Planar Fluorescence Imaging and Three-Dimensional Reconstructions of Capsule Reaction-Control-System Jets

Planar laser-induced-fluorescence flowfield visualization has been used to investigate reaction-control-system jet flows in the wake of hypersonic capsule reentry vehicles. Pitch, roll, and yaw reaction-control-system jets were all studied. Planar laser-induced fluorescence was used to obtain offbody flow images at planar slices in these flowfields, which are not easily visualized by other techniques, owing to characteristically low gas density. When viewed individually, these slices are shown to provide spatially and temporally resolved information, including the locations and characteristics of turbulent flow structures and the location of the jet flow relative to the vehicle. In addition, ensembles of slices acquired at multiple locations throughout the flowfield are combined using computer visualization techniques to reconstruct the three-dimensional shape of the flow. Collectively, the offbody flow-visualization data set acquired in these tests represents a valuable complement to surface measurements, especially as a basis for explaining otherwise perplexing discrepancies between such measurements and computational fluid dynamics results. The tests described herein were conducted in the 31-Inch Mach 10 Air Tunnel at NASA Langley Research Center.

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