Question

For a flow a Prandtl-Meyer expansion wave is

• A. Mach Number remains constant
• B. Entropy remains constant
• C. Density remains constant
• D. Temperature remains constant

Hint:

Remember that in any isentropic process, entropy remains unchanged, which is characteristic of idealized, reversible, adiabatic processes.

Answer 1

The Correct Option is B

Step 1: Understand the Prandtl-Meyer Expansion Wave.
Prandtl-Meyer expansion waves occur when a supersonic flow encounters a convex corner, leading to an expansion process that turns the flow away from the corner.
Step 2: Analyze the Expansion Process.
In the expansion process, the flow is isentropic (no heat transfer, no entropy change), which results in a decrease in pressure and temperature, while the Mach number increases due to the acceleration of the flow.
Step 3: Conclusion on Properties.
As the expansion is isentropic, entropy remains constant. The Mach number, density, and temperature do not remain constant as they all change due to the expansion.