title: Onsager's-principle-consistent 13-moment transport equations.
abstract: A new set of generalized transport equations is derived for higher-order moments which are generated in evolution equation for stress tensor and heat flux vector in 13-moment equations. The closure we employ satisfies Onsager's symmetry principle. In the derivation, we do not employ a phase density function based on Hermite polynomial series in terms of higher-order moments, unlike Grad's approach. The distribution function is rather chosen to satisfy collision invariance, and H-theorem and capture relatively strong deviations from equilibrium. The phase density function satisfies the linearized Boltzmann equation and provides the correct value of the Prandtl number for monatomic gas. The derived equations are compared with Grad's 13-moments equations for gas modeled as Maxwellian molecule. The merits of the proposed equations against Grad's and R13 equations are discussed. In particular, it is noted that the proposed equations contain higher-order terms compared to these equations but require a fewer number of boundary conditions as compared to the R13 equations. The Knudsen number envelope which can be covered to describe flows with these equations is therefore expected to be larger as compared to the earlier equations.
authors.affiliation: Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Narendra
authors.initials: N
authors.lastname: Singh
authors.affiliation: Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Agrawal