Non‐Negligible Influence of Forcing Mechanisms on Turbulent Mixing at Low Reynolds Numbers: A One‐Dimensional Turbulence Study

Source abstract

ABSTRACT This study presents a numerical investigation of passive scalar mixing in homogeneous isotropic turbulence (HIT). Different volumetric forcing schemes have been used in the literature, but the side effects are rarely discussed, either because these are assumed irrelevant or because it is too costly to conduct such an analysis with a high‐fidelity model. In this study, we have used One‐Dimensional Turbulence (ODT) model to compare forcing schemes at low Reynolds numbers (upto ). Our analysis reveals critical flaws in the linear forcing model when applied to ODT. While both schemes exhibit spectral deviations from direct numerical simulation (DNS), the stochastic forcing scheme demonstrates superior dynamic fidelity, better capturing the turbulent energy cascade. In contrast, the linear forcing scheme suffers from a non‐physical energy deficit at large scales and is approximately 10 times more computationally expensive. These artefacts directly impact scalar mixing: The stochastic scheme produces classic, multi‐scale intermittency, whereas linear forcing generates extreme gradients confined only at the dissipative scales. These results demonstrate that the choice of forcing is a critical modelling decision in ODT, leading to fundamentally different model‐dependent artefacts in both turbulence dynamics and scalar mixing statistics, at least in low Reynolds number regimes.