A Multi-Point Array Laser Doppler Velocimeter

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9361114 AGRAWAL We are proposing to develop a multi-point laser velocimeter to obtain velocities at a number of points, simultaneously and non- intrusively. Our specific interest is to apply this instrumentation to transport and exchange in surface and bottom boundary layers However, the technique will be applicable to a wide range of flows where simultaneous velocity measurements are desirable. At the heart of the innovation is a completely non- intrusive optical geometry which forms several sample volumes in the flow, and corresponding receiving optics to distinguish their images. Such a device is needed to observe structures in natural flows and to deal with issues such as flow stationarity. This simultaneous view of the velocity field will remove uncertainty in the interpretation of velocity profile information; e.g. the velocity shear and shear stress, turbulent characteristic scales and roughness lengths. The concept also concept also removes the need for mechanical scanning devices or profilers, both of which yield non-simultaneous measurements. The use of this instrument for characterizing the concentration and transport rate of sediments in the bottom boundary layer is described. The concept is also beneficial to laboratory scientists using flumes, towing tanks, and wind tunnels, in that multi-point measurements provide additional information on flow structure and improve productivity.