Windspeed and Flow Angle Measurement by Tracking of a Laser-Induced Breakdown Spark

摘要

An experimental measurement of three components of velocity and associated flow angles by optical tracking of the light emitted by a laser-induced breakdown (LIB) spark is described. The measurements were performed in a blowdown wind tunnel at a nominal flow Mach number of 4.38. The tests showed that flow velocity could be accurately measured using the technique, with a demonstrated flow-angle uncertainty of less than ± 0.2° at the Mach 4.38 test condition. Wavefront measurements through the shock of a 20° wedge were also performed, and indicated that the measurements could also be performed through a shock with negligible effect on spark formation due to the much smaller aperture of the LIB laser beam in relation to the wavelength of the shock aero-optical effect.