Bulletin of the American Physical Society
2006 59th Annual Meeting of the APS Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida
Session AG: U.S.-Mexico Minisymposium I: Geophysical Fluid Dynamics |
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Chair: Roberto Zenit, UNAM Mexico Room: Tampa Marriott Waterside Hotel and Marina Florida Salon 5 |
Sunday, November 19, 2006 8:00AM - 8:26AM |
AG.00001: Fluid exchange flows Herbert Huppert Flow flows from one container to another play important roles in many natural and industrial situations. The talk will describe the latest work on some of these. 1. The exchange flow of relatively dense, viscous fluid in a container connected by a vertical pipe to a container beneath it, initially full of relatively light fluid, will be discussed. This mimics the important exchange flow between a volcanic crater and a deep magma reservoir. A quantitative analysis of the flow will be presented. For the volcanic situation this allows the conduit radius to be evaluated from observations of the sulphur dioxide flux from the crater to the atmosphere. 2. A closed container initially full of liquid, which can drain into the atmosphere through a very long tube, displays different phenomena, which are associated with the compressibility of the air that exchanges space with the liquid. Three distinct regimes are observed, which we term: `popping'; `glugging'; and `slugging'. During each of these the container drains at a quite different rate. 3. Hot air in a house can be exchanged through doors and windows with the cooler air outside. The form and rate of exchange and its dependence on window geometry is of considerable architectural interest at the moment, if only to make our working environment as green as possible. New experiments and the associated concepts for this problem will be discussed. [Preview Abstract] |
Sunday, November 19, 2006 8:26AM - 8:52AM |
AG.00002: Experiments on coastal dispersion in a two-dimensional turbulent flow Luis Zavala Sanson Lagrangian dispersion in a turbulent, two-dimensional flow is analyzed by means of laboratory experiments. The results are oriented to understand the dispersion properties depending on the characteristics of the turbulence. The initial turbulent field is produced by forcing a number of vortices electromagnetically in a thin, conductive fluid layer in a square container. Below the tank, an array of 10 X 10 magnets is placed with their main magnetic field component directed up and downwards, alternatively. The fluid is set in motion by Lorentz forces when introducing an electrical current in the horizontal plane. This method allows one to reproduce approximately a complex turbulent initial flow. In particular, a continuous flow from a point source at one of the lateral walls is examined. This configuration resembles the discharge of a river into a lake or sea, or the generation of pollutants at coastal areas. A basic and rather intuitive result is that the discharged fluid spreads away from the wall more rapidly due to the turbulent interior flow than in the case without turbulence. It is shown that this behaviour depends on the Reynolds number and on the initial energetics of the turbulent field. The coastal discharge is transported when captured by strain-dominated areas between vortices, forming long filaments that spread into the flow domain. A number of techniques are proposed to quantify this transport. [Preview Abstract] |
Sunday, November 19, 2006 8:52AM - 9:18AM |
AG.00003: Booming Sand Dunes Melany Hunt, N.M. Vriend, K.S. Brantley, C.E. Brennen, R.W. Clayton In the southwestern United States and other locations around the world, large sand dunes can generate a loud booming sound during a natural or induced slumping event. The sound builds over time to a single frequency varying from 75 to 105 Hz. By measuring the tone at several locations and on different days, the frequency data shows independence of average particle diameter. This talk will outline recent work at Caltech involving field measurements (including seismic refraction, ground penetrating radar and sand sampling), and will offer an alternative explanation of the desert sounds. [Preview Abstract] |
Sunday, November 19, 2006 9:18AM - 9:44AM |
AG.00004: Granular flows in volcanic environment Lucia Capra Volcaniclastic flows, which include from sediment-water to dry granular flow, are multiphase-system flows that involve some combination of solid, liquid and air. Their behavior in response to applied shear stress is a function of the proportion of these components, grain-size distribution and finally the physical and chemical properties of the solid components. They are generically classified as non-newtonian fluid, from pseudoplasic to dilatant with yield value (generically defined as Bingham fluid). Rheologic threshold can be defined on the base of grain-size distribution. Granular flows (i.e. debris avalanches originated from volcanic collapses) generally contain less than 10 percent in vol. of interstitial fluids which do not constitute a continuous phase in transporting solid fragments. Different mechanisms of granular fluidization have been achieved for such type of flows and particles collision/friction are dominant mechanisms acting during transport. For granular flows less than 1 km3 in volume, the mobility is not directly related with the mass volume and their runout depends on grain-size distribution, clast composition, and type of sliding surface. Textural and morphological characteristics of particles at different flow depths and their variation down-flow are important indicator of the mechanism of emplacement, which can vary from friction to collision-dominated regime. Several examples from Mexican active volcanoes will be here presented. [Preview Abstract] |
Sunday, November 19, 2006 9:44AM - 10:10AM |
AG.00005: Quasi-2D turbulence in bounded domains Herman Clercx In this talk recent laboratory experiments and numerical studies of bounded (quasi) two-dimensional (2D) turbulence will be discussed. The laboratory experiments concern decaying stratified turbulence in square and rectangular containers with emphasis on the self-organization and spontaneous spin-up of the flow. Further analysis of this phenomenon will be provided by results from direct numerical simulations of decaying and forced 2D turbulence. The role of the interaction of turbulence with the no-slip walls and the destabilizing role of the boundary layers, containing large-amplitude vorticity, will be discussed. [Preview Abstract] |
Sunday, November 19, 2006 10:10AM - 10:36AM |
AG.00006: Flushing of a polluted lagoon in Canc\'un, using a SIBEO wave-driven seawater pump Steven Czitrom, Noel Carbajal The coastal lagoon which adorns the seaside resort at Canc\'un, Mexico, is heavily polluted as a result of decades of intense tourist activity development and overwhelmed inadequate planning. The natural flushing time of the lagoon, estimated at 2 to 4 years, is insufficient to cope with the waste that is being dumped and a thick layer of organic matter has accumulated on the lagoon bed. Appropriate legal and sewage treatment measures are imperative to curb further dumping and thus attack the root cause of the problem. This aside, however, the existing situation requires additional technical solutions to restore the ecosystem to a less altered state. A wave and tide driven seawater pump, invented and developed at the National University of Mexico, has been proposed to flush the lagoon with an average 0.2 m$^3$/s of clean and oxygen rich seawater from the neighboring ocean. This flow would reduce the residence time of the lagoon to around 6 months, promoting long term recovery of the ecosystem. The effect and distribution of the pumped water is being studied using a wind and tide driven 3D numerical model of the lagoon hydrodynamics. Some results from this study are presented here. [Preview Abstract] |
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