation conditions and the throat area.

2. Lowering the back pressure further does not change the mass flow.

3. Raising the stagnation pressure does not change the mass flow.

Which of the statements given above is or are correct?

Consider the following statements about the flow regimes:

1. Transonic flow contains both subsonic and supersonic regions in the same field.

2. Hypersonic flow is conventionally taken to begin above about Mach five.

3. Supersonic flow is conventionally taken to begin above about Mach 0.3.

Which of the statements given above is or are correct?

Consider the following statements about stagnation properties:

1. Stagnation temperature is conserved in any adiabatic flow without work.

2. Stagnation pressure is conserved only in isentropic flow.

3. Stagnation temperature falls across a normal shock.

Which of the statements given above is or are correct?

Consider the following statements about the Mach cone in supersonic flow:

1. Its half-angle is the inverse sine of the reciprocal of the Mach number.

2. It becomes more slender as the Mach number increases.

3. It exists in subsonic flow with a half-angle greater than 90 degrees.

Which of the statements given above is or are correct?

Consider the following statements about the Prandtl-Glauert correction:

1. It raises the predicted pressure and lift coefficients as Mach number increases.

2. It is a linearised correction valid only below the critical Mach number.

3. It applies equally well in supersonic flow.

Which of the statements given above is or are correct?

Match each Mach number range in List I with the regime it describes in List II.

List I

A. Below about 0.3

B. About 0.8 to 1.2

C. Above 1.2 but below 5

D. Above about 5

List II

1. Supersonic

2. Effectively incompressible

3. Hypersonic

4. Transonic

Select the correct match.

Match each quantity in List I with its behaviour across a normal shock in List II.

List I

A. Stagnation temperature

B. Stagnation pressure

C. Entropy

D. Static pressure

List II

1. Falls

2. Unchanged

3. Rises

4. Rises sharply

Select the correct match.

Match each duct condition in List I with its effect on the flow in List II.

List I

A. Converging duct, subsonic flow

B. Diverging duct, subsonic flow

C. Converging duct, supersonic flow

D. Diverging duct, supersonic flow

List II

1. Flow decelerates

2. Flow accelerates

3. Flow accelerates and pressure falls

4. Flow decelerates and pressure rises

Select the correct match.

Match each term in List I with its definition in List II.

List I

A. Critical Mach number

B. Drag-divergence Mach number

C. Mach angle

D. Stagnation temperature

List II

1. Where drag begins to rise sharply in transonic flow

2. Where sonic flow first appears on the surface

3. The temperature after an adiabatic deceleration to rest

4. The half-angle of the cone bounding weak disturbances

Select the correct match.