Skip to main content

Research Repository

Advanced Search

Layer formation and relaminarisation in plane Couette flow with spanwise stratification

Layer formation and relaminarisation in plane Couette flow with spanwise stratification Thumbnail


Abstract

In this paper we investigate the effect of stable stratification on plane Couette flow when gravity is oriented in the spanwise direction. When the flow is turbulent we observe near-wall layering and associated new mean flows in the form of large-scale spanwise-flattened streamwise rolls. The layers exhibit the expected buoyancy scaling where U is a typical horizontal velocity scale and lz ~ U / N the buoyancy frequency. We associate the new coherent structures with a stratified modification of the well-known large-scale secondary circulation in plane Couette flow. We find that the possibility of the transition to sustained turbulence is controlled by the relative size of this buoyancy scale to the spanwise spacing of the streaks. In parts of parameter space transition can also be initiated by a newly discovered linear instability in this system (Facchini et al., J. Fluid Mech., vol. 853, 2018, pp. 205–234). When wall turbulence can be sustained the linear instability opens up new routes in phase space for infinitesimal disturbances to initiate turbulence. When the buoyancy scale suppresses turbulence the linear instability leads to more ordered nonlinear states, with the possibility for intermittent bursts of secondary shear instability.

Acceptance Date Feb 27, 2019
Publication Date Jun 10, 2019
Publicly Available Date Mar 28, 2024
Journal Journal of Fluid Mechanics
Print ISSN 0022-1120
Publisher Cambridge University Press
Pages 97-118
DOI https://doi.org/10.1017/jfm.2019.192
Keywords mathematical sciences, engineering
Publisher URL https://doi.org/10.1017/jfm.2019.192

Files




Downloadable Citations