Development of a Novel Optical Flow Diagnostic Technique for Simultaneous Measurement of Velocity and Density in Fluid Flow with Density Gradients

The objective of this project was to develop a seedless velocimetry technique to obtain velocity fields in heated flows, which pose a challenge for seeding. The approach used here is to use the Background Oriented Schlieren (BOS - also developed at NAL) to track density features as a marker to reveal the flow features, which are then correlated and their local velocities measured thus forming a basis of Seedless Image Velocimetry. Seedless Image Velocimetry is shown to yield valid velocimetry data, within certain limits, for an axisymmetric turbulent heated plume jet in air. Due to the line of sight integration in the plume, the FBPT algorithm developed for the BOS is used to extract center-plane velocity data. While not useful for laminar or fully 3D flows, it nevertheless has significant promise. Despite its limitations, the method shows promise as a new optical velocimetry tool. Further work is required to optimize the hardware and the analysis software in order to make it a fully implementable tool