Total pressure loss in a normal shock diffuser is less than the oblique shock diffuser.

True

False

Can Not Say

None of the above

Correct Answer : False

Explanation : In case of an oblique shock diffuser, the total pressure drop across multiple oblique hocks followed by a weak normal shock is less than a strong normal shock in case of normal shock diffuser. This is why it is preferred to opt for an oblique shock diffuser that manages to slow down the accelerated flow with lesser pressure loss.

Recently Updated in Aerodynamics Questions

What is the entropy relation between the entry and exit of an actual diffuser?

s₁ = s₂

s₁ > s₂

s₁ < s₂

s₁ s₂ = 1

Correct Answer : Option (C) : s₁ < s₂

Explaination : The flow diffuses to a slower velocity when the flow interacts with the oblique shock waves inside the diffuser. This causes the diffuser to have a normal shock wave at the end. The entropy of the exit is therefore higher than the entropy of the inlet segment.

What is the diffuser efficiency for supersonic flow?

η_D > 1

η_D = 1

η_D = 1/2

η_D < 1

Correct Answer : Option (A) : η_D > 1

Explaination : The diffuser efficiency is given by the ratio of actual total pressure ratio across the diffuser to the total pressure ratio of a hypothetical normal shock wave at test section Mach number. For a supersonic test section Mach number, the diffusers perform better than the normal shock, thus the numerator of the ratio is greater than the denominator, hence η_D > 1.

Why is the diffuser throat area greater than the nozzle throat area?

To reduce speed

Rise in entropy within diffuser

Rise in entropy within nozzle

To maintain constant mass flow rate

Correct Answer : Option (B) : Rise in entropy within diffuser

Explanation : In a supersonic wind tunnel, there are two throats present. One is that of the nozzle which is known as the first throat which has sonic speed with corresponding area as A*. The second throat is that of the diffuser which is always greater than the first throat because there’s an increase in entropy due to the presence of shock waves.