Revisit to Grad's Closure and Development of Physically Motivated Closure for Phenomenological High-Order Moment Model

Abstract

The Grad's closure for the high-order moment equation is revisited and, by extending his theory, a physically motivated closure is developed for the one-dimensional velocity shear gas flow. The closure is based on the physical argument of the relative importance of various terms appearing in the moment equation. Also, the closure is derived such that the resulting theory may be inclusive of the well established linear theory (Navier- Stokes-Fourier) as limiting case near local thermal equilibrium.