Planar Doppler Velocimetry System for High-Speed Flows

This is a proposal to develop a Planar Doppler Velocimetry (PDV) system for acquiring spatially- and temporally-resolved, three-component, velocity measurements around U.S. Air Force wind tunnel models, such as turrets and cavities, that have limited optical access. PDV is uniquely suited to flows in the transonic and supersonic regimes since the Doppler frequency shifts at these velocities are large and therefore easily measured. In addition, seed particles for the PDV technique can be small since they don¡¦t have to be individually resolved, so that light from a laser sheet placed in the field of interest is scattered relatively uniformly in all directions. Consequently, the imaging cameras can be placed anywhere within a wide range of possible locations, making this technique ideally suited for analyzing flow fields around such models. The proposed system would provide instantaneous planar velocity fields that include all three components. Each image may be acquired using either a conventional pulsed Nd:YAG laser to provide a large number of pulses for a statistically significant data set, or by using an optional burst-mode laser that will provide about 30 consecutive pulses at 4 ƒYs intervals for time resolved measurements.