Boundary streaming by internal waves

Damped internal wave beams in stratified fluids have long been known to generate strong mean flows through a mechanism analogous to acoustic streaming. While the role of viscous boundary layers in acoustic streaming has been thoroughly addressed, it remains largely unexplored in the case of internal...

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Bibliographic Details
Published in:Journal of fluid mechanics 2019-01, Vol.858, p.71-90
Main Authors: Renaud, A., Venaille, A.
Format: Article
Language:English
Subjects:
Acoustic streaming
Boundary conditions
Boundary layers
Boussinesq approximation
Boussinesq equations
Budgets
Computational fluid dynamics
Divergence
Fluid mechanics
Fluids
Gravitational waves
Interactions
Internal waves
JFM Papers
Laboratories
Mechanics
Oceans
Physics
Quasi-biennial oscillation
Reynolds number
Reynolds stress
Simulation
Streaming
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Summary:Damped internal wave beams in stratified fluids have long been known to generate strong mean flows through a mechanism analogous to acoustic streaming. While the role of viscous boundary layers in acoustic streaming has been thoroughly addressed, it remains largely unexplored in the case of internal waves. Here we compute the mean flow generated close to an undulating wall that emits internal waves in a viscous, linearly stratified two-dimensional Boussinesq fluid. Using a quasi-linear approach, we demonstrate that the form of the boundary conditions dramatically impacts the generated boundary streaming. In the no-slip scenario, the early-time Reynolds stress divergence within the viscous boundary layer is much stronger than within the bulk while also driving flow in the opposite direction. Whatever the boundary condition, boundary streaming is however dominated by bulk streaming at larger time. Using a Wentzel–Kramers–Brillouin approach, we investigate the consequences of adding boundary streaming effects to an idealised model of wave–mean flow interactions known to reproduce the salient features of the quasi-biennial oscillation. The presence of wave boundary layers has a quantitative impact on the flow reversals.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2018.786