Gas-phase velocimetry by nearly degenerate four-wave mixing

Abstract

We demonstrate a new velocimetry technique for gas flows based on Nearly Degenerate Four-Wave Mixing (NDFWM). Measurements were performed on nitric oxide in a free-jet expansion using helium and argon as carrier gases, at flow velocities on the order of 1000 m/s. We obtained velocities by analyzing experimental spectra from the jet using a perturbative treatment of NDFWM that we extended to include an arbitrary bulk velocity. The results agreed with independent velocity measurements based on Laser-Induced Fluorescence (LIF), as well as with theoretical flow-field velocities, to better than 5% in all cases studied.