Comment on "Physical significance of artificial numerical noise in direct numerical simulation of turbulence"

Abstract

Recently, Liao and Qin [J. Fluid Mech. 1008, R2 (2025)] claimed that numerical noise in direct numerical simulation of turbulence using the deterministic Navier-Stokes equations is "approximately equivalent" to the physical noise arising from random molecular motion (thermal fluctuations). We show here that it this claim not supported by their results and that it contradicts other results in the literature. Furthermore, we demonstrate that the numerical implementation of thermal fluctuations in their so-called "clean numerical simulations" is incorrect.