Computation Of A Kelvin Helmholtz Instability For Delta Wing Vortex Flows PDF Download

The three-dimensional separated flow around a slender flat-plate delta wing with sharp leading-edge at a 12.5 deg angle of attack has been studied by solving the full compressible Navier-Stokes equations in the generalized curvilinear coordinates. The time integration is carried out by using the second-order LU-SGS implicit scheme. A fourth-order centered compact difference scheme is used for spatial derivatives. A sixth-order implicit filter is employed to reduce numerical oscillation. Non-reflecting boundary conditions are imposed at the far-field and outlet boundaries to avoid possible non-physical wave reflection. Parallel computing based on Message Passing Interface (MPI) has been utilized to improve the performance of the code. Two Reynolds numbers have been selected. At a lower Reynolds number of 50000 based on the chord length and the freestream velocity, the flow is stable and dominated by a pair of leading edge primary vortices. At a higher Reynolds number of 196000, the small-scale vortex shedding is observed near the leading-edge of the delta wing. The computational results are compared with the experimental work of Riley & Lowson (1998). The periodic shedding of small-scale vortical structures near the leading-edge has been studied in detail, and the vortex shedding is found to be associated with the Kelvin-Helmholtz-type instability and the secondary vortex. The period of vortex shedding is obtained from the time series of the three velocity components recorded near the leading-edge. The time-averaged features of the vortical structures are also discussed.