12/2/2023 0 Comments Subsonic speed gif![]() Shock waves are formed when a pressure front moves at supersonic speeds and pushes on the surrounding air. ![]() In reference to the continuum, this implies the shock wave can be treated as either a line or a plane if the flow field is two-dimensional or three-dimensional, respectively. Measurements of the thickness of shock waves in air have resulted in values around 200 nm (about 10 −5 in), which is on the same order of magnitude as the mean free path of gas molecules. In a shock wave the properties of the fluid ( density, pressure, temperature, flow velocity, Mach number) change almost instantaneously. When an object (or disturbance) moves faster than the information can propagate into the surrounding fluid, then the fluid near the disturbance cannot react or "get out of the way" before the disturbance arrives. The abruptness of change in the features of the medium, that characterize shock waves, can be viewed as a phase transition: the pressure-time diagram of a supersonic object propagating shows how the transition induced by a shock wave is analogous to a dynamic phase transition. Conical shockwave with its hyperbola-shaped ground contact zone in yellow The leading edge of the object causes a shock (left, in red) and the trailing edge of the object causes an expansion (right, in blue). In supersonic flows Pressure-time diagram at an external observation point for the case of a supersonic object propagating past the observer. The contact front trails the shock front.
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