The shape of a supersonic diffuser that slows down a supersonic flow to subsonic flow is
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- converging
- diverging
- diverging–converging
- converging–diverging
The Correct Option is D
Solution and Explanation
Step 1: Behavior in subsonic flow.
A subsonic diffuser uses a diverging passage to slow down the flow because pressure increases when the area increases.
Step 2: Behavior in supersonic flow.
In contrast, for supersonic speeds, the relation is reversed: a converging passage causes the flow to decelerate. So to convert supersonic flow into subsonic, the diffuser must first converge.
Step 3: Shock and further diffusion.
After the converging part slows the flow to near sonic speed, a shock or pressure rise occurs, and a diverging shape helps complete the subsonic diffusion.
Thus, a converging–diverging (C–D) diffuser is used.
Final Answer: converging–diverging
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