Visualization of high-speed flows at the peen state gas dynamics laboratory

Abstract

This paper reviews a variety of flow visualization techniques and non-intrusive optical diagnostics applied to high-speed viscous/inviscid flow interactions, and compressible vortices. These techniques, developed and applied in the Variable-Mach Number Supersonic Wind Tunnel Facility of the Penn State Gas Dynamics Laboratory, include holographic interferometry, laser light-screen imaging, high-speed schlieren photography, and a dry-transfer surface flow pattern method. Both qualitative and quantitative results are obtained from this array of flow visualization techniques, whose distinguishing characteristic is their ability to function without disturbing the airflow under observation. In particular, density differences which arise naturally in high-speed flows play a key role in our ability to observe such flows non-intrusively. Modern laser-based diagnostics, such as doubled-pulsed Ruby laser holographic interferometry, take advantage of such density differences in order to render visible the three-dimensional features of swept shock wave/boundary layer interactions. Mie scattering of the light from a thin Argon-ion laser sheet by moisture particles in the airflow reveals structural features of the flow at speeds up to Mach 4 in our test facility. A number of variations of the white-light schlieren technique also provide high-speed visualizations of shock wave structures, flow separation, and the strong interaction of a supersonic vortex with a shock wave.This paper reviews a variety of flow visualization techniques and non-intrusive optical diagnostics applied to high-speed viscous/inviscid flow interactions, and compressible vortices. These techniques, developed and applied in the Variable-Mach Number Supersonic Wind Tunnel Facility of the Penn State Gas Dynamics Laboratory, include holographic interferometry, laser light-screen imaging, high-speed schlieren photography, and a dry-transfer surface flow pattern method. Both qualitative and quantitative results are obtained from this array of flow visualization techniques, whose distinguishing characteristic is their ability to function without disturbing the airflow under observation. In particular, density differences which arise naturally in high-speed flows play a key role in our ability to observe such flows non-intrusively. Modern laser-based diagnostics, such as doubled-pulsed Ruby laser holographic interferometry, take advantage of such density differences in order to render visible the three-dimen...