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iPLEX Meeting

Kraig Winters (UC San Diego)

Stratified Flow Past an Obstacle

Posted on Jun 17, 2013 in GAFD 2013

The laboratory experiments of Browand and Winant (Geophysical Fluid Dynamics, 1972), in which a cylinder is towed horizontally in a uniformly stratified fluid, will be used as a case study in combining laboratory, numerical, and theoretical approaches to idealized flows with geophysical applications. This talk will focus first on the steady, low topographic Froude number regime characterized by blocking, upstream propagation of long gravity waves and stratified hydraulic control. Laboratory and numerical results will be used to motivate a new theoretical framework that describes the observed...

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On the Development of a Scalable Fully-Implicit Stabilized Unstructured FE Capability for Resistive MHD with Integrated Adjoint Error-Estimate

Posted on Jun 17, 2013 in GAFD 2013

The resistive magnetohydrodynamics (MHD) model describes the dynamics of charged fluids in the presence of electromagnetic fields. MHD models are used to describe important phenomena in the natural physical world and in technological applications. This model is non-self adjoint, strongly coupled, highly nonlinear and characterized by multiple physical phenomena that span a very large range of length- and time-scales. These interacting, nonlinear multiple time-scale physical mechanisms can balance to produce steady-state behavior, nearly balance to evolve a solution on a dynamical time-scale...

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Inverse Cascade in Anisotropic Flows

Posted on Jun 17, 2013 in GAFD 2013

We examine the inverse cascade of kinetic energy to large scales in rotating stratified turbulence as occurs in the oceans and in the atmosphere, while varying the relative frequency of gravity to inertial waves, N/f . Using direct numerical simulations with grid resolutions up to 1024^3 points, we find that the transfer of energy from three-dimensional to two-dimensional modes is most efficient in the range 1/2 ≤ N/f ≤ 2, in which resonances disappear. In this range, the cascade is faster than in the purely rotating case, and thus the interplay between rotation and stratification helps...

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Baroclinic Critical Layers and Zombie Vortices in Couette-Taylor Flow

Posted on Jun 17, 2013 in GAFD 2013

We report a new mechanism for creating vortices in a class of flows that are linearly stable and believed, by most researchers, to be also finite-amplitude stable. The vortices should form in stably-stratified Couette flows (both plane and circular), and in protoplanetary disks around forming protostars. Our study was motivated by the fact that protoplanetary disks must have flow instabilities that are capable of transporting angular momentum radially outward so that the protostars can accrete gas and grow into stars. The mechanism that we discovered allows small-amplitude perturbations...

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A Pressurized Cryogenic Nitrogen Cell to Study Rotating Turbulent Convection

Posted on Jun 17, 2013 in GAFD 2013

Due to its fluid properties, cryogenic nitrogen can be used to study flows at high Reynolds and Rayleigh numbers in a compact apparatus compared to standard test fluids. We present the design of a new convection experiment with rotation that uses cryogenic nitrogen, and discuss a few scientific problems that can be addressed with it. The apparatus consists of a 0.5m diameter 1m tall pressure vessel that can hold a pressure up to 35bar, enclosed in a vacuum jacket to improve insulation, and mounted on a rotating table. Several ports on the vessel provide space for different diagnostics and/or...

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Plasma and Liquid Sodium Laboratory Dynamo Experiments at UW Madison

Posted on Jun 17, 2013 in GAFD 2013

First measurements of plasma temperature, density, and flow have been made on the Madison Plasma Dynamo Experiment (MPDX) that allow the particle and energy confinement as well as the plasma conductivity (η) and viscosity (ν) to be estimated. The MPDX is designed to create large flowing plasmas with high magnetic Reynolds number Rm = vL/η >> 1000, and an adjustable fluid Reynolds number 10 < Re = vL/ν < 1000, in the regime where the kinetic energy of the flow exceeds the magnetic energy (MA = v/vA >> 1). Simulations provide scenarios for generating large scale “slow”...

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Low-Dimensional Modeling of Turbulent Convection Roll Dynamics

Posted on Jun 17, 2013 in GAFD 2013

Turbulence is of tremendous importance in a wide range of astrophysical and geophysical flows. Unfortunately, the equations of motion are notoriously difficult to solve. I will introduce an approach to low-dimensional modeling of turbulent flows that focuses on the the large, coherent flow structures which often occur, such as convection rolls in the atmosphere or ocean currents. These structures and their dynamics can be described with relatively few variables using a model consisting of stochastic ordinary differential equations. As a model system to test this approach, we use...

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Horizontal shear in the rotating, stratified ocean : Linear theory and nonlinear evolution

Posted on Jun 17, 2013 in GAFD 2013

Submesoscale instabilities and mixing are poorly understood. We focus our work on barotropic shear with Rossby and Froude numbers of O (1). Instabilities and nonlinear cascades are possible in this regime even though stable stratification is significant. We have demonstrated previously (Arobone and Sarkar, JFM 2012) that the linear stability of the shear layer shows new aspects for strong stratification and moderate rotation rates. In this regime stratification acts to stabilize the inertial instability but greatly increase the range of vertical wavenumbers unstable to barotropic instability...

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Why did the 2010 Eyjafjallajökull volcanic eruption cloud last so long?

Posted on Jun 17, 2013 in GAFD 2013

The global economic consequences of the relatively small Eyjafjallajok̈ ull eruption in the spring of 2010 caught the world off guard. That the eruption cloud lasted for several months rather than weeks, efficiently disrupting air travel and the holiday plans of thousands of Northern Europeans, drew arguably more attention and a certainly garnered a highly emotional response. The unexpected longevity of this eruption cloud was touted to be the consequence of unusual ”perfect-storm-like” weather patterns that also conspired to produce the very dry conditions leading to the massive...

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Conference Announcement: The Present-Day Habitability of Mars

Posted on Sep 26, 2012 in iPLEX Meeting, Mars Habitability 2013

The UCLA Institute for Planets and Exoplanets, The UK Center for Astrobiology and the NASA Astrobiology Institute invite you to participate in a two-day conference in February 2013 that will examine the present-day habitability of Mars. Visit this website for more information: http://planets.ucla.edu/meetings/mars-habitability-2013/ The history of Mars exploration can be characterized by a series of exciting discoveries that have dramatically overturned previously held beliefs about the planet. Until very recently, the dominantly held position within the scientific community was that while...

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IPLEX Ices & Organics in the Inner Solar System Conference Recap

Posted on Jun 22, 2012 in iPLEX Meeting, News

The first IPLEX-hosted conference, titled Ices and Organics in the Inner Solar System, was held in the historic Royce Hall on the UCLA campus on June 12-13, 2012.  The conference was a great success, with more than fifty attendees and twenty half-hour featured presentations that covered a diverse array of topics concerning organics found in the inner solar system. Highlights included several talks on recent work involving water-ice distribution and stability on the Moon, Mars and Mercury and recent results from the Mars Phoenix lander indicating the presence of unexpected salts on the...

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IPLEX Ices and Organics in the Inner Solar System Conference: Preliminary Program

Posted on Jun 3, 2012 in iPLEX Meeting, News

Preliminary Program June 12, 2012 Time Presenter Title of Talk 9:00 Breakfast 9:15 Welcome David Paige and David Jewitt 9:30 Dale, P., Cruikshank Organic Molecules on Saturn’s Satellites: Relationship to Kuiper Belt Objects, Interstellar Dust, and the Solar Nebula 10:00 Ben Teolis Evidence for polar regolith cold trapping of exospheric O2 and CO2 on icy moons Rhea and Dione: A low-temperature analogue to inner solar system volatiles? 10:30 Henry H. Hsieh Ice in the Main Asteroid Belt 11:00 Coffee Break 11:15 Joshua P. Emery Ices and organics on asteroids and...

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iPLEX Conference – Extended Deadline for Abstracts

Posted on May 16, 2012 in iPLEX Meeting, News

iPLEX Conference – Extended Deadline for Abstracts

Abstract Deadline Extension The final deadline for abstract submission for the Ices and Organics in the Inner Solar System Conference has passed, but we are still accepting registrations (i.e you can attend, but cannot give a scheduled talk). The abstract submission form is accessed by registering at the link below. Registration is compulsory and costs $75 (please see logistics page for details of what this cost includes). If you have already registered, you should have received an email with a link to upload abstracts. If you have questions or are having any difficulties, please contact...

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Ices and Organics in the Inner Solar System Conference: Call for Abstracts

Posted on Apr 19, 2012 in iPLEX Meeting, News

Ices and Organics in the Inner Solar System Conference: Call for Abstracts

2nd Announcement and Call for Abstracts On June 12th and 13th, the UCLA Institute for Planets and Exoplanets (iPLEX) will host a two day interdisciplinary conference on the nature, distribution, origin and evolution of frozen volatiles and organics in the inner solar system. Topics will include: • Polar ice and permafrost on planets and asteroids • Delivery of terrestrial planet atmospheres and oceans • Water and organics in comets • Liquid water habitats in the inner solar system The conference format will include summary talks as well as contributed papers, with time set aside for...

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Ices and Organics in the Inner Solar System Conference – June 12-13

Posted on Mar 2, 2012 in iPLEX Meeting, News

Ices and Organics in the Inner Solar System Conference – June 12-13

Water, organics and other volatiles are widely distributed throughout the inner solar system. For example, we find volatiles in the interiors of terrestrial planets and asteroids, as solids in the cryospheres, polar caps and permanently shadowed regions of planets and asteroids, as liquids on the surface of Earth and possibly on Mars, as gases in atmospheres and exospheres and in icy objects recently scattered to the inner solar system from beyond the snow line. Volatiles have played a key role in determining the properties and evolution of inner solar system bodies, and are central to the...

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