CARS Measurement of Rotational and Vibrational Temperatures of Nitrogen Molecules in Nonequilibrium Flow behind Hypervelocity Shock Wave up to 7km/s

Abstract

In the present research the characteristics of nonequilibrium flow are studied by applying CARS (Coherent Anti-Stokes Raman Spectroscopy) method to hypervelocity shock waves in low-density air. Furthermore, in order to get more detail information on the flow behind the hypervelocity shock wave and to inspect whether the disturbance is seen at the shock wave front during the CARS measurement, radiation images behind the shock waves are obtained simultaneously. Finally, the CARS signals are detected behind hypersonic shock waves with a shock velocity of up to 7km/s. In addition, the radiation distributions are obtained at the same experiment. The vibrational and rotational temperatures are estimated by spectral fitting method. It is found that the rotational temperature exceeds the vibrational temperature when shock wave velocity is 5km/s or more, where both temperatures remains lower than translational temperature.