A Stereo PIV Investigation of a Vortex Breakdown Above a Delta Wing by Analysis of the Vorticity Field.

Abstract

The vortex breakdown above a generic delta wing was experimentally investigated in order to contribute to the better understanding of this flow phenomenon. The velocity field inside the breakdown region was measured with a three component Particle Image Velocimetry (PIV) system with a high spatial resolution and accuracy, such that the vortical structure could be analysed based on the vorticity field. One research goal was to get more information about the physical mechanism which lead to the dominant vortex breakdown phenomenon. Another important goal of the performed measurement campaign was to investigate the influence of the lower sweep angle on the flow structures. Additionally we compared our PIV and force measurement data with results of numerical simulations and the therewith identified structure of the vortex breakdown in the front part of the delta wing. We were able to confirm the occurrence of a bubble type vortex breakdown predicted by the numerical simulations.