A New Criterion to Determine the Position of Vortex Breakdown Point

摘要

A criterion based on the vorticity magnitude of the vortex core by 2D PIV method to determine the position of vortex breakdown point on a chined fuselage model is presented. In order to validate this criterion, the axial velocity of the vortex core is measured by Stereo PIV method on each cross section. An asymmetric angular configuration of two CCD cameras is applied to the Stereo PIV system, so that the particle images of Stereo PIV and 2D PIV results can be captured simultaneously. The results show that on the cross section of the vortex breakdown point, the axial velocity distribution across the vortex core shifts from the spray pattern to the wake pattern, leading to a sharp reduction of the axial velocity in the vortex core. Meanwhile the vorticity magnitude of the vortex core also decreases dramatically at the vortex breakdown point, caused by the abrupt diffuse of the vortex core and the sharp reduction of the circumferential velocity gradient. This characteristic can be used as a criterion to determine the position of vortex breakdown point.