Small Rarefaction, Large Consequences: Limits of Navier Stokes Turbulence Simulations

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Hauptverfasser: Tian, Songyan, Wu, Lei
Format: Preprint
Veröffentlicht: 2026
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author Tian, Songyan
Wu, Lei
author_facet Tian, Songyan
Wu, Lei
contents We conduct numerical simulations of rocket plume impingement on a lunar landing surface using two complementary frameworks: the Boltzmann equation, which naturally captures rarefied gas dynamics, and the Navier Stokes (NS) equations, the conventional workhorse for turbulent flow simulations. We show that subtle rarefaction effects, long considered negligible in turbulent regimes, can become locally dominant within shear layers where viscous stresses predicted by the NS constitutive relation undergo sign reversals. This phenomenon, which we term constitutive degeneracy, produces order-one relative errors in predicted surface shear stress and heat flux. Our results demonstrate that turbulence can expose hidden limits of NS equations with broad implications for high-speed aerodynamics and planetary exploration.
format Preprint
id arxiv_https___arxiv_org_abs_2602_08770
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Small Rarefaction, Large Consequences: Limits of Navier Stokes Turbulence Simulations
Tian, Songyan
Wu, Lei
Fluid Dynamics
We conduct numerical simulations of rocket plume impingement on a lunar landing surface using two complementary frameworks: the Boltzmann equation, which naturally captures rarefied gas dynamics, and the Navier Stokes (NS) equations, the conventional workhorse for turbulent flow simulations. We show that subtle rarefaction effects, long considered negligible in turbulent regimes, can become locally dominant within shear layers where viscous stresses predicted by the NS constitutive relation undergo sign reversals. This phenomenon, which we term constitutive degeneracy, produces order-one relative errors in predicted surface shear stress and heat flux. Our results demonstrate that turbulence can expose hidden limits of NS equations with broad implications for high-speed aerodynamics and planetary exploration.
title Small Rarefaction, Large Consequences: Limits of Navier Stokes Turbulence Simulations
topic Fluid Dynamics
url https://arxiv.org/abs/2602.08770