scholarly journals Wave boundary layers in a stably-neutrally stratified ocean

2019 ◽  
Vol 59 (2) ◽  
pp. 201-207
Author(s):  
G. M. Reznik
Keyword(s):  
Boundary Layer ◽  
Asymptotic Solution ◽  
Boundary Layers ◽  
Ocean Bottom ◽  
Linear Evolution ◽  
Term Evolution ◽  
Stratified Ocean ◽  
Wave Boundary ◽  
Neutrally Stratified

The theory of wave boundary layers developed in [7], is generalized to the case of stably-neutrally stratified ocean consisting of upper homogeneous and lower stratified layers. In this configuration, in addition to the boundary layers near the ocean bottom and/or surface, a wave boundary layer develops near the interface between the layers in the lower stratified part of basin. Each the boundary layer is a narrow domain characterized by sharp, growing in time, vertical gradients of buoyancy and horizontal velocity. As in [7], the near interface boundary layer arises as a result of free linear evolution of rather general initial fields. An asymptotic solution describing the long-term evolution is presented and compared to exact solution; the asymptotic solution approximates the exact one fairly well even on not very large times.

scholarly journals Development of Depth-Limited Wave Boundary Layers over a Smooth Bottom

2020 ◽  
Vol 9 (1) ◽  
pp. 27
Author(s):  
Hitoshi Tanaka ◽  
Nguyen Xuan Tinh ◽  
Xiping Yu ◽  
Guangwei Liu
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Boundary Layers ◽  
Wave Motion ◽  
Numerical Study ◽  
Experiment Data ◽  
Tidal Motion ◽  
Long Period ◽  
Simulation Results ◽  
Wave Boundary

A theoretical and numerical study is carried out to investigate the transformation of the wave boundary layer from non-depth-limited (wave-like boundary layer) to depth-limited one (current-like boundary layer) over a smooth bottom. A long period of wave motion is not sufficient to induce depth-limited properties, although it has simply been assumed in various situations under long waves, such as tsunami and tidal currents. Four criteria are obtained theoretically for recognizing the inception of the depth-limited condition under waves. To validate the theoretical criteria, numerical simulation results using a turbulence model as well as laboratory experiment data are employed. In addition, typical field situations induced by tidal motion and tsunami are discussed to show the usefulness of the proposed criteria.

scholarly journals Turning Ocean Mixing Upside Down

2016 ◽  
Vol 46 (7) ◽  
pp. 2239-2261 ◽  
Author(s):  
Raffaele Ferrari ◽  
Ali Mashayek ◽  
Trevor J. McDougall ◽  
Maxim Nikurashin ◽  
Jean-Michael Campin
Keyword(s):  
Boundary Layers ◽  
Numerical Models ◽  
Meridional Overturning Circulation ◽  
Small Scale ◽  
Ocean Bottom ◽  
Overturning Circulation ◽  
Bottom Boundary ◽  
Bottom Boundary Layers ◽  
Meridional Overturning ◽  
Stratified Ocean

AbstractIt is generally understood that small-scale mixing, such as is caused by breaking internal waves, drives upwelling of the densest ocean waters that sink to the ocean bottom at high latitudes. However, the observational evidence that the strong turbulent fluxes generated by small-scale mixing in the stratified ocean interior are more vigorous close to the ocean bottom boundary than above implies that small-scale mixing converts light waters into denser ones, thus driving a net sinking of abyssal waters. Using a combination of theoretical ideas and numerical models, it is argued that abyssal waters upwell along weakly stratified boundary layers, where small-scale mixing of density decreases to zero to satisfy the no density flux condition at the ocean bottom. The abyssal ocean meridional overturning circulation is the small residual of a large net sinking of waters, driven by small-scale mixing in the stratified interior above the bottom boundary layers, and a slightly larger net upwelling, driven by the decay of small-scale mixing in the boundary layers. The crucial importance of upwelling along boundary layers in closing the abyssal overturning circulation is the main finding of this work.

scholarly journals Long-term evolution and coupling of the boundary layers in the Stratus Deck Regions of the eastern Pacific (STRATUS)

2001 ◽  
Author(s):  
Lisanne E. Lucas ◽  
Bryan S. Way ◽  
Robert A. Weller ◽  
Paul R. Bouchard ◽  
Albert S. Fischer ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Long Term Evolution ◽  
Eastern Pacific ◽  
Term Evolution

Wave boundary layers in a stratified fluid

2017 ◽  
Vol 833 ◽  
pp. 512-537 ◽  
Author(s):  
G. M. Reznik
Keyword(s):  
Exact Solutions ◽  
Boundary Layers ◽  
Vertical Velocity ◽  
Velocity Gradient ◽  
Initial Perturbation ◽  
Stratified Fluid ◽  
Horizontal Velocity ◽  
Asymptotic Solutions ◽  
Linear Evolution ◽  
Wave Boundary

We study so-called wave boundary layers (BLs) arising in a stably stratified fluid at large times. The BL is a narrow domain near the surface and/or bottom of the fluid; with increasing time, gradients of buoyancy and horizontal velocity in the BL grow sharply and the BL thickness tends to zero. The non-stationary BL can arise both as a result of linear evolution of the initial perturbation and under the action of an external force (tangential stress exerted on the fluid surface in our case). We analyse both the variants and find that the ‘forced’ BLs are much more intense than the ‘free’ ones. In the ‘free’ BLs all fields are bounded and the gradients of buoyancy and horizontal velocity grow linearly in time, whereas in the ‘forced’ BL only the vertical velocity is bounded and the buoyancy and horizontal velocity grow linearly in time. As to the gradients in the ‘forced’ BL, the vertical velocity gradient grows in time linearly and the gradients of buoyancy and horizontal velocity grow quadratically. In both of the cases we determine exact solutions in the form of expansions in the vertical wave modes and find asymptotic solutions valid at large times. The comparison between them shows that the asymptotic solutions approximate the exact ones fairly well even for moderate times.

Coherent structures in wave boundary layers. Part 2. Solitary motion

2010 ◽  
Vol 646 ◽  
pp. 207-231 ◽  
Author(s):  
B. MUTLU SUMER ◽  
PALLE M. JENSEN ◽  
LONE B. SØRENSEN ◽  
JØRGEN FREDSØE ◽  
PHILIP L.-F. LIU ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Boundary Layers ◽  
Bed Shear Stress ◽  
Laminar Regime ◽  
Short Period ◽  
Flow Features ◽  
Layer Flow ◽  
Wave Boundary ◽  
Flow Experiences

This study continues the investigation of wave boundary layers reported by Carstensen, Sumer & Fredsøe (J. Fluid Mech., 2010, part 1 of this paper). The present paper summarizes the results of an experimental investigation of turbulent solitary wave boundary layers, simulated by solitary motion in an oscillating water tunnel. Two kinds of measurements were made: bed shear stress measurements and velocity measurements. The experiments show that the solitary-motion boundary layer experiences three kinds of flow regimes as the Reynolds number is increased: (i) laminar regime; (ii) laminar regime where the boundary-layer flow experiences a regular array of vortex tubes near the bed over a short period of time during the deceleration stage; and (iii) transitional regime characterized with turbulent spots, revealed by single/multiple, or, sometimes, quite dense spikes in the bed shear stress traces. Supplementary synchronized flow visualization tests confirmed the presence of the previously mentioned flow features. Information related to flow resistance are also given in the paper.

scholarly journals Long-term evolution of the coupled boundary layers (Stratus) mooring recovery and deployment cruise report R/V Melville

2003 ◽  
Author(s):  
Lara Hutto ◽  
Robert Weller ◽  
Jeff Lord ◽  
Jim Ryder ◽  
Alice Stuart-Menteth ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Long Term Evolution ◽  
Term Evolution

scholarly journals Dynamics of an Abyssal Circulation Driven by Bottom-Intensified Mixing on Slopes

2018 ◽  
Vol 48 (6) ◽  
pp. 1257-1282 ◽  
Author(s):  
Jörn Callies ◽  
Raffaele Ferrari
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Large Scale ◽  
Boundary Layer Theory ◽  
Internal Tides ◽  
Small Scale ◽  
Ocean Bottom ◽  
Basin Scale ◽  
Lee Waves ◽  
Abyssal Circulation

AbstractThe large-scale circulation of the abyssal ocean is enabled by small-scale diapycnal mixing, which observations suggest is strongly enhanced toward the ocean bottom, where the breaking of internal tides and lee waves is most vigorous. As discussed recently, bottom-intensified mixing induces a pattern of near-bottom up- and downwelling that is quite different from the traditionally assumed widespread upwelling. Here the consequences of bottom-intensified mixing for the horizontal circulation of the abyssal ocean are explored by considering planetary geostrophic dynamics in an idealized “bathtub geometry.” Up- and downwelling layers develop on bottom slopes as expected, and these layers are well described by boundary layer theory. The basin-scale circulation is driven by flows in and out of these boundary layers at the base of the sloping topography, which creates primarily zonal currents in the interior and a net meridional exchange along western boundaries. The rate of the net overturning is controlled by the up- and downslope transports in boundary layers on slopes and can be predicted with boundary layer theory.

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