Resection methodology for PSP data processing: Recent experiences in NAL

PSP data processing, which primarily involves image alignment and image analysis, is a crucial element in obtaining accurate PSP results. There are two broad approaches to image alignment: the algebraic transformation technique, often called image-warping technique, and resection methodology, which uses principles of optical photogrammetry. Resection is found to have higher resolution, especially when large gradients in pressure or significantly three-dimensional regions have to be resolved, and even with flat models when the camera angles are large. A processing software based on these methodologies has been successfully developed and validated and is currently in use at the Experimental Aerodynamics Division of the National Aerospace laboratories, Bangalore. In this paper, we show the merits of resection methodology through two examples: (a) a wing-body model in transonic flow (M = 0.8) and (b) a simple delta wing in low supersonic flow (M 1.8). The PSP system utilized for both the cases involve Optrod-B 1 paint, a specially designed UV lamp for excitation and two scientific grade CCD cameras for imaging. Typical results are shown using both the algebraic transformation approach and resection methodology.