Leading-edge vortices due to low Reynolds number flow past a pitching delta wing

Flow past a pitching delta wing is examined in a water channel for a range of mean angle of attack. The wing is perturbed sinusoidally over a tenfold range of reduced frequency, in order to determine the nature of the vortex development and breakdown. There occur two basic types of vortex development: at low frequencies, the vortex core develops in the upstream direction towards the apex; at high frequencies, there is ejection of the leading edge of the vortex core from the apex in the downstream direction