The speed at which just a portion of the air flowing over a wing goes supersonic is known as...

The speed at which just a portion of the air flowing over a wing goes supersonic is known as...

• A. Mach Number
• B. Critical Mach Number
• C. Free Stream Velocity
• D. Dynamic Pressure

Answer: (B)

When air speeds up over a wing, local streams can reach the speed of sound even if the overall inflow is subsonic. The quantity that marks the exact point where sonic flow first appears on the wing is the critical Mach number. It’s defined as the free-stream Mach number at which the flow first becomes sonic at some location on the surface. This threshold signals the onset of strong compressibility effects and shock formation, which change lift and drag behavior. So the speed at which just a portion of the air over the wing goes supersonic is the critical Mach number. The other terms describe different ideas: Mach number is the ratio of local speed to sound, free stream velocity is the undisturbed inflow speed, and dynamic pressure is related to velocity and density but does not specify when sonic flow begins.

When air speeds up over a wing, local streams can reach the speed of sound even if the overall inflow is subsonic. The quantity that marks the exact point where sonic flow first appears on the wing is the critical Mach number. It’s defined as the free-stream Mach number at which the flow first becomes sonic at some location on the surface. This threshold signals the onset of strong compressibility effects and shock formation, which change lift and drag behavior. So the speed at which just a portion of the air over the wing goes supersonic is the critical Mach number. The other terms describe different ideas: Mach number is the ratio of local speed to sound, free stream velocity is the undisturbed inflow speed, and dynamic pressure is related to velocity and density but does not specify when sonic flow begins.