THE INTERACTION OF COHERENT VORTICES WITH SHORT FLAT PLATES

The interaction between a vortex and a small plate, are studied experi mentally in a water tunnel using a computer-controlled laser-Doppler v elocimeter. The interaction is proved to be a strong source of seconda ry and tertiary vorticity, the formation of which can be controlled by a selection of the plate dimensions, and cross-sectional shape. It is demonstrated that shorter plates with sharp edges are more efficient in breaking up oncoming vortical structures, while they create lower l evels of secondary and tertiary vorticity. Such devices could be emplo yed to control the amplitude of pressure fluctuations and the generati on of noise in many practical applications.