Shock Waves

Compressible flow is the area of fluid mechanics that deals with fluids in which the fluid density varies significantly in response to a change in pressure. Compressibility effects are typically considered significant if the Mach number (the ratio of the flow velocity to the local speed of sound) of the flow exceeds 0.3. Applications for compressible flow include the aerodynamics of high speed aircrafts, the flow through the turbo compressor, turbine and nozzle of a jet engine, the deployment of airbags etc..

The most distinct differences between the compressible and incompressible flow models are that the compressible flow model allows for the existence of shock waves and choked flow. Shock waves are an important aspect of compressible flow and occur in most practical situations where supersonic flow exists. Shock waves form when the speed of a gas changes by more than the speed of sound.At the region where this occurs sound waves traveling against the flow reach a point where they cannot travel any further upstream and the pressure progressively builds in that region, and a high pressure shock wave rapidly forms.

This verification test case first introduced by G.A. Sod consists of a tube closed at both ends, with a diaphragm separating a region of high-pressure gas on the left from a region of low pressure gas on the right. When the diaphragm is removed, an expansion wave travels to the left and a shock wave to the right (Read more).
This verification test case shows the impact of an incoming oblique shock wave on a solid wall. The reflection of a shock wave is also a shock wave thus dividing the fluid domain in three zones with three distinct fluid velocities, pressure, density and temperature that can be solved analytically (Read more).
This validation test case shows how the solver handles the complex interactions that occur when an oblique shock wave impacts a solid wall's boundary layer (Boundary layer separation, first reflected shock wave upstream of the incident shock wave impact, existence of a second reflected shock wave, etc..) (Read more).
A special poster session was run during the 18th International Symposium on Shock Waves, held on July 21 - 26, 1991, in Sendai, Japan where the 2-D planar shock wave diffraction over a 90 degree sharp corner was selected as a benchmark problem for compressible CFD codes (Read more).
This benchmarking test case features an incoming supersonic flow in a wind tunnel meeting a step. Once the flow reaches the step, shock waves appear and are reflected on the different wind tunnel boundaries. The objective of this test case is to study the development of the flow through time and specifically the varying impact locations of the shock waves (Read more).
Modern high speed aircrafts usually fly in transonic flows where there is mixed sub- and supersonic local flow in the same flowfield (typically with freestream Mach numbers from M = 0.7 or 0.8 to 1.3). Usually the supersonic region of the flow is terminated by a shock wave, allowing the flow to slow down to subsonic speeds. This benchmarking test case studies the inviscid flow over a classic NACA airfoil at transonic speed (Read more).