Analysis of the physical nature of refractive index gradient in flow fields characterized with moiré tomography

In this study, the argon gas and argon arc plasma are chosen as two typical examples of cold and hot flow fields, respectively, to investigate on the physical nature of the refractive index gradient in moiré tomography diagnosis. The results indicate that refractive index gradient is mainly determined by refractive index sensitivity to the pressure change and the pressure gradient for the cold flow field. However, in the case of hot flows, refractive index gradient mainly depends on refractive index sensitivity to changes in pressure and temperature as well as to pressure and temperature gradients. The involved results can improve the use of moiré tomography for characterizing various complicated flow fields. This may extend the range of application of all methods that determine flow field's key parameters from refractive index distributions.