Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session QH: GFD: General III |
Hide Abstracts |
Chair: Joseph Barranco, San Francisco State University Room: Long Beach Convention Center 103C |
Tuesday, November 23, 2010 12:50PM - 1:03PM |
QH.00001: Elastic response of ice sheet-shelf system Roiy Sayag, Grae Worster An ice sheet that spreads into an ocean is forced to bend due to its buoyancy, and delaminate from the ground to form an ice shelf. The location of the transition between the grounded sheet and the ungrounded shelf is defined as the grounding-line. The dynamics of grounding lines may have a critical effect on the stability of ice sheets, and determining the position of those free boundaries requires additional conditions that can be hard to constrain. We model such a sheet-shelf system as an elastic sheet, partially resting on an elastic substrate and partially resting on an ocean. Solving the two parts simultaneously by matching moments across the grounding line, we can avoid imposing an explicit boundary condition at the grounding line. In the limit of very stiff ground, a Stefan-like boundary condition can be identified at the grounding line, which simplifies the problem into solving only for the shelf. We present a good agreement between our theoretical predictions and laboratory experiments made using thick elastic sheets and a dense salt solution. We evaluate the variation of grounding line position with bed stiffness numerically, and estimate the relevance of an elastic response to viscous ice sheets. [Preview Abstract] |
Tuesday, November 23, 2010 1:03PM - 1:16PM |
QH.00002: Fracturing of rocks by ice Ioanna Vlahou, Grae Worster Fracturing of water-saturated rocks occurs frequently in cold climates and is caused by water freezing inside their pores. It is an important problem for both engineers and scientists as it can affect pavements and the foundations of buildings, and is a major erosional force in rocks. We consider the problem of the propagation of an ice-filled three-dimensional penny-shaped cavity in a water-saturated elastic porous medium. Between the ice and the rock, disjoining thermomolecular forces create a pre-melted film of water and cause flow of pore water from the surrounding rock into the cavity. The Darcy flow of water through the medium is limited by the permeability of the rock. Linear elasticity is used to describe the pressure distribution on the rock and to determine the propagation rate of the tip of the cavity. The Gibbs-Thompson relation dictates a maximum curvature for the ice tip, hence the extent of the ice depends on the aspect ratio of the cavity and the temperature of the ice front. We obtain a set of linear integro-differential equations coupled with two non-linear conditions on the crack tip propagation and the ice extent. We investigate the existence of solutions describing the evolution of the cavity, identifying the important physical parameters and applying the results to examples of rocks and clays. [Preview Abstract] |
Tuesday, November 23, 2010 1:16PM - 1:29PM |
QH.00003: Nonlinear spin-up of a thermally stratified fluid in cylindrical geometries J. Rafael Pacheco, Roberto Verzicco, Sergey Smirnov We present a numerical study of incremental spin-up of a thermally-stratified fluid enclosed within right circular cylinder/annulus with rigid bottom and side walls and stress-free upper surface.This investigation reveals a feasibility for transition from an axisymmetric initial circulation to non-axisymmetric flow patterns, and it is motivated by the desire to compare the spin-up for Dirichlet and Neumann thermal boundary conditions. The numerical simulations demonstrate that the destabilizing mechanism is not purely baroclinic, but that vertical and horizontal shears may contribute to the instability. By characterizing the azimuthal instabilities without introducing any simplification we were able to assess to what extent an insulating boundary condition changes the time-dependent emergence of the instability. Our results agree with previous experimental data and provide a framework for understanding the role played by the baroclinic vorticity in the development of instabilities in thermally-stratified incremental spin-up flows. [Preview Abstract] |
Tuesday, November 23, 2010 1:29PM - 1:42PM |
QH.00004: Experimental study of atmospheric wind and ocean surface wave interaction Arindam Singha, Reza Sadr The exchange of momentum between the wind and the ocean surface is the primary source of various oceanic phenomenons, both in large and small-scales. Upon reviewing the existing literature, there seems to be a missing link between the standard atmospheric and oceanic-circulation models. This is due to the difficulty of the theoretical formulation for a proper model, given that the ocean-air interface varies in space and time simultaneously; and the difficulty of obtaining reliable experimental data on ocean surface and atmospheric turbulence characteristics. An experimental site is being developed at the under-construction New Doha International Airport (NDIA) in Qatar to obtain simultaneous atmospheric and ocean surface data. The site is located at the end of an aircraft approach light line which is about 500 m into the sea. Water at this location is about 6-m deep and ocean floor is almost flat terrain in all directions. The necessary measurement will be accomplished by synchronized operation of three sonic anemometers and two CCD cameras. An overview of the experimental site, along with preliminary data showing the weather trend and the feasibility of the study is reported. [Preview Abstract] |
Tuesday, November 23, 2010 1:42PM - 1:55PM |
QH.00005: Fluxes across double-diffusive interfaces: a one-dimensional-turbulence study Esteban Gonzalez-Juez, Alan Kerstein, David Lignell The parametrization of the fluxes of heat and salt across double-diffusive interfaces is of interest in geophysics, astrophysics, and engineering. The present work is a parametric study of these fluxes using one-dimensional-turbulence (ODT) simulations. Its main distinction is that it considers a parameter space larger than previous studies. Specifically, this work considers the effect on the fluxes of the stability parameter $R_{\rho}$, Rayleigh number $Ra$, Prandtl number, Lewis number, and Richardson number. The ratio $Ra/R_{\rho}$ is found to be a dominant parameter. Here $Ra/R_{\rho}$ can be seen as a ratio of destabilizing and stabilizing effects. Trends predicted by the simulations are in good agreement with previous models and available measurements. [Preview Abstract] |
Tuesday, November 23, 2010 1:55PM - 2:08PM |
QH.00006: Settling-induced heat transport Francois Blanchette, William Douandju, Sydney Montroy We discuss the influence of settling particles on heat transport within suspensions. We focus on particles that equilibrate their temperature with the surrounding fluid much faster than their typical settling time. Such particles act as heat carriers and heat transport therefore occurs through both diffusion and particle settling. We quantify this effect by deriving the relevant governing equations. We investigate the stabilizing effect of this enhanced transport on unstable density gradients via a linear stability analysis. We conclude by discussing systems where this effect is important, such as rivers coming into the ocean, magma chambers, and when large concentrations of volcanic and forest fire ashes are present in the atmosphere. [Preview Abstract] |
Tuesday, November 23, 2010 2:08PM - 2:21PM |
QH.00007: PSI of the oceanic internal tide Jeroen Hazewinkel, Yue-Kin Tsang, Kraig B. Winters, William R. Young The dynamics of a forced, low-mode oceanic internal tide propagating poleward on a beta plane are investigated numerically. We focus on the instability that transfers energy from the forced wave to waves at subharmonic frequency near the critical latitude where the subharmonic and local inertial frequencies match. Through parametric subharmonic instability (PSI), energy is transferred to motions that have a fine-scale modal structure, both in the horizontal and vertical directions. During the exponential growth phase, these motions do not provide a major sink of energy for the tide. A significant reduction in poleward energy flux is only observed once the amplitude of the near-inertial waves becomes comparable to tide itself and dynamics become fully non-linear. The observed decrease flux is approximately 15 percent, much less than was found in previous numerical studies but in reasonable agreement with recent estimates from observational data taken near the critical latitude in the Pacific. [Preview Abstract] |
Tuesday, November 23, 2010 2:21PM - 2:34PM |
QH.00008: Nonlinear effects associated with harmonic forcing of the flow in a rotating sphere Alban Sauret, David C\'ebron, Cyprien Morize, Michael Le Bars, St\'{e}phane Le Diz\`{e}s Significant axisymmetric stationary flows can be generated by the action of an harmonic forcing on a rotating fluid in a sphere. Such a mechanism could be of fundamental importance in natural systems, for instance in planetary cores subject to libration, precession or tides. Using a weakly non-linear analysis, we first show that the mechanism of zonal flow generation is fully generic: the main contribution in the bulk always comes from the non-linear self-interaction of the viscous boundary layer flow induced by a multipolar forcing. The analytical study predicts that the zonal flow amplitude scales as the square value of the considered forcing and is independent of the Ekman number. These results are confirmed by systematic PIV measurements in a rotating sphere and by asixymmetric simulations for the case of libration. [Preview Abstract] |
Tuesday, November 23, 2010 2:34PM - 2:47PM |
QH.00009: The role of non-QG dynamics in the formation and equilibration of eddies in the ocean and atmosphere J.R. Taylor, K.S. Smith, R. Ferrari The goal of this research is to examine the effect of unbalanced dynamics on the generation and evolution of eddies in the ocean and atmosphere. Numerical simulations of an eddy field generated through baroclinic instability of a jet in geostrophic balance on an f-lpane will be presented. Two numerical codes are used; one solves the Boussinesq nonhydrostatic Navier-Stokes equations, and the other solves the quasi-geostrophic (QG) equations. Consistent with previous literature, loss of balance arises spontaneously from the balanced initial condition in the Boussinesq model, but not in the QG model which filters out any inertia-gravity and high Rossby number motions. The novelty of our approach is that we can investigate the role of unbalanced motions on the evolution of the eddy field by comparing simulations run with the two models. Pairs of simulations of jets starting at progressively larger Rossby numbers show that non-QG dynamics become more important as the Rossby number is increased. Particular emphasis will be placed on the forward cascade of tracer variance, enstrophy, and energy from large to small scales. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700