Capturing nongradient transport in nonequilibrium gas flow

A higher order moment method is employed to construct the transport model for nonequilibrium gas flow in microscale geometries. The one dimensional planar Couette flow was chosen to demonstrate the significance of capturing the nongradient transport phenomena in the prediction of velocity and temperature fields. For planar Couette flow in the transition regime, the velocity profile is nonlinear and the induced temperature field is no longer parabolic. These features are attributed to the nongradient transport mechanism in a nonequilibrium gas. Furthermore, it is revealed that, for a given temperature field, the gradient transport model overestimates the heat transfer significantly. This, again, can be compensated by the nongradient transport mechanism.