The Mach 3.5 blow-down wind tunnel S-4 has an 8 cm x 10 cm test section. Air is supplied at stagnation pressures from 3 to 18 bar and a supersonic ejector can be used to decrease the exhaust pressure downstream of a variable geometry diffuser. A typical unit Reynolds number for the S-4 is 5 x 107/m.
Depending on the stagnation pressure, the facility can achieve test times from 8 to 25 minutes. Model incidence can be adjusted in the range -10° to +10°, and models can be injected
rapidly into the air-stream when required.
The tunnel is equipped with shadow and schlieren systems. Instrumentation includes scani-valves for pressure measurements and three-component strain gauge balances.