NUMERICAL-SIMULATION OF SEPARATED BOUNDARY-LAYER FLOW

The numerical simulation of time-dependent, 2-D compressible boundary- layer flow containing a region of separation is studied. The separatio n is generated by the introduction of an adverse pressure gradient alo ng the freestream boundary. In order to validate the numerical method, a low Mach-number laminar separation bubble flow is considered, which enables an extensive comparison with incompressible results. The gene ration of an adverse pressure gradient along the freestream boundary c an be realized in various ways. An imposed decelerating flow boundary is compared with a suction technique. The effects of the strength of t he pressure gradient and the presence of small upstream perturbations on the separation bubble are also investigated. The time-averaged char acteristics of the flow are in good quantitative agreement with incomp ressible approximate theories predicting the condition for separation. The appearance of self-excited vortex shedding in unperturbed flows u nder a sufficiently strong adverse pressure gradient is consistent wit h incompressible flow simulations reported in the literature. The sati sfactory result achieved in the calculation of the low Mach-number flo w encourages the application of the numerical method to flows with str ong compressibility effects.