On the Importance of High-Frequency Damping in High-Order Conservative Finite-Difference Schemes for Viscous Fluxes

TL;DR

This paper highlights the critical role of high-frequency damping in high-order conservative finite-difference schemes for viscous fluxes, demonstrating that appropriate damping resolves nonlinear instabilities and spurious oscillations in viscous flow simulations.

Contribution

It introduces a modified viscous scheme with a high-frequency damping term, improving stability and accuracy in high-order conservative finite-difference methods for viscous flows.

Findings

Adding high-frequency damping resolves spurious oscillations.

Modification improves stability in viscous shock simulations.

Damping is crucial in high-order conservative schemes.

Abstract

This paper discusses the importance of high-frequency damping in high-order conservative finite-difference schemes for viscous terms in the Navier-Stokes equations. Investigating nonlinear instability encountered in a high-resolution viscous shock-tube simulation, we have discovered that a modification to the viscous scheme rather than the inviscid scheme resolves a problem with spurious oscillations around shocks. The modification introduces a term responsible for high-frequency damping that is missing in a conservative high-order viscous scheme. The importance of damping has been known for schemes designed for unstructured grids. However, it has not been recognized well in very high-order difference schemes, especially in conservative difference schemes. Here, we discuss how it is easily missed in a conservative scheme and how to improve such schemes by a suitably designed damping term.