Experiments with density currents on a sloping bottom in a rotating fluid

Etling, Dieter; Gelhardt, F; Schrader, U; Brennecke, F; Kühn, Gregor; D'Hieres, G. Chabert; Didelle, Henri

doi:10.1016/s0377-0265(99)00031-7

Cited by 51 publications

(62 citation statements)

References 33 publications

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“…While the influence of Coriolis forces upon turbidity currents is acknowledged in several reviews (Middleton 1993;Huppert 1998;Kneller & Buckee 2000) and in theoretical studies (Nof 1996;Emms 1999;Ungarish & Huppert 1999), the present paper is the first experimental investigation to study turbidity currents on a rotating platform. The results in the present paper build upon what has been learned in the oceanographic context, where there have been many previous studies on the influence of Coriolis forces on non-sedimenting density currents (Griffiths 1986; Shapiro & Zatsepia 1997;Jacobs & Ivey 1998;Etling et al 2000;Hallworth et al 2001;Cenedese et al 2004;Davies et al 2006).…”

Section: Introductionsupporting

confidence: 76%

“…Due to the radial symmetry of the cone, the area over which the dense current can entrain is the same in all experiments. This is an advantage over the related experiments of Etling et al (2000) or Cenedese et al (2004) where the dense current flowed down a flat slope and hence the surface area over which entrainment into the dense currents can occur increased dramatically for strongly rotationally deflected currents. To determine the entrainment ratio from the measured depth of dense pool in the experiments, we use the relationship between the amount of mixing and entrainment ratio, introduced by Cenedese et al (2004).…”

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confidence: 92%

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Particle-Laden Flow

Geurts¹,

Clercx²,

Uijttewaal³

2007

ERCOFTAC Series

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PrefaceThe dispersion of particles in a flow is of central importance in various geophysical and environmental problems. The spreading of aerosols and soot in the air, the growth and dispersion of plankton blooms in seas and oceans, or the transport of sediment in rivers, estuaries and coastal regions are striking examples.These problems are characterized by strong nonlinear coupling between several dynamical mechanisms such as convective sweeping, rotation, buoyancy, bio-physical influences and interactions between particles and fluid. As a result, processes on widely different length and time scales are simultaneously of importance. These range from Kolmogorov scales at which the flow at particle-scales is central, to much larger-scale structures that can be appreciated best via satellite observations. The multiscale nature of this challenging field motivated this colloquium that was organized by the recently established Dutch Platform for Geophysical and Environmental Fluid-mechanics (PGEF). The meeting took place at the University of Twente (the Netherlands), June 21-23, 2006. In total 55 participants from 13 different countries and 4 different continents contributed to the colloquium. The six keynote speakers provided reviews and recent research findings of areas that were central to the theme of the colloquium. These keynote lectures constituted the framework for the rest of the program, which contained 33 contributed papers, several of which are collected in this book.Issues related to the large-scale environmental aspects of particle-laden flows were addressed by considering turbulence modulation arising in high density clay-laden flows, and by focussing on transport processes in the stratosphere and its relevance to climate and weather predictions. Fundamental aspects of transport of particles formed the topic of the second day of the colloquium. Insights from experimental and computational research were combined to understand the distortion of flow in the neighborhood of embedded particles. Aspects of Lagrangian statistics in turbulence were discussed at length, addressing the dispersion of embedded point particles. Bridging the environ-VI Preface mental and the fundamental aspects of particle-laden flows was the topic of the final day of the colloquium. The Lagrangian dispersion of particles in the context of their environmental setting was presented. The closing lecture provided a synopsis of transport processes in particle-laden flow in which possibilities of multi-resolution, multi-physics modeling and monitoring were discussed.The colloquium on particle-laden flow was organized under the auspices of EUROMECH, the European Mechanics Society, and the Universities of Technology of Delft, Eindhoven and Twente. It was supported financially by a number of institutions: ERCOFTAC (European Research Council On Flow, Turbulence and Combustion), COST Action P20 'LES-AID' (COoperation in the field of Science and Technology), the Netherlands foundation for fundamental research of matter (FOM), the Netherland...

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Section: Introductionsupporting

confidence: 76%

mentioning

confidence: 92%

Particle-Laden Flow

Geurts¹,

Clercx²,

Uijttewaal³

2007

ERCOFTAC Series

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“…In no experiments did we observe wavy instabilities in the Ekman layer itself, as has been observed by Lane-Serff & Baines (1998); Etling et al (2000), and Cenedese et al (2004). This is because our experiments are run in the regime with small Froude number, based on the ratio of the observed spreading rate to the theoretical shallow water speed of the Ekman layer:…”

Section: Ekman Layermentioning

confidence: 61%

Rotating dense currents on a slope. Part 1. Stability

et al. 2004

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Using a novel experimental set-up, we examine the stability of an axisymmetric dense current of fluid on a sloping bottom in a rotating frame of reference. In a cylindrical tank on a rotating table, saline fluid is injected through an annular mesh encircling a cone of 1/15 slope. The resulting ring of fluid becomes unstable to periodic sinusoidal waves, whose characteristics are examined as a function of the ambient fluid depth, the rotation rate, and the salinity and depth of the dense current, the latter being related to the injection time. For experiments with relatively low-salinity currents, we find the phase speed of the instability is proportional to the rotation rate, Ω, rather than being proportional to the Nof speed, which varies as 1/Ω. Likewise, the number of waves observed is found to be inconsistent with existing theories for baroclinic instability of a dense current on a sloping bottom with a stationary ambient.Surface tracers reveal that significant currents are induced in the ambient by the injection of the saline fluid and we propose that it is the coupling between the surface and bottom flow that ultimately controls the observed dynamics. In particular, we propose that barotropic instability of the surface flow controls the behaviour of the low-salinity current and, using potential vorticity conservation, we predict the phase speed of the instability should indeed be proportional to Ω. The experimental results are also compared with related work in which eddies and Ekman layers evolve from dense fluid injected from a localized source.

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“…Shapiro and Zatsepin, 1997;Etling et al, 2000;Cenedese et al, 2004;Sutherland et al, 2004). In addition to a simple laminar flow regime, several more complex regimes have been observed: roll-waves (Shapiro and Zatsepin, 1997) as well as vortices and eddies (Lane-Serff and Baines, , 2000Etling et al, 2000). This paper revisits the laboratory experiments by Shapiro and Zatsepin (1997) by applying a 3-D ocean model to the study of cascading on a steeply-sloping rotating cone.…”

Section: Introduction a Dense Water Cascadingmentioning

confidence: 94%

Numerical simulations of dense water cascading on a steep slope

Wobus¹,

Shapiro²,

Maqueda³

et al. 2011

j mar res

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The sinking of dense shelf waters down the continental slope (or "cascading") contributes to oceanic water mass formation and carbon cycling. Cascading over steep bottom topography is studied here in numerical experiments using POLCOMS, a 3-D ocean circulation model using a terrain-following s-coordinate system. The model setup is based on a laboratory experiment of a continuous dense water flow from a central source on a conical slope in a rotating tank. The governing parameters of the experiments are the density difference between plume and ambient water, the flow rate, the speed of rotation and (in the model) diffusivity and viscosity. The descent of the dense flow as characterized by the length of the plume as a function of time is studied for a range of parameters. Very good agreement between the model and the laboratory results is shown in dimensional and nondimensional variables. It is confirmed that a hydrostatic model is capable of reproducing the essential physics of cascading on a very steep slope if the model correctly resolves velocity veering in the bottom boundary layer. Experiments changing the height of the bottom Ekman layer (by changing viscosity) and modifying the plume from a 2-layer system to a stratified regime (by enhancing diapycnal diffusion) confirm previous theories, demonstrate their limitations and offer new insights into the dynamics of cascading outside of the controlled laboratory conditions.

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Experiments with density currents on a sloping bottom in a rotating fluid

Cited by 51 publications

References 33 publications

Particle-Laden Flow

Particle-Laden Flow

Rotating dense currents on a slope. Part 1. Stability

Numerical simulations of dense water cascading on a steep slope

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