Numerical Simulation of the Impingement of a Streamwise Vortex on a Plate

The flow field generated by the impingement of a della-wing vortex on a plate is examined computationally. The flow is simulated by solving the unsteady, three-dimensional Navier-Slokes equations on an overset grid system using a time accurate, implicit Beam and Warming algorithm. Comparison of the computed solutions for two levels of mesh resolution indicates that no additional flow features appear with grid refinement. Both the mean and unsteady flow structures are examined. Over the delta wing the (low exhibits a spiral vortex breakdown induced by the plate. Underneath the plate a highly unsteady, large-scale (owl-type) stall region is formed and results in the shedding of hairpin-like vortical structures. On the top surface of the plate a shallow separation region also exists outboard of the vortex impingement location. These separated flow features result from the spanwise variation in effective angle of attack created by the incoming vortex system. Also present over the upper surface is a mean longitudinal vonical structure arising from the passage of segments of the spiral filament. The frequency of the surface pressure fluctuations at a point on the plate leading edge that corresponds to the spiral mode of breakdown is found to be in agreement with experimental measurements. The mutual interaction between the breakdown and the stalled flow is explored. A pronounced sensitivity of breakdown location to the degree of obstruction created by the plate separation is found. This feedback effect might suggest possible flow control strategies.