An Experimental Analysis of Vortex Trapping Techniques

Abstract

An experimental verification is presented for the theoretical vortex trapping concept. A suction orifice located along one wall of a water channel test section was used to simulate a point sink to trap spanwise vortices downstream of a backward-facing step and between two parallel fences. Results from the backward-facing step geometry indicated an increase in the sink strength required to hold a vortex as the sink is positioned closer to the step, closely following previous theoretical predictions made using conformal mapping. The experimental data also showed reasonable agreement with the theoretical position for optimum vortex trapping. Flow visualization has shown a three-dimensional cross-stream effect due to bending of the forced-vortex core by suction. Results from the dual-fence geometry, on the other hand, verified the ability to use a lower level of suction for vortex trapping when compared with the backward-facing step.