A Shock-Wave/Free Turbulence Interaction

Summary

In an unsteady flow, the conditions of dynamic compatibility on both sides of a discontinuity cause the shock wave velocity to appear as an additional unknown. The shock wave turbulence can therefore be examined from two points of view: first, as a fixed discontinuity, the turbulence amplification can be summarized using a few notions of rapid distortion theory; second, the shock wave disturbances and the consequences on the apparent fluctuation level can be considered as a problem of intermittence. These two aspects are combined and interrelated, but the relative importance of intermittency effects depends mainly on the ratio c’/Δc-̄ which represents the incident turbulence level and the mean step through the shock. This study examines the experimental case of free turbulence subjected to a shock wave. The evolution of the field of turbulence is characterized on the basis of scale and level measurements, and the shock wave disturbances are described using appropriate signal processing techniques. The results are compared with those obtained in two different types of phenomenological analysis: amplification by rapid distortion and secondly an intermittence diagram associated with rippling of the shock wave.