Inconsistency between the micropolar theory and non-equilibrium thermodynamics in the case of polar fluids

The balance equation of angular momentum in anisotropic fluids includes a couple stress contribution, also responsible for an antisymmetric contribution to the force stress tensor. We herein derive all balance equations for the simplest anisotropic fluid, i.e., a polar fluid, using the GENERIC formalism of non-equilibrium thermodynamics. In doing so, we find that there is an inconsistency between the internal energy density evolution equation derived using non-equilibrium thermodynamics and the one usually considered in micropolar theory.