Numerical Bow Shock Instabilities in Inert Polyatomic Gases

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Hauptverfasser: Sidharth, G. S., Dwivedi, Anubhav
Format: Preprint
Veröffentlicht: 2026
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author Sidharth, G. S.
Dwivedi, Anubhav
author_facet Sidharth, G. S.
Dwivedi, Anubhav
contents We investigate inviscid numerical instabilities that arise in simulations of axisymmetric flow over a hypersonic sphere in an inert, calorically perfect gas at low specific heat ratio ($γ\approx 1.1$--$1.2$). We show that when the density ratio across the bow shock is high and the computational mesh is relatively coarse, numerically induced traveling-wave instabilities of the carbuncle type can develop in the shock layer near stagnation for inert gases. These instabilities, not previously documented in the literature, are noteworthy because bow shock oscillations are also observed experimentally in polyatomic gases exhibiting post-shock thermochemical relaxation. When such gases are modeled as inert with an effectively low $γ$, our results emphasize the need for caution to avoid conflating genuine physical instabilities with numerical artifacts in simulations.
format Preprint
id arxiv_https___arxiv_org_abs_2604_00577
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Numerical Bow Shock Instabilities in Inert Polyatomic Gases
Sidharth, G. S.
Dwivedi, Anubhav
Fluid Dynamics
Computational Physics
We investigate inviscid numerical instabilities that arise in simulations of axisymmetric flow over a hypersonic sphere in an inert, calorically perfect gas at low specific heat ratio ($γ\approx 1.1$--$1.2$). We show that when the density ratio across the bow shock is high and the computational mesh is relatively coarse, numerically induced traveling-wave instabilities of the carbuncle type can develop in the shock layer near stagnation for inert gases. These instabilities, not previously documented in the literature, are noteworthy because bow shock oscillations are also observed experimentally in polyatomic gases exhibiting post-shock thermochemical relaxation. When such gases are modeled as inert with an effectively low $γ$, our results emphasize the need for caution to avoid conflating genuine physical instabilities with numerical artifacts in simulations.
title Numerical Bow Shock Instabilities in Inert Polyatomic Gases
topic Fluid Dynamics
Computational Physics
url https://arxiv.org/abs/2604.00577