Consider a supersonic windtunnel. What happens downstream of the throat?

Question

A) The density decreases while the pressure increases
B) The density increases while the pressure decreases
C) The temperature increases while the pressure decreases
D) The pressure decreases and the temperature decreases

Answer 1

In a supersonic wind tunnel, after the throat (where the flow reaches the speed of sound, or Mach 1), the flow transitions to supersonic conditions.

Downstream of the throat, the following occurs:

• The flow becomes supersonic, which means that the velocity of the air continues to increase.
• As the flow accelerates, the pressure decreases and the density decreases.

This means that the correct answer among the options provided is:

D) The pressure decreases and the temperature decreases.

In summary, downstream of the throat in a supersonic wind tunnel, both pressure and temperature decrease as the flow accelerates.