In subsonic flight, what is the effect of a divergent-shaped jet engine inlet on the incoming air?

In subsonic flight, what is the effect of a divergent-shaped jet engine inlet on the incoming air?

• A. It increases air velocity and decreases air pressure.
• B. It decreases air velocity and increases air pressure.
• C. It has no effect on air velocity or pressure.
• D. It reverses the direction of airflow.

Answer: (B)

In subsonic flight, a divergent-shaped jet engine inlet acts as a diffuser. As air flows into and through the inlet, the cross-sectional area increases, so the flow must slow down to satisfy continuity. Because slower flow in a diffuser corresponds to higher static pressure (per Bernoulli-like reasoning for subsonic speeds), the incoming air ends up with reduced velocity and increased static pressure when it reaches the compressor face. This helps deliver a steadier, higher-pressure air supply to the engine. So the effect is that the air velocity decreases and the air pressure increases. It won’t reverse flow and it isn’t left unchanged.

In subsonic flight, a divergent-shaped jet engine inlet acts as a diffuser. As air flows into and through the inlet, the cross-sectional area increases, so the flow must slow down to satisfy continuity. Because slower flow in a diffuser corresponds to higher static pressure (per Bernoulli-like reasoning for subsonic speeds), the incoming air ends up with reduced velocity and increased static pressure when it reaches the compressor face. This helps deliver a steadier, higher-pressure air supply to the engine.

So the effect is that the air velocity decreases and the air pressure increases. It won’t reverse flow and it isn’t left unchanged.