Hypersonic application of focused schlieren and deflectometry.

摘要

A non-intrusive diagnostic capability for determining the hypersonic shock and boundary layer structure was developed, installed, and successfully tested at the AEDC Hypervelocity Tunnel 9. This customized diagnostic involves a combination of a focused schlieren system, which relies on creating multiple virtual light sources using a Fresnel lens and a source grid, and a deflectometry system, which uses the focused schlieren and a photomultiplier tube. It was used for obtaining spatially resolved images of density gradients with a depth of focus less than one centimeter, while allowing high frequency measurements of density fluctuations. The diagnostic was applied in investigating the second mode instability waves present in the boundary layer of a sharp-nosed cone submerged in a Mach 10 flow. The waves were successfully imaged and their frequencies were measured even though the flow density was below 0.01 kgm3 and the frequencies over 200 kHz. This adds a new capability to hypersonic testing.