Source-pulsation vortex simulation of turbulentseparation bubbles with sinusoidal perturbations

Abstract

Numerical studies are made of the active control of turbulent leadingedge separation bubbles. A time-dependent sinusoidal source pulsation is generated at the separation point. In order to make a numerial simulation, a source-pulsation vortex method (SPVM) is proposed. For purposes of comparison and verification a free-stream pulsation vortex method is also introduced. While the free-stream pulsation affects whole flow structures by capturing large-scale vortices at particular positions, the effect of source polsation is restricted to separation point. Although the effect of perturbation due to pulsation near separation point is similar in both cases, the time evolution of flow patterns is quite different. It correlates reasonably with relevant experiments in which perturbation is produced with an oscillating jet at the separation edge. In both cases, reduction of reattachment length is observed. The effects of pulsating frequency and strength on the separation bubble are also scrutinized. In order to investigate the reduction mechanism of reattachment length in SPVM, various cross-correlations and convection velocities are evaluated. It is found that in source pulsation convection velocity is closely associated with corresponding pulsating frequency.