Condensation Shock

(or condensation shock wave), a special form of shock wave. It occurs in an accelerating supersonic gas flow as a result of the condensation of vapors contained in the gas.

A condensation shock is usually observed in a supersonic nozzle when the accelerated motion of the gas is accompanied by a monotonic decrease in the gas’s temperature and a corresponding increase in its relative humidity. In some cross sections of the nozzle the relative humidity reaches 100 percent (the saturation point), and further cooling results in condensation. The condensation of moisture in the form of a condensation shock occurs in the cross sections of the nozzle where the Mach number M = 1.2–1.4.

A condensation shock has an X-shaped form. Its reflection from the surface of the nozzle causes fluctuations in the parameters of the flowing gas—in pressure, velocity, temperature, and entropy. This poses substantial difficulties for experimental investigations. For this reason, present-day supersonic wind tunnels are equipped with special devices for air drying.