AIAA 98–2703 PLIF Thermometry of a Free-Piston Shock-Tunnel Nozzle Flow

Planar Laser-Induced Fluorescence PLIF is employed to measure rotational temperatures at the nozzle exit of a free-piston shock tunnel. The ow is at approximately Mach 7 and chemical eeects have been reduced by using a nitrogen test gas and low total enthalpy 5 MJJkg. Vibrational freezing in the nozzle expansion has an appreciable effect on the nozzle-exit rotational temperature, and therefore the measurements are used to verify vibrational freezing models. Two computer codes are used for modelling the ow: a quasi-one dimensional nozzle ow code STUBE, and a two dimensional blahh blahh code called blahh. The results indicate reasonable agreement b e t w een theory and experiment, but further work is required to identify the exact source of descrepancies. The PLIF technique is identiied as an excellent tool for visualising ow non-uniformities and measuring temperatures. In particular, the early arrival of driver gas, which can cause signiicant measurement errors, was observed.