Real-Time Background Oriented Schlieren Software Package Update, 2022(LEW-20407-1)

Background Oriented Schlieren (BOS) is an optical technique for measuring density gradients in flow fields, in quiescent air or even liquids. In traditional BOS, images of a speckled target are recorded using an electronic camera first at quiescent conditions (reference image) and then with the flow or density gradient causing phenomena initiated ('wind on' image). Small changes in the image of the speckled target caused by optical aberrations along the line-of-sight can be measured by cross-correlating the reference image with the 'wind on' image, yielding a map of the density gradients along the imaged path. The size of the speckles and their uniformity of illumination are critical to the success and sensitivity of the technique. BOS image data are recorded in real time using electronic CCD type cameras. However, processing and/or analysis of the traditional BOS image data is performed off-line after the test/experiment is completed.Advances in computer processing hardware enables the implementation of real-time processing and display of the BOS image data. Two different approaches to implementing the real-time BOS (RT-BOS) processing capability have been implemented. First, a traditional multicore Central Processing Unit (CPU) based approach using scheduled parallel threads is used to build a RT-BOS processing engine. In the second approach, a Graphical Processing Unit (GPU) approach is used to construct a RT-BOS processing engine. Generally, high-core count CPU processors can provide a useful processing rate for RT-BOS. However, the GPU based approach exceeds the processing capability of the CPU approach, at a fraction of the cost. The GPU approach places no restrictions on the host PC processing capability, except that it be capable of acquiring the BOS image data from the camera in real-time.