Computation of shock buffet onset for a conventional and supercritical airfoil

This is a study of recent flow and turbulence models applied to the problem of shock buffet onset. The accuracy of the interactive boundary layer and the thin layer Navier-Stokes equations solved with recent upwind techniques using similar transport field equation turbulence models is assessed for standard steady test cases, including conditions having significant shock separation. The two methods are then used a study of the shock buffet onset region of a supercritical airfoil, and airfoil having strong trailing edge separation, and found to compare well. A Reynolds scaling effect in the onset of the shock buffeting of the supercritical airfoil computed with the interactive boundary layer method is found to compare well with that observed experimentally. This is used to argue that the experimental data are of conditions very near shock buffet onset. The methods are next applied to a conventional airfoil. Steady shock separated computations are shown to compare well. Computations in the shock buffeting region using the two methods, however, do not. These findings are discussed in connection with possible mechanisms important in the. onset of shock buffet.

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