SBIR Phase II: A Multi-Point Array Laser Doppler Velocimeter

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AGRAWAL 9502488 This Small Business Innovation Research Phase-II project is directed at the completion of a research/commercial prototype multi-point laser velocimeter for use in laboratories and also for use unattended in the ocean. Measurements of velocity at a single point are seldom sufficient in nature; when only single-point velocimeters are available, profiling is employed to obtain information regarding structures of a flow-field. Profile information has invariably been derived by mechanical traversing of a sensor 'head'. Not only is synopticity sacrificed in this manner, causing loss of order in structure data, but also all information on spatial structures, coherent motions, and space-time scales is lost. Driven by needs in his research, the P.I. has devised a multi-point velocimetry system which forms several sample volumes in the flow field simultaneously. Signals from these sample volumes are separately carried to photo-detectors. A multi-signal processor is then required to convert the signal to simultaneous- multi-point velocity data, retaining information on order inherent in the flow, and all information for deriving space-time scales of fluid structures. In Phase-I, we have successfully demonstrated the principle of the method by constructing a single-velocity- component multi-point velocimeter, as first explained in the Phase- I proposal. In Phase-II, we shall expand capabilities to a 2-axis multi-point velocimeter, with direction discrimination optics and a complete multi-signal processor. The instrument will be tested in the laboratory and the field.