Three-component phase-averaged velocitymeasurements of an optically perturbed supersonicjet using multi-component planar Doppler velocimetry

Abstract

In the planar Doppler velocimetry (PDV) technique, a molecular/atomicfilter is employed to convert frequency shifts in scattered light to intensityvariations. The potential for instantaneous three-component velocitymeasurements over an entire laser sheet makes PDV attractive for use in largewind tunnels. The development and integration of hardware and software fordeployment of a multi-component PDV system is reported. Hardware issuesaddressed include observation of the long-term stability of a starved iodinecell. In addition, the accuracy of the dot-locating scheme, essential in the PDVdata-reduction process, is investigated using numerically generated images.Finally, operation of a two-component system is demonstrated with velocitymeasurements in a supersonic jet with a large-scale perturbation. Here, energyfrom a Nd:YAG laser is focused into the shear layer near the lip of the nozzleto create a small thermal spot. The PDV technique is then employed to study theevolution of the large-scale disturbance. Two orientations of the two-componentvelocity measurement system are used to produce phase-averaged three-componentmean velocity measurements of the perturbed jet 170 and 220 µs after theintroduction of the disturbance.