Stoßfront

Stoßfront, literally translated as "shock front" in German, denotes the propagating boundary across which a shock wave or a disturbance induces abrupt changes in fluid properties. It is a fundamental concept in compressible fluid dynamics and wave propagation.

In compressible flows, the Stoßfront is the surface separating the undisturbed upstream flow from the compressed, slowed, and heated downstream flow behind the shock. Across the front, pressure, density, and temperature rise, while the flow velocity decreases. The relationship between the upstream and downstream states is described by the Rankine–Hugoniot conditions; the orientation of the front distinguishes between normal and oblique shocks.

The shock front travels faster than the local speed of sound, is typically very thin compared with macroscopic flow scales, and dissipates energy as heat. In strong shocks, chemical reactions or phase changes may occur, as in detonation phenomena. Shock fronts also play a central role in various fields, including astrophysics and high-energy physics, where they describe features such as supernova–remnant expansions, stellar winds, or jet interactions.

In meteorology, the term Stoßfront is also used to denote a gust front—the leading edge of a cooler air outflow from a thunderstorm. This gust front can produce sudden wind gusts, rapid changes in humidity and temperature, and the onset of new weather hazards at the surface.