In a divergent nozzle, supersonic flow, which statement is true?

In a divergent nozzle, supersonic flow, which statement is true?

• A. Subsonic flow accelerates to sonic speed
• B. Subsonic flow accelerates
• C. Supersonic flow continues to accelerate
• D. Supersonic flow decelerates

Answer: (C)

The key idea is how speed changes with area in compressible flow depending on the Mach number. For flows that are already supersonic (Mach > 1), increasing the cross-sectional area causes the velocity to rise and the Mach number to increase even more. So in a divergent nozzle, where the area is expanding, a supersonic flow will continue to accelerate. That makes the statement about supersonic flow continuing to accelerate the correct one. The other options don’t fit this scenario: subsonic flow behaves differently in a divergent section and would tend to decelerate as area grows, while a supersonic flow in a divergent nozzle does not decelerate under these usual conditions.

The key idea is how speed changes with area in compressible flow depending on the Mach number. For flows that are already supersonic (Mach > 1), increasing the cross-sectional area causes the velocity to rise and the Mach number to increase even more. So in a divergent nozzle, where the area is expanding, a supersonic flow will continue to accelerate.

That makes the statement about supersonic flow continuing to accelerate the correct one. The other options don’t fit this scenario: subsonic flow behaves differently in a divergent section and would tend to decelerate as area grows, while a supersonic flow in a divergent nozzle does not decelerate under these usual conditions.