VISUALIZING VORTEX FORMATION IN THE WAKES OF TURBINE BLADES AND OSCILLATING AEROFOILS

摘要

Similarities between anomalous vortex shedding from blunt trailing-edged transonic turbine nozzle blades and from oscillating plunging aerofoils were investigated. Whereas under subsonic conditions the turbine nozzle cascade shed vortices in a conventional von Karman vortex-street wake, under transonic conditions a variety of different shedding configurations were observed with vortices shedding and pairing in different ways. Oscillating aerofoils were investigated in sinusoidal heaving motion in a water tunnel and a similar range of interesting wake vortex configurations was encountered. The established field of vortex-induced vibration has provided a developed classification scheme for the phenomena observed. The paper has brought together three previously unrelated fields of investigation and, by showing that the three are essentially related, has provided the basis for a new synthesis. The experiments were served well by the use of schlieren, including a novel use in conjunction with the hydraulic analogy, by the use of dye in a water tunnel and by computational work used to provide further interpretation of the observations.