Supersonic wind tunnel

A supersonic wind tunnel has a large power demand, so most are designed for intermittent instead of continuous operation.

The first supersonic wind tunnel (with a cross section of 2 cm) was built in National Physical Laboratory in England, and started working in 1922.

The power required to run a supersonic wind tunnel is enormous, of the order of 50 MW per square meter of test section cross-sectional area.

Some large countries have built major supersonic tunnels that run continuously; one is shown in the photo.

Tunnels such as a Ludwieg tube have short test times (usually less than one second), relatively high Reynolds number, and low power requirements.

Engineers check an aircraft model before a test run in the Supersonic Wind Tunnel at Lewis Flight Propulsion Laboratory .
Schlieren photography is often used to capture images of gas flow and shock waves in supersonic wind tunnels. Here, Mach 4 flow over a pitot probe is observed by schlieren optics in the Penn State Supersonic Wind Tunnel. The flow direction is left-to-right.