"Visualization of Vortex-Wing Interactions"

Speaker: Donald Rockwell, Lehigh University, USA

The overall aim of the investigations described in this presentation is to gain insight into the quantitative flow physics of trailing vortex- wing interactions. Stereo particle image velocimetry leads to volume representations of the flow structure for nominally stationary and undulating vortices. Sectional cuts of the distorted vortex along the wing are classified according to critical points of the streamline topology in relation to concentrations of vorticity. For the case of a perturbed trailing vortex evolving in absence of a downstream wing, the relationship between velocity defect, axial vorticity, swirl ratio and azimuthal vorticity is characterized along the undulating vortex for both unidirectional and orbital motion. When either a perturbed or unperturbed trailing vortex is incident upon a downstream wing, distinctive elements of the flow structure are highly sensitive to small variations of the offset of the incident vortex relative to the tip of the wing; these elements can be modified substantially by small amplitude vibrations of the downstream wing.