An Experimental Investigation of Vortex Rings and Helicopter Rotor Wakes Using a Laser Doppler Velocimeter.

摘要

The report describes a laser Doppler velocimeter (LDV) capable of performing measurements in vortex cores,presents detailed measurements of structure and stability of vortex rings and also presents measurements in the wake of a model helicopter rotor. The use of conventional instrumentation such as hot wire anemometer for measuring velocity in vortex filament is hampered by probe interference and the difficulty of calibrating the probe in a flow field where the velocity is changing rapidly in magnitude and direction. For these reasons, a laser Doppler velocimeter (LDV) is used throughout these experiments. The LDV measures the velocity of smoke particles by measuring the Doppler shift of laser light scattered from the particles. (Modified author abstract)