Exact nonlocal hydrodynamics predict rarefaction effects.

Kogelbauer, Florian; Karlin, Ilya · Phys Rev E · 2025

basic_science · Level V

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Abstract

We combine the theory of slow spectral closure for linearized Boltzmann equations with Maxwell's kinetic boundary conditions to derive optimal hydrodynamics with arbitrary accommodation. Focusing on shear-mode dynamics, we obtain explicit steady state solutions in terms of Fourier integrals and closed-form expressions for the mean flow and the stress. We demonstrate that the exact nonlocal fluid model correctly predicts several rarefaction effects with accommodation, including the Couette flow and thermal creep in a plane channel.