Fluorescence imaging and streakline visualization of hypersonic flow over rapid prototype wind-tunnel models

Abstract

The use of planar laser-induced fluorescence (PLIF) of nitric oxide (NO) was inves-tigated for use in visualizing wake flowfields downstream of rapid prototyping models in a hypersonic wind tunnel. The re-entry models for use in this study were fabricated using a stereo-lithography apparatus. These models were produced in one day or less, which is a significant time savings compared with the manufacture of ceramic or metal models. The models were tested in the NASA Langley Research Center 31-Inch Mach 10 Air Tunnel. Pure NO was either seeded through tubes plumbed into the model or via a tube attached to the strut holding the model, which provided localized addition of NO into the model's wake through a porous metal cylinder attached to the end of the tube. Various entry capsule model types and configurations and NO-seeding methods were used, including a new streamwise visualization method based on PLIF. Virtual diagnostics interface technology, developed at NASA Langley Research Center, was used to visualize the datasets in post-processing. The use of calibration ‘dotcards’ was investigated to correct for camera perspective and lens distortions in the PLIF images.