Wave boundary layers in rotating stratified fluid and near-inertial oscillations

2018 ◽  
Vol 68 (8) ◽  
pp. 987-1000 ◽  
Author(s):  
Gregory M. Reznik
2017 ◽  
Vol 833 ◽  
pp. 512-537 ◽  
Author(s):  
G. M. Reznik

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.


1967 ◽  
Vol 29 (1) ◽  
pp. 1-16 ◽  
Author(s):  
V. Barcilon ◽  
J. Pedlosky

A linear theory for steady motions in a rotating stratified fluid is presented, valid under the assumption that ε < E, where ε and E are respectively the Rossby and Ekman numbers. The fact that the stable stratification inhibits vertical motions has important consequences and many features of the dynamics of homogeneous rotating fluids are no longer present. For instance, in addition to the absence of the Taylor-Proudman constraint, it is found that Ekman layer suction no longer controls the interior dynamics. In fact, the Ekman layers themselves are frequently absent. Furthermore, the vertical Stewartson boundary layers are replaced by a new kind of boundary layer whose structure is characteristic of rotating stratified fluids. The interior dynamics are found to be controlled by dissipative processes.


2020 ◽  
Vol 9 (1) ◽  
pp. 27
Author(s):  
Hitoshi Tanaka ◽  
Nguyen Xuan Tinh ◽  
Xiping Yu ◽  
Guangwei Liu

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.


2019 ◽  
Vol 59 (2) ◽  
pp. 201-207
Author(s):  
G. M. Reznik

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.


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