Upcoming GFDI Colloquia

    2016-03-14 Mark Sussman Seminar

    “An adaptive coupled levelset and moment-of-fluid method for simulating droplet impact and icing on solid surfaces.”

    Dr. Mark Sussman

    Professor of Mathematics

    Florida State University

    Time

    Monday, March 14, 2016 at 1:00PM

    Place

    Melvin Stern Seminar Room

    Room 18 Keen Bldg.

    Refreshments will be served at 12:45PM

    Abstract:

    A new numerical method is presented for simulating droplet impact and icing on solid surfaces. The four materials, air, liquid, ice, and solid are represented using the coupled level set and moment-of-fluid interface reconstruction method. The moment-of-fluid interface reconstruction algorithm has volume and linearity preserving properties using only local information within a computational cell, and for any number of materials. The ghost fluid numerical method has been implemented so that solutions are consistent with the jump conditions at the interface(s) taking into account surface tension, triple point conditions, contact line dynamics, phase change, expansion of ice, and heat release. Results are presented in 2D, RZ, and 3D coordinate systems which demonstrate the effect of surface wetting properties on the resulting drop impact and solidification.

    The presented numerical method is general enough to be applied to many scenarios where materials change phase. An example of the application of the new method to nucleate boiling problems in microgravity environments

    will be presented too.

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    2016-03-23 Cory Barton Defense

    “Spatio-Temporal Evolutions of Non-Orthogonal Equatorial Wave Modes Derived from Observations”

    Speaker

    Cory Barton

    Geophysical Fluid Dynamics Ph.D. Candidate

    Florida State University

    (Major Professor: Dr. Ming Cai)

    Time: Wednesday, March 23, 2016 at 1:00PM

    Place: Melvin Stern Seminar Room Room 18 Keen Bldg.

    Dissertation Defense will follow the seminar

    Abstract: Equatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. The non-orthogonality of wave modes has yet posed a problem when attempting to separate data into instantaneous wave fields where the waves project onto the same structure functions. We propose the development and application of a new methodology for equatorial wave expansion of instantaneous flows using the full equatorial wave spectrum. By mapping the meridional structure function amplitudes to the equatorial wave class amplitudes, we are able to diagnose instantaneous wave fields and determine their evolution.

    The wave class spectra diagnosed assuming the peak projection response depth scale mostly match their expected dispersion curves, showing that this method successfully partitions the wave spectra by calculating wave amplitudes in physical space. This is particularly striking because the time evolution, and therefore the frequency characteristics, is determined simply by a timeseries of independently-diagnosed instantaneous horizontal fields. Vertical tilting in the wave fields is similarly diagnosed across multiple pressure levels. We have confirmed the continuous evolution of the QBO selection mechanism for equatorial waves in the tropical middle atmosphere and additionally identified a time-evolution of the zonal wavenumber spectrum responsible for the amplitude variability in physical space.

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    Upcoming Colloquia at GFDI.

    Check our calendar for related events.

    2016-02-19 Eli Tziperman Seminar

    Title

    “COLD: Snowball Earth ocean circulation, and WARM: suppression of Arctic air formation in warm climates”

    Speaker

    Dr. Eli Tziperman

    Professor of Oceanography and Applied Physics

    Department of Earth & Planetary Sciences

    Harvard University

    Time

    Friday, February 19, 2016 at 2:30PM

    Placce

    Melvin Stern Seminar Room, 018 Keen Bldg.

    Refreshments will be served at 2:00PM

    Abstract:

    Part I: The hypothesized complete freezing of the Earth during the Snowball Earth events of the Neoproterozoic Era (1,000 to 542 Myr) poses several interesting problems, testing our understanding of ocean dynamics in an unusual dynamical regime. An ocean covered by thick ice and driven only by a very weak geothermal heat flux (0.1 watts/m^2) is shown to be surprisingly dynamic, characterized by strong zonal jets, an energetic turbulent eddy field and a dramatic meridional overturning circulation limited to very close to the equator. We discuss the dynamics of the mean zonal jets and meridional circulations, the Lorenz energy cycle and the relevant eddy-generating instability mechanisms.

    Part II: High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable (warm) climates. We study the polar night process of air mass transformation from high-latitude maritime air, to much colder high-latitude continental air. We find that, in warm climates, a low-cloud feedback considerably slows radiative cooling of the surface and amplifies continental warming. This mechanism may explain recent continental warming and indicates that optically thick low clouds could help maintain frost-free winter continental interiors in equable climates.

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