116
5 Supersonic Wind Tunnels
Fig. 5.1 Evolution of the Mach number according to the cross-section area ratio
Pressure evolution
Temperature evolution
(a)
(b)
Fig. 5.2 Isentropic expansion in a nozzle
in a tank. The pressure ratio between upstream and downstream can be increased
by connecting the wind tunnel diffuser to a large volume tank where a very low
pressure is established before testing. Such an installation is called an intermittent
wind tunnel, the time during which the supersonic flow is established being limited
by the capacity of the compressed air storage or by the volume of the vacuum tank
and also by the quality of the diffuser. Indeed, a good diffuser can recover a higher
pressure after the minimum reached in the test chamber, hence the ability to maintain
the flow with a higher pressure in the vacuum tank.
5 Supersonic Wind Tunnels
Fig. 5.1 Evolution of the Mach number according to the cross-section area ratio
Pressure evolution
Temperature evolution
(a)
(b)
Fig. 5.2 Isentropic expansion in a nozzle
in a tank. The pressure ratio between upstream and downstream can be increased
by connecting the wind tunnel diffuser to a large volume tank where a very low
pressure is established before testing. Such an installation is called an intermittent
wind tunnel, the time during which the supersonic flow is established being limited
by the capacity of the compressed air storage or by the volume of the vacuum tank
and also by the quality of the diffuser. Indeed, a good diffuser can recover a higher
pressure after the minimum reached in the test chamber, hence the ability to maintain
the flow with a higher pressure in the vacuum tank.