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.

A new mechanism for generating a bolus within a double layer following Scott Russell

2021 ◽  
Author(s):  
Johan Fourdrinoy ◽  
Julien Dambrine ◽  
Madalina Petcu ◽  
Morgan Pierre ◽  
Germain Rousseaux
Keyword(s):  
Surface Deformation ◽  
Wave Train ◽  
Surrounding Medium ◽  
Negative Polarity ◽  
National Academy Of Sciences ◽  
Dispersive Waves ◽  
Dual Nature ◽  
Free Surface Deformation ◽  
Academy Of Sciences ◽  
Dead Water

<p>While seeking to revisit an old experiment of John Scott Russell, we discovered a new mechanism for generating a non-shoaling bolus (an ovoid coherent mass of recirculating mixed fluids immerged in a surrounding medium/a of different density/ies) propagating along a pycnocline. In a study about dead-water (Fourdrinoy et al. 2020), a wave resistance phenomenon induced by internal waves formation at the interface between waters of different densities, we modified the setup used by Scott Russell. The Scottish engineer studied the formation and propagation of dispersive waves when an object is removed from a laterally confined open channel with a shallow layer of water. The “vacuum” created by the mass removal generates a linear dispersive free surface deformation with a front of negative polarity followed by a wave train. If we extend this configuration to a two-layers stratification, we can observe a linear dispersive wave with negative polarity à la Scott Russell, propagating along the interface. In addition, the removal of the object generates under certain conditions a bolus which induces a mixing zone and a gradient transition layer. We will present this new method of boluses creation, as well as an experimental characterization with space-time diagrams thanks to a subpixel detection procedure.</p><p>The dual nature of the dead-water phenomenology: Nansen versus Ekman wave-making drags.<br>Johan Fourdrinoy, Julien Dambrine, Madalina Petcu, Morgan Pierre and Germain Rousseaux.<br>Proceedings of the National Academy of Sciences, Volume 117, Issue 29, p. 16739-16742, July 2020.</p>

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.

Internal Waves in Laboratory Experiments

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

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

scholarly journals Resurrecting dead-water phenomenon

2011 ◽  
Vol 18 (2) ◽  
pp. 193-208 ◽  
Author(s):  
M. J. Mercier ◽  
R. Vasseur ◽  
T. Dauxois
Keyword(s):  
Internal Waves ◽  
Large Amplitude ◽  
Experimental Studies ◽  
Nonlinear Effects ◽  
Stratified Fluid ◽  
Nonlinear Internal Waves ◽  
Induced Drag ◽  
Wave Induced ◽  
Dead Water ◽  
Peculiar Phenomenon

Abstract. We revisit experimental studies performed by Ekman on dead-water (Ekman, 1904) using modern techniques in order to present new insights on this peculiar phenomenon. We extend its description to more general situations such as a three-layer fluid or a linearly stratified fluid in presence of a pycnocline, showing the robustness of dead-water phenomenon. We observe large amplitude nonlinear internal waves which are coupled to the boat dynamics, and we emphasize that the modeling of the wave-induced drag requires more analysis, taking into account nonlinear effects. Dedicated to Fridtjöf Nansen born 150 yr ago (10 October 1861).

Mantle flow in planets: lessons from sugar syrup, hair gel, milk skin and marble cake.

2020 ◽  
Author(s):  
Anne Davaille
Keyword(s):  
Laboratory Experiments ◽  
New Physics ◽  
Dimensional Structure ◽  
Short Time Scale ◽  
Mantle Flow ◽  
Cold Surface ◽  
Mantle Dynamics ◽  
Dual Nature ◽  
The Earth ◽  
New Phenomena

<p>Even in the eon of supercomputers, I would claim that laboratory experiments remain an invaluable tool to investigate new phenomena and old problems, for at least 6 reasons:  (1) Since they let nature solve the equations, they can explore new phenomena for which such equations do not yet exist. (2) You usually can turn around them and have a good look at their three-dimensional structure. (3) You can observe their evolution through time. (4) you can simplify the system until you understand something ! (5) On the other hand, experiments can explore ranges of parameters, or geometries, where the equations are too challenging to be solved analytically or even numerically. (6) They are at the same time fun and thought-provoking. So yes, laboratory experiments are crucial for exploring new physics, testing theories and computer codes, and show your students, colleagues and family « how it works ». <br>Mantle dynamics, and thermal convection, is a good example.  The emergence of mantle convection models was dictated by the failure of static, conductive, and/or radiative thermal history models to account for the mantle temperature regime, the Earth’s energy budget, and the Earth’s lateral surface motions. Convection, which transports heat by material flow, is the only other physical mechanism capable of explaining these observations. The force driving flow is gravity, whereby material lighter than its environment rises, while denser material sinks. Such density anomalies can be produced by differences in composition and/or temperature. Then, the flow patterns produced by convection also strongly depend on the way the material deforms when submitted to a force: cold surface rocks break (typical of a solid) on short time scale and distances, while hot mantle rocks creep (typical of a liquid !) on geological time scales. This dual nature of a solid and a liquid is the main source of complexity, and debate, in mantle dynamics. Modern physics calls these solid-liquid materials « soft matter », and we use plenty of them in the everyday life and in the kitchen. I will show how differently mantle plumes and lithospheric plates form in honey syrup, hair gel, milk and cake. And how marble cake can help us understand mantle mixing.</p>

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>

STRONG CHAOS IN A FORCED NEGATIVE CONDUCTANCE SERIES LCR CIRCUIT

2005 ◽  
Vol 15 (02) ◽  
pp. 637-651 ◽  
Author(s):  
K. THAMILMARAN ◽  
D. V. SENTHILKUMAR ◽  
M. LAKSHMANAN ◽  
A. ISHAQ AHAMED
Keyword(s):  
Mathematical Model ◽  
Laboratory Experiments ◽  
Circuit Simulation ◽  
Period Doubling ◽  
Largest Lyapunov Exponent ◽  
Dual Nature ◽  
Statistical Studies ◽  
Torus Breakdown ◽  
Negative Conductance ◽  
The Rich

A negative conductance forced LCR circuit exhibiting strong chaos via the torus breakdown route as well as period-doubling route is described. The strong chaoticity is evidenced by the high value of the largest Lyapunov exponent and statistical studies. The dual nature of this circuit exhibiting the rich dynamics of both the Murali–Lakshmanan–Chua (MLC) circuit [Murali et al., 1994] and the circuit due to Inaba and Mori [1991] is also explored. The performance of the circuit is investigated by means of laboratory experiments, PSpice circuit simulation, numerical integration of appropriate mathematical model and explicit analytical studies, which all agree well with each other.

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