When is flow considered to be compressible?

If the flow Mach number is greater than one

If the percentage change in the density of the flow is more than 15%

If the flow is more than Mach number 0.3 or the percentage change in density is more than 5%

If the flow is less than Mach number 0.5 or the percentage change in density is more than 10%

Correct Answer : If the flow is more than Mach number 0.3 or the percentage change in density is more than 5%

Explanation : Compressible effects are observed in all flow regimes but its effects are only significant from Mach number 0.3 or if the percentage change in density of the flow is more than 5%.

Recently Updated in Aerodynamics Questions

What will happen when the wedge angle is finite?

Streamlines over the wedge are parallel to the flow ahead of the wedge

Finite disturbances will be introduced and the wave will be called a shock wave

The deviation of streamlines will be finite and pressure will decrease across the shock wave

Small disturbances will be introduced and we can consider these to be identical to sound pulses

Correct Answer : Option (B) : Finite disturbances will be introduced and the wave will be called a shock wave

Explanation : When the wedge angle is finite, direction of flow changes rapidly and this deviation causes shock wave. There is pressure increase across the shock wave but total pressure reduces since velocity reduces.

What is true about a supersonic flow around a wedge?

The flow changes its direction abruptly and pressure decreases with acceleration

There is a sudden change in flow direction at the body and pressure increases downstream of the shock

The flow changes its direction smoothly and pressure decreases with acceleration

The flow changes its direction smoothly and pressure increases downstream with acceleration

Correct Answer : Option (B) : There is a sudden change in flow direction at the body and pressure increases downstream of the shock

Explanation : When the flow is supersonic around a wedge, it is observed that there is a sudden change in flow direction at the body and pressure increases downstream of the shock.

Which is not a property of Mach Wave?

Adiabatic

Reversible

Isentropic

Non-isentropic

Correct Answer : Option (D) : Non-isentropic

Explanation : Flow across a Mach wave follows an isentropic process. Isentropic process is characterized by its adiabatic and reversible process. Stagnation properties remains constant across the wave.