Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session E1: Geophysical: Oceanographic III |
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Chair: Eric Paterson, Virginia Polytechnic Institute and State University Room: 323 |
Sunday, November 24, 2013 4:45PM - 4:58PM |
E1.00001: On the study of radar backscattering of ocean surface in response to rainfall Xinan Liu, Quanan Zheng, Ren Liu, James H. Duncan A model of radar backscattering from the ocean surface in response to rainfall is developed. The model shows that the radar return intensity is a function of the wavelength and incident angle of the radar waves and the rain rate. The model explains the differences between the radar response to rain rate simultaneously observed by C-band ASAR and ground-based weather radar. An experiment on the simultaneous measurements of the characteristics of the ocean surface in response to rainfall and its radar back-scatter is performed in the laboratory. The experiment is carried out in a water pool that is 1.22~m by 1.22~m with a water depth of 0.3~m. Artificial rainfall is generated from an array of hypodermic needles. The surface characteristics including crowns, stalks and ring waves are measured with a cinematic Laser-Induced-Florescence (LIF) technique while secondary droplets are measured with a shadowgraph technique. The radar backscattering signal is recorded with a dual-polarized, ultra-wide band radar. The frequency dependence and polarization of the radar signatures due to the surface features are discussed. [Preview Abstract] |
Sunday, November 24, 2013 4:58PM - 5:11PM |
E1.00002: Turbulent bubbly flow under unsteady breaking waves Morteza Derakhti, James Kirby Wave breaking is a highly dissipative process, and also a source of turbulence in the ocean surface layer. It entrains a large volume of air in bubbles that rapidly evolves into a distribution of bubble sizes which interacts with fluid turbulence and organized motions, leads to a continuum time-dependent void fraction of bubbles. In this presentation, we use a 3D VOF-based Navier-Stokes solver extended to incorporate entrained bubble populations using an Eulerian-Eulerian formulation for a poly-disperse bubble phase, to consider an isolated, deep-water breaking event. We examine anisotropic non-stationary turbulence structure, momentum exchange between dispersed bubbles and liquid phase, bubble effects on mean and turbulent field, shear- and bubble-induced dissipation, bubble void fraction distribution and integral properties of the bubble plume both in spilling and plunging breakers. Comparison of mean and turbulent velocities, void fraction distributions and integral properties of the bubble plume show that the model is capable of capturing the large scale of turbulence and bubble plume kinematics and dynamics fairly well, and the inclusion of bubbles gives better results in terms of total dissipation and turbulent velocities. [Preview Abstract] |
Sunday, November 24, 2013 5:11PM - 5:24PM |
E1.00003: Magnetic Field Induced by a Submerged Inhomogenous Current Daniel Sobien, Eric Paterson A one-way coupled approach has been developed for studying the electromagnetic field induced by a submerged inhomogenous current. The method is based upon solving the Navier-Stokes equations, transport equations for salinity and temperature, the UNESCO equation of state for seawater density and conductivity, and a steady-state Poisson equation for the magnetic-field perturbation. The computational domain includes both the ocean and the atmosphere. Simulations are conducted for a net-zero-momentum wake in a linearly stratified ocean, and the influence of depth and Brunt-V\"ais\"al\"a frequency is studied. Simulation data will quantify the magnitude and distribution of magnetic-field perturbation. [Preview Abstract] |
Sunday, November 24, 2013 5:24PM - 5:37PM |
E1.00004: Large-eddy simulation of oil slicks from deep water blowouts Di Yang, Marcelo Chamecki, Charles Meneveau Deep water blowouts generate plumes of oil droplets and gas bubbles that rise through, and interact with various layers of the ocean. When plumes reach the ocean mixed layer (OML), the interactions among plume, Ekman Spiral and Langmuir turbulence strongly affect the final rates of dilution and bio-degradation. The present study aims at developing a large-eddy simulation (LES) capability for the study of the physical distribution and dispersion of petroleum (oil and gas) under the action of physical oceanographic processes in the OML. In the current LES, the velocity and temperature fields are simulated using a hybrid pseudo-spectral and finite-difference scheme; the oil/gas field is described by an Eulerian concentration field and it is simulated using a bounded finite-volume scheme. A variety of subgrid-scale models for the flow solver are implemented and tested. The LES capability is then applied to the simulation of oil plume dispersion in the OML, which is initially released from a point source below the thermocline. Graphical visualization of the LES results shows surface oil slick distribution consistent with the satellite and aerial images of surface oil slicks reported in the literature. [Preview Abstract] |
Sunday, November 24, 2013 5:37PM - 5:50PM |
E1.00005: Comparing fixed and dynamic-salinity models of sea ice David Rees Jones, Grae Worster The bulk salinity of sea ice has long been poorly represented in climate models. We have incorporated a physically-derived parameterization of ice desalination by gravity drainage in terms of a convective upwelling velocity into a one-dimensional thermodynamic sea-ice model of the kind currently used in coupled climate models. Our parameterization allows us to determine salt fluxes from sea ice corresponding to the evolution of the bulk salinity of the ice, in contrast to current, established models that prescribe the ice salinity. This improves the predictive power and responsiveness of climate models in terms of buoyancy fluxes to the polar oceans, and also the thermal and mechanical properties of sea ice, which depend on its salinity. We discuss and compare our parameterization to other recent parameterizations of gravity drainage, as well as existing fixed-salinity models, both in terms of laboratory experiments and deep ocean mixed layer calculations in the case of growing first-year ice. These comparisons explain why the direct effect of ice salinity on growth is relatively small (though not negligible), and highlight substantial differences in salt fluxes into the polar oceans. [Preview Abstract] |
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