Work

Ordering of time scales predicts applicability of quasilinear theory in unstable flows

Year: 2024

Type: article

Abstract: We discuss the applicability of quasilinear-type approximations for a turbulent system with a large range of spatial and temporal scales. We consider a paradigm fluid system of rotating convection with vertical and horizontal temperature gradients. In particular, the interaction of rotation with the horizontal temperature gradient drives a ‘thermal wind’ shear flow whose strength is controlled by the horizontal temperature gradient. Varying this parameter therefore systematically alters the ordering of the shearing time scale, the convective time scale and the correlation time scale. We demonstrate that quasilinear-type approximations work well when the shearing time scale or the correlation time scale is sufficiently short. In all cases, the generalised quasilinear approximation systematically outperforms the quasilinear approximation. We discuss the consequences for statistical theories of turbulence interacting with mean gradients.

Source: Journal of Fluid Mechanics

DOI: 10.1017/jfm.2024.810

Authors: Curtis J. Saxton, J.B. Marston, Jeffrey S. Oishi, Steven M. Tobias

Institutions: University of Warwick, Brown University, University of Leeds

Language: English

Topic: Fluid Dynamics and Turbulent Flows

Subfield: Computational Mechanics

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,450

Funders: National Aeronautics and Space Administration, University of Leeds, European Commission, H2020 European Research Council