Velocity and Density Determination by the Electron Beam Technique

Abstract

In aerothermodynamic gas flows the accurate knowledge of the velocity and the density is important as the Mach number is in the hypersonic range and relatively insensitive against real gas effects.This is true especially in the case of rarefied flows if the deviation of the continuum flow condition takes place, viscous effects have to be taken into account, and mixtures of gases have to be considered. In order to get access to these quantities the electron beam technique has been developed for space related research in the hypersonic wind tunnel of the institute. This paper summarizes the main features of the technique concerning density and veloctiy determination, typical experimental set-ups, results of some investigations, and advantages and drawbacks of the technique. Finally, as a new possibility for flow diagnostics an electron photon fluorescence technique using metastable atoms or molecules is discussed.