Numerical investigation of shock oscillation in transonic buffeting flows

Shock wave/boundary layer interaction with separation may induce large-scale instabilities involving the whole field. This phenomenon, known as transonic buffeting, causes potentially dangerous vibrations, negative effect on flight stability and reduces the lifetime of aircraft structures. In the present work, numerical simulations have been performed to investigate the buffeting phenomenon over a supercritical OAT15A airfoil. Firstly, the reason for the occurrence of shock wave oscillation phenomena and lift coefficient fluctuations with the shock movement characteristics in a period of oscillation was explained. Secondly, multiple sets of O-type structure OAT15A airfoil grid were generated to confer the effect of first layer height on the wing surface and nodes of different density on the airfoil surface. Then different non-dimensional time steps from 0.012 to 0.11 were selected to investigate the effect of physical time step on the amplitude and frequency of the unsteady load. Finally, URANS simulations were performed to test the effect of number of pseudo time iterations and the angle of attack on the simulated buffeting characteristics. The numerical predictions showed that the oscillation shock result could be qualitatively reproduced by URANS but the accuracy on pressure fluctuation seems strongly influenced by several numerical aspects.