The Study Of Receptivity Of Supersonic Boundary-layer To Local Periodic Disturbance In Free-stream

The study for the stability of boundary-layer is of significant importance for both theoretical research and engineering applications,while the receptivity is one of the important parts of boundary-layer stability.The supersonic boundary-layer receptivity to local disturbance in freestream is studied by DNS.The mode of the instabile wave which is excited in boundary is studied in this paper,the affections to instabilities by the frequency and range of local desturbance is discussed,the excition mechanism is also studied.The main conclutions are listed below :1. When introduces a periodic local force to the free-stream, the disturb velocity divergence changes periodicly near the force.This is equal to add sources in the flow. The sources interacte with the boundary and produce local disturbance in the boundary.2. The local disturbance can induce wave that propagates downstream, when the frequency of the force is equal to the frequency of the instable wave, the instable wave can be induced. If the amplitude of the force is small, the propagatation of the instable wave accord with the linear stability theory.3. Under a fixed frequency, the engery of the instable wave relates to the size of the force, there is a optimal size that can induce strongest instable wave.