On the accuracy of two temperature models for hypersonic nonequilibrium flow

Due to the empirical assumptions, the widely used two temperature models for hypersonic nonequilibrium flow include considerable uncertainties. To overcome the limitations and shortcomings of two temperature models, the modified Macheret Fridman model is developed based on the correction method of the modified Marrone Treanor model. Some typical test cases are employed to assess the accuracy of the modified and widely used two temperature models. Furthermore, the reason for improving the accuracy of modified two temperature models is analyzed and discussed. This work indicates that the correction method based on the modified Marrone Treanor model is easily applied and extended to the other widely used two temperature models, significantly improving their accuracy. In addition, modeling highly nonequilibrium dissociating flows requires considering three critical respects, i.e., the dissociation rates, the vibration dissociation coupling effect, and the non Boltzmann effect. The non Boltzmann effect reduces the dissociation rates and vibrational energy per dissociation. Comparatively, the dissociation rates have more influence than changing the value of the non Boltzmann factor for vibrational energy loss per dissociation. Future work can focus on enhancing the accuracy of the dissociation rates to improve the accuracy of widely used two temperature models.