Internal Waves in Laboratory Experiments

2014 ◽  
pp. 193-212
Author(s):  
Bruce Sutherland ◽  
Thierry Dauxois ◽  
Thomas Peacock
Keyword(s):  
Internal Waves ◽  
Laboratory Experiments

Sediment Resuspension and Transport by Internal Solitary Waves

2019 ◽  
Vol 51 (1) ◽  
pp. 129-154 ◽  
Author(s):  
Leon Boegman ◽  
Marek Stastna
Keyword(s):  
Internal Waves ◽  
Laboratory Experiments ◽  
Sediment Resuspension ◽  
Vital Role ◽  
Continental Margins ◽  
Scale Models ◽  
Key Driver ◽  
Induced Currents ◽  
Wave Induced ◽  
Oriented Research

Large-amplitude internal waves induce currents and turbulence in the bottom boundary layer (BBL) and are thus a key driver of sediment movement on the continental margins. Observations of internal wave–induced sediment resuspension and transport cover significant portions of the world's oceans. Research on BBL instabilities, induced by internal waves, has identified several mechanisms by which the BBL is energized and sediment may be resuspended. Due to the complexity of the induced currents, process-oriented research using theory, direct numerical simulations, and laboratory experiments has played a vital role. However, experiments and simulations have inherent limitations as analogs for oceanic conditions due to disparities in Reynolds number and grid resolution, respectively. Parameterizations are needed for modeling resuspension from observed data and in larger-scale models, with the efficacy of parameterizations based on the quadratic stress largely determining the accuracy of present field-scale efforts.

scholarly journals The dual nature of the dead-water phenomenology: Nansen versus Ekman wave-making drags

2020 ◽  
Vol 117 (29) ◽  
pp. 16770-16775
Author(s):  
Johan Fourdrinoy ◽  
Julien Dambrine ◽  
Madalina Petcu ◽  
Morgan Pierre ◽  
Germain Rousseaux
Keyword(s):  
Internal Waves ◽  
Laboratory Experiments ◽  
Analytical Description ◽  
Unsteady Motion ◽  
Linear Regime ◽  
Dual Nature ◽  
Asymptotic Speed ◽  
Propulsion Force ◽  
Initial Acceleration ◽  
Dead Water

A ship encounters a higher drag in a stratified fluid compared to a homogeneous one. Grouped under the same “dead-water” vocabulary, two wave-making resistance phenomena have been historically reported. The first, the Nansen wave-making drag, generates a stationary internal wake which produces a kinematic drag with a noticeable hysteresis. The second, the Ekman wave-making drag, is characterized by velocity oscillations caused by a dynamical resistance whose origin is still unclear. The latter has been justified previously by a periodic emission of nonlinear internal waves. Here we show that these speed variations are due to the generation of an internal dispersive undulating depression produced during the initial acceleration of the ship within a linear regime. The dispersive undulating depression front and its subsequent whelps act as a bumpy treadmill on which the ship would move back and forth. We provide an analytical description of the coupled dynamics of the ship and the wave, which demonstrates the unsteady motion of the ship. Thanks to dynamic calculations substantiated by laboratory experiments, we prove that this oscillating regime is only temporary: the ship will escape the transient Ekman regime while maintaining its propulsion force, reaching the asymptotic Nansen limit. In addition, we show that the lateral confinement, often imposed by experimental setups or in harbors and locks, exacerbates oscillations and modifies the asymptotic speed.

Estimating pressure and internal-wave flux from laboratory experiments in focusing internal waves

2020 ◽  
Vol 61 (11) ◽  
Author(s):  
Pierre-Yves Passaggia ◽  
Vamsi K. Chalamalla ◽  
Matthew W. Hurley ◽  
Alberto Scotti ◽  
Edward Santilli
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Laboratory Experiments ◽  
Wave Flux

Idealized Numerical Modelling of Internal Waves Through Density Staircases

2021 ◽  
Author(s):  
Mikhail Schee ◽  
Nicolas Grisouard
Keyword(s):  
Internal Waves ◽  
Laboratory Experiments ◽  
Equations Of Motion ◽  
Vertical Mixing ◽  
Boussinesq Equations ◽  
The Arctic ◽  
Inertial Wave ◽  
Ice Floes ◽  
Mixed Layers ◽  
Transmission And Reflection

<p>The Arctic Ocean contains a warm layer originating from the Atlantic Ocean below the pycnocline which has a thermohaline staircase structure that inhibits vertical mixing. If this heat were to rise to the surface, the rate of sea ice loss would increase dramatically. Wind stress and ice floes generate internal waves which can cause vertical mixing. As the ice cover in the Arctic continues to decline, it will be important to predict how these changing internal waves propagate through such stratification profiles. Here, we investigate how density staircases enhance or limit downward near-inertial wave propagation. We use direct numerical simulations to solve the Boussinesq equations of motion using spectral methods. We simulate the propagation of internal waves through a vertically stratified fluid which includes one or more steps (i.e., mixed layers). We find that we reproduce the results of laboratory experiments showing transmission and reflection of internal waves from one or two mixed layers. We then extend our parameter regime to simulate the propagation of internal waves through a more realistic stratification profile tending toward that of the Arctic pycnocline.</p>

scholarly journals The wave instability pathway to turbulence

2013 ◽  
Vol 724 ◽  
pp. 1-4 ◽  
Author(s):  
Bruce R. Sutherland
Keyword(s):  
Internal Waves ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Wave Beam ◽  
Small Scale ◽  
Monochromatic Wave ◽  
Wave Instability ◽  
Analysis Techniques ◽  
Parametric Subharmonic Instability ◽  
The Waves

AbstractOne way that large-scale oceanic internal waves transfer their energy to small-scale mixing is through parametric subharmonic instability (PSI). But there is a disconnect between theory, which assumes the waves are periodic in space and time, and reality, in which waves are transient and localized. The innovative laboratory experiments and analysis techniques of Bourget et al. (J. Fluid Mech., vol. 723, 2013, pp. 1–20) show that theory can be applied to interpret the generation of subharmonic disturbances from a quasi-monochromatic wave beam. Their methodology and results open up new avenues of investigation into PSI through experiments, simulations and observations.

Laboratory experiments on intrusive flows and internal waves in a pycnocline

2001 ◽  
Vol 432 ◽  
pp. 285-311 ◽  
Author(s):  
V. S. MADERICH ◽  
G. J. F. VAN HEIJST ◽  
A. BRANDT
Keyword(s):  
Internal Waves ◽  
Wave Breaking ◽  
Laboratory Experiments ◽  
Cell Structure ◽  
Subsequent Evolution ◽  
Flow Measurements ◽  
Continuous Mixing ◽  
Flow Simulations ◽  
Horizontal Grid ◽  
Mixed Fluid

A laboratory study has been performed to simulate intrusive flows generated by internal wave-breaking activity in the oceanic pycnocline. Two different cases were considered. In the first set of experiments a short-duration source of motion was modelled by creating a finite region of well-mixed fluid. The collapse of this region resulted in intrusive flows and internal waves in the pycnocline. Attention was focused on the formation and subsequent evolution of solitary ‘bulges’ in the intrusion. Detailed flow measurements have revealed that the weak motion inside these bulges (which contain well-mixed fluid from the source) is organized in a four-vortex structure. Numerical flow simulations provided important information about the dynamics of this four-cell structure: the outer cells are associated with baroclinic generation of vorticity, while the inner cells are characterized by a balance between the advective and the viscous terms in the vorticity equation.In the second set of experiments continuous mixing was induced by a vertically oscillating, horizontal grid centred in the pycnocline. The mixed region collapses, thus forming an intrusive flow into the pycnocline and internal waves that propagate along the pycnocline at higher speed than the intrusion. It was found that the velocity of the intrusive flow is approximately constant and that its dynamics is controlled by an inertial–buoyancy balance. The parameters of the internal waves in both cases were compared with theory.

scholarly journals Computation of Density Perturbation and Energy Flux of Internal Waves from Experimental Data

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 119
Author(s):  
Lucie Bordois ◽  
Jonas Nycander ◽  
Alexandre Paci
Keyword(s):  
Experimental Data ◽  
Internal Waves ◽  
Energy Flux ◽  
Laboratory Experiments ◽  
Density Perturbation ◽  
Three Dimensions ◽  
Buoyancy Frequency ◽  
Periodic Field ◽  
Anomaly Field ◽  
Density Anomaly

We hereby present two different spectral methods for calculating the density anomaly and the vertical energy flux from synthetic Schlieren data, for a periodic field of linear internal waves (IW) in a density-stratified fluid with a uniform buoyancy frequency. The two approaches operate under different assumptions. The first method (hereafter Mxzt) relies on the assumption of a perfectly periodic IW field in the three dimensions (x, z, t), whereas the second method (hereafter MxtUp) assumes that the IW field is periodic in x and t and composed solely of wave components with downward phase velocity. The two methods have been applied to synthetic Schlieren data collected in the CNRM large stratified water flume. Both methods succeed in reconstructing the density anomaly field. We identify and quantify the source of errors of both methods. A new method mixing the two approaches and combining their respective advantages is then proposed for the upward energy flux. The work presented in this article opens new perspectives for density and energy flux estimates from laboratory experiments data.

Laboratory experiments on the resonance of internal waves on a finite height subcritical topography

2015 ◽  
Vol 65 (9-10) ◽  
pp. 1269-1274 ◽  
Author(s):  
Jinhu Wang ◽  
Xu Chen ◽  
Wei Wang ◽  
Qiang Li
Keyword(s):  
Internal Waves ◽  
Laboratory Experiments ◽  
Finite Height

Intrusive gravity currents from finite-length locks in a uniformly stratified fluid

2009 ◽  
Vol 635 ◽  
pp. 245-273 ◽  
Author(s):  
J. R. MUNROE ◽  
C. VOEGELI ◽  
B. R. SUTHERLAND ◽  
V. BIRMAN ◽  
E. H. MEIBURG
Keyword(s):  
Numerical Simulations ◽  
Internal Waves ◽  
Laboratory Experiments ◽  
Wave Speed ◽  
Gravity Currents ◽  
Fluid Density ◽  
Ambient Fluid ◽  
Experimental Conditions ◽  
Mode 2 ◽  
The Waves

Gravity currents intruding into a uniformly stratified ambient are examined in a series of finite-volume full-depth lock-release laboratory experiments and in numerical simulations. Previous studies have focused on gravity currents which are denser than fluid at the bottom of the ambient or on symmetric cases in which the intrusion is the average of the ambient density. Here, we vary the density of the intrusion between these two extremes. After an initial adjustment, the intrusions and the internal waves they generate travel at a constant speed. For small departures from symmetry, the intrusion speed depends weakly upon density relative to the ambient fluid density. However, the internal wave speed approximately doubles as the waves change from having a mode-2 structure when generated by symmetric intrusions to having a mode-1 structure when generated by intrusions propagating near the bottom. In the latter circumstance, the interactions between the intrusion and internal waves reflected from the lock-end of the tank are sufficiently strong and so the intrusion stops propagating before reaching the end of the tank. These observations are corroborated by the analysis of two-dimensional numerical simulations of the experimental conditions. These reveal a significant transfer of available potential energy to the ambient in asymmetric circumstances.

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