Measurement of Shock Wave Thickness by the Electron Beam Fluorescence Method

摘要

Shock wave thicknesses and density ratios were measured in helium, argon and nitrogen by means of the electron beam fluorescence method, over the range 1.5 less than M less than 17.4, in a low density wind tunnel. The shock thicknesses in argon and helium agreed well with Mott-Smith theory at the higher Mach numbers, and were between Navier-Stokes and Mott-Smith theory at the lowest Mach number. In nitrogen, the measured shock thicknesses were considerably greater than the predictions of Navier-Stokes theory. Measured density ratios across the shock wave were in good agreement with theory, in the lower density flows. Poorer agreement was found at higher flow densities, leading to estimates of upper bounds for the range of linear variation of fluorescence intensity with gas density. Measured density ratios for shocks produced in divergent free-jet flows were found to be in better agreement with theory after a viscous curvature correction was applied. (Author)