On mean flow generation due to oblique reflection of internal waves at a slope

2019 ◽  
Vol 142 (4) ◽  
pp. 419-432 ◽  
Author(s):  
Takeshi Kataoka ◽  
T. R. Akylas
Keyword(s):  
Internal Waves ◽  
Mean Flow ◽  
Oblique Reflection ◽  
Flow Generation

Interaction of internal waves and mean flow observed near a coast

1988 ◽  
Vol 46 (1) ◽  
pp. 1-23 ◽  
Author(s):  
Pijush K. Kundu ◽  
Richard E. Thomson ◽  
Barbara M. Hickey ◽  
Paul H. LeBlond
Keyword(s):  
Internal Waves ◽  
Mean Flow

Mean flow generation along a sloping region in a rotating homogeneous fluid

1996 ◽  
Vol 101 (C12) ◽  
pp. 28597-28614 ◽  
Author(s):  
Xiuzhang Zhang ◽  
Don L. Boyer ◽  
Nicolas Pérenne ◽  
Dominique P. Renouard
Keyword(s):  
Mean Flow ◽  
Homogeneous Fluid ◽  
Flow Generation

scholarly journals Streaming by leaky surface acoustic waves

2010 ◽  
Vol 467 (2130) ◽  
pp. 1779-1800 ◽  
Author(s):  
J. Vanneste ◽  
O. Bühler
Keyword(s):  
Surface Waves ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Acoustic Streaming ◽  
Stokes Drift ◽  
Mean Flow ◽  
Matched Asymptotics ◽  
Flow Generation ◽  
Solid Liquid Interface ◽  
Solid Liquid

Acoustic streaming, the generation of mean flow by dissipating acoustic waves, provides a promising method for flow pumping in microfluidic devices. In recent years, several groups have been experimenting with acoustic streaming induced by leaky surface waves: (Rayleigh) surface waves excited in a piezoelectric solid interact with a small volume of fluid where they generate acoustic waves and, as result of the viscous dissipation of these waves, a mean flow. We discuss the computation of the corresponding Lagrangian mean flow, which controls the trajectories of fluid particles and hence the mixing properties of the flows generated by this method. The problem is formulated using the averaged vorticity equation which extracts the dominant balance between wave dissipation and mean-flow dissipation. Particular attention is paid to the thin boundary layer that forms at the solid/liquid interface, where the flow is best computed using matched asymptotics. This leads to an explicit expression for a slip velocity, which includes the effect of the oscillations of the boundary. The Lagrangian mean flow is naturally separated into three contributions: an interior-driven Eulerian mean flow, a boundary-driven Eulerian mean flow and the Stokes drift. A scale analysis indicates that the latter two contributions can be neglected in devices much larger than the acoustic wavelength but need to be taken into account in smaller devices. A simple two-dimensional model of mean flow generation by surface acoustic waves is discussed as an illustration.

On internal waves generated by travelling wind

1993 ◽  
Vol 254 ◽  
pp. 529-559 ◽  
Author(s):  
Pijush K. Kundu
Keyword(s):  
Surface Layer ◽  
Internal Waves ◽  
Large Fraction ◽  
Deep Ocean ◽  
Buoyancy Frequency ◽  
Vertical Acceleration ◽  
Mean Flow ◽  
Moving Line ◽  
Vertical Correlation ◽  
Low Order

Oceanic internal waves forced by a latitude-independent wind field travelling eastward at speed U is investigated, extending the hydrostatic f-plane model of Kundu & Thomson (1985). The ocean has a well-mixed surface layer overlying a stratified interior with a depth-dependent buoyancy frequency N(z), and f can vary with latitude. Solutions are found by decomposition into vertical normal modes. Problems discussed are (i) the response to a slowly moving line front, and (ii) the response in a variable f ocean.For the slowly moving line front assuming a depth-independent N, the trailing waves are found to have large frequencies, and the vertical acceleration ∂w/∂t is important (that is the dynamics are non-hydrostatic) if the frequency ω is larger than a few times (Nf)½. The wake contains waves associated with all vertical modes, in contrast to hydrostatic dynamics in which slowly moving line fronts do not generate trailing waves of low-order modes. It is argued that slowly moving wind fields can provide an explanation for the frequently observed broad peak in the spectrum of vertical motion at a frequency somewhat smaller than N, and of the vertical coherence of the associated waves in the upper ocean.To study lower-frequency internal waves, the hydrostatic constant-f model of Kundu & Thomson is extended to variable f. Various sections through such a flow clearly illustrate the development of a meridional wavelength λy = 2π/βt as predicted by D'Asaro (1989), in addition to the zonal wavelength λx due to translation of the wind. The two effects combine to cause a greater horizontal inhomogeneity, so that energy from the surface layer descends quickly, travelling equatorward and downward. Since waves at any point arrive from different latitudes, spectra no longer consist of discrete peaks but are more continuous and broader than those in the constant-f model. The waves are more intermittent because of the larger spectral width, and vertically less correlated in the thermocline because of a larger bandwidth of vertical modes. The vertical correlation in the deep ocean, however, is still high because the response is dominated by one or two low-order modes after 30 days of integration. As U decreases, the larger bandwidth of frequency increases the intermittency, and the larger bandwidth of vertical wavenumber decreases the vertical correlation. A superposition of travelling wind events intensifies the high-frequency end of the spectrum; a month-long travelling series of realistic strength can generate waves with amplitudes of order 4 cm/s in the deep ocean.It is suggested that propagating winds and linear dynamics are responsible for the generation of a large fraction of internal waves in the ocean at all depths. The main effect of nonlinearity and mean flow may be to shape the internal wave spectra to a ω-2 form.

scholarly journals Turbulence closure: turbulence, waves and the wave-turbulence transition – Part 1: Vanishing mean shear

2008 ◽  
Vol 5 (4) ◽  
pp. 545-580
Author(s):  
H. Z. Baumert ◽  
H. Peters
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Tidal Flow ◽  
Wave Turbulence ◽  
Mean Flow ◽  
Turbulent Length Scale ◽  
Turbulent Dissipation ◽  
New Model ◽  
Turbulence Transition ◽  
Ozmidov Scale

Abstract. A new two-equation, closure-like turbulence model for stably stratified flows is introduced which uses the turbulent kinetic energy (K) and the turbulent enstrophy (Ω) as primary variables. It accounts for mean shear – and internal wave-driven mixing in the two limits of mean shear and no waves and waves but no mean shear, respectively. The traditional TKE balance is augmented by an explicit energy transfer from internal waves to turbulence. A modification of the Ω-equation accounts for the effect of the waves on the turbulence time and space scales. The latter is based on the assumption of a non-zero constant flux Richardson number in the limit of vanishing mean-flow shear when turbulence is produced exclusively by internal waves. The new model reproduces the wave-turbulence transition analyzed by D'Asaro and Lien (2000). At small energy density E of the internal wave field, the turbulent dissipation rate (ε) scales like ε~E2. This is what is observed in the deep sea. With increasing E, after the wave-turbulence transition has been passed, the scaling changes to ε~E1. This is observed, for example, in the swift tidal flow near a sill in Knight Inlet. The new model further exhibits a turbulent length scale proportional to the Ozmidov scale, as observed in the ocean, and predicts the ratio between the turbulent Thorpe and Ozmidov length scales well within the range observed in the ocean.

Mean flow generation due to longitudinal librations of sidewalls of a rotating annulus

2020 ◽  
Vol 114 (6) ◽  
pp. 742-762
Author(s):  
Michael V. Kurgansky ◽  
Torsten Seelig ◽  
Marten Klein ◽  
Andreas Will ◽  
Uwe Harlander
Keyword(s):  
Mean Flow ◽  
Flow Generation

Mean flow generation in a two-layer system under circularly polarized vibrations

2011 ◽  
Vol 46 (4) ◽  
pp. 536-547
Author(s):  
D. V. Lyubimov ◽  
G. L. Khil’ko
Keyword(s):  
Mean Flow ◽  
Layer System ◽  
Circularly Polarized ◽  
Flow Generation

The deepening of a mixed layer in a stratified fluid

1975 ◽  
Vol 71 (2) ◽  
pp. 385-405 ◽  
Author(s):  
P. F. Linden
Keyword(s):  
Potential Energy ◽  
Internal Waves ◽  
Mixed Layer ◽  
Turbulent Energy ◽  
Stratified Fluid ◽  
Homogeneous Field ◽  
Constant Density ◽  
Simple Relationship ◽  
Mean Flow ◽  
Mixing Rate

In this paper two aspects of the deepening of a mixed layer in a stratified fluid are examined in the laboratory. The first is the deepening of a layer into a region of constant density gradient. Turbulence is produced by an oscillating grid which generates a horizontally homogeneous field of motion with no significant mean flow. It is found that the rate at which the potential energy of the basic stratification is increased by the mixing does not bear a simple relationship to the rate of energy input by the grid. On the other hand, when allowance is made for the decay of turbulent energy away from the grid and only that portion to reach the bottom of the mixed layer is considered, the rate of potential energy increase is found to be proportional to this available energy. The second aspect to be discussed is the effect of energy radiation by internal waves in the region below the mixed layer. Estimates are made of the possible loss of energy to these waves, which reduces the amount available to deepen the layer. An experimental demonstration of up to 50 % reduction in the mixing rate due to the presence of internal waves is given. Finally, the implications of these results are discussed in the light of current theoretical models of the deepening process.

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