Parallell Multigrid DNS/LES Methods for Time-Dependent Compressible Turbulent Flow Around 3-D Airfoils

摘要

Direct numerical simulation has been carried out to simulate the flow around a slender flat-plate delta wing at 12.5 deg angle of attack. Two Reynolds numbers have been selected. At a lower Reynolds number of 5 x 104, the flow is stable and dominated by a pair of leading-edge primary vortices. At a higher Reynolds number of 1.96 x 105, small-scale vortical structures are shedding from the leading-edge. It has been found that the shedding of the small-scale vortical structures originates not only from the Kelvin-Helmholtz type instability of the leading-edge shear layer, but also from the separation of the secondary vortex from the wing surface. The interaction between the secondary vortex and the Kelvin-Helmholtz type vortex is of particular interest. The periods of vortex shedding are obtained from the time series of velocity components. The distributions of the temporal-averaged velocity near the upper surface of the delta wing obtained from the computational results agree well with those from the experiment of Rieley Lowson (1998). But the steady small- scale vortical structures observed in the same experiment have not been found in the current simulation results. However, some unsteady vortical structures were also observed in the experiment, which could be related to the unsteady small vortices found in the computational results.