“…Wang et al [23] generalized this model to moderately concentrated flows with additional modifications to the BGK operator. In terms of the way dealing with interparticle collisions, the Boltzmann operator [17,19] only applies for description of nearly elastic collisions, the revised Enskog theory (RET) becomes a unique alternative to describe collisions in considerably dissipative flow systems [24] , and the BGK operators preserve the essential properties of the Boltzmann and RET collisional operators. In contrast to difficulties in finding solutions to the Boltzmann equation and the RET theory equation, the BGK operators are simple in form facilitating analytical studies for practical applications.…”