Shock tube

A shock tube is a wind tunnel, with which for very short times (0.24 s ) in a small test section ( 0.8 m long and 1.2 m cross-section ) can generate very high flow rates. Measuring the duration depends on the length of the two pipes. The test is terminated when the light reflected at the front wall shock wave reaches the measuring section.

The shock tube is a closed system of two tubes that are initially separated by a membrane. One of the two tubes, the compression tube is inflated to a high pressure. The other tube shock tube is filled with a significantly lower pressure in the millibar range with the test gas to be examined. In the two tube halves, different gases may be present. With air can reach a maximum of Mach 6. With other gases (argon, helium, nitrogen, hydrogen) can theoretically be achieved up to Mach 26.

By mechanical action or reaching the breaking point when inflating the membrane is burst and caused the collision. Here below a rarefaction wave in the compression tube and a shock wave continuing in the shock tube. Due to the shock wave, the gas in the shock tube is strongly compressed and heated.

In the High Enthalpy Shock Tunnel, a large experimental facility at the German Centre for Aerospace, a shock tube is used by 60 meters in length to simulate the physical conditions during re-entry of landing capsules of spacecraft into Earth's atmosphere. Temperatures of up to 10,000 Kelvin and flow rates of up to 6,000 m / s can be achieved.