Deep sea hydrothermal plumes are driven by gravitational buoyancy forces and may rise up to hundreds of meters above their orifice. Ambient ocean water is entrained into the plume during its ascent, which makes the plume diluted and cooled. Long term measurements of physical properties of hydrothermal plumes are limited and are important for understanding heat flow from the Earth’s interior. In Sept 2007 an acoustic scintillation system was used to specifically quantify the temporal variability of the vertical velocity and temperature fluctuations of the hydrothermal plume of Dante at 2155m depth. Six weeks of data was collected and using the space-time coherence of the acoustic amplitude signal, hourly vertical velocity measurements were obtained. Theoretical developments comparing acoustic forward scattering from turbulence and from particles show that suspended particles within the plume produce negligible amplitude fluctuations compared to turbulence modeled by an isotropic and homogeneous Kolmogorov model for the temperature variability.
The vertical velocity and temperature fluctuations show a significant negative correlation with the horizontal flow. The hydrothermal plume of Dante and its interaction with the horizontal flow within the Main Endeavour Field can be generalized as follows: 1) when the horizontal flow is weak (during the ebbing tide), less ambient ocean water is entrained into the plume. In such a case, the plume is faster and hotter and the temperature fluctuations increase within the plume; 2) when the horizontal flow is strong (during the flooding tide), more ambient ocean water is entrained into the plume. In such a case, the plume is slower
and cooler with reduced temperature fluctuations. Results from an integral plume model based on the conservation equations of mass, momentum, density deficit and dissolved tracers and taking into account ambient stratification and horizontal cross flows are compared with observations showing consistent results.
Events Calendar View
-
Departmental Colloquium
Feb 10, 2011
Entrainment and horizontal cross flows and their affect on hydrothermal plume vertical velocity and temperature fluctuations
Guest: Dr. Daniela Di Iorio, University of Georgia, Department of Marine Sciences
Thursday, February 10, 2011 4:00 pm - 5:00 pm
Location: Physics 202 -
Departmental Colloquium
Feb 17, 2011
Non-equilibrium Statistical Mechanics: a growing frontier of “pure and applied” theoretical physics
Guest: Dr. Royce Zia, Virginia Polytechnic Institute and State University, Department of Physics
Thursday, February 17, 2011 4:00 pm - 5:00 pm
Location: Physics 202Founded over a century ago, statistical mechanics (SM) for systems in thermal equilibrium has been so successful that, nowadays, it forms part of our physics core curriculum. On the other hand, most of “real life” phenomena occur under non-equilibrium conditions. Unfortunately, statistical mechanics for such systems is far from being well established. The goal of understanding complex collective behavior from simple microscopic rules (of evolution, say) remains elusive. As an example of the difficulties we face, consider predicting the existence of a tree from an appropriate collection of H,C,O,N…atoms! Over the last two decades, an increasing number of condensed matter theorists are devoting their efforts to this frontier. After a brief summary of the crucial differences between text-book equilibrium SM and non-equilibrium SM, I will give a bird’s-eye view of some key issues, ranging from the “fundamental” to (a small set of ) the “applied.” The methods used also span a wide spectrum, from “easy” computer simulations to sophisticated field theoretic techniques. These will be illustrated in the context of an overview of our work, as well as a simple model for transport.
-
NanoSEC Seminar
Feb 21, 2011
Synthesis and possible applications of some oxides nanostructures
Guest: Prof. Zhengjun Zhang, Department of Materials Science and Engineering, Tsinghua University, China
Monday, February 21, 2011 2:30 pm - 3:30 pm
Location: Riverbend Research South Laboratory AuditoriumMetal oxides nanostructures can be fabricated on substrates by thermal oxidation approach or by glancing angle deposition. The nanostructures synthesized by thermal oxidation are normally single crystalline and exhibited some interesting properties. For example, vanadium oxide nanostructures exhibited very good photocatalytic activity, tungsten oxide nanostructures exhibited excellent field emission properties. By GLAD, the morphology of the nanostructures can be well controlled which is important for applications such as antireflection coatings.
-
Departmental Colloquium
Feb 24, 2011
Computer Simulations of Critical Phenomena and Phase Behavior of Fluids
Guest: Dr. Kurt Binder, Institut für Physik, Johannes Gutenberg Universität Mainz and The Univeristy of Georgia, Department of Physics and Astronomy
Thursday, February 24, 2011 4:00 pm - 5:00 pm
Location: Physics 202Computer simulation techniques such as Monte Carlo (MC) and Molecular Dynamics (MD) methods yield numerically exact information (apart from statistical errors) on model systems of classical statistical mechanics. However, a systematic limitation is the restriction to a finite (and often rather small) particle number N (or box linear dimension L, respectively). This limitation is particularly restrictive near critical points (due to the divergence of the correlation length of the order parameter) and for the study of phase equilibria (possibly involving interfaces, droplets, etc.). Starting out with simple lattice gas (Ising) models, finite size scaling analysis have been developed to overcome this limitation. These techniques work for both simple Lennard-Jones fluids and their mixtures, including generalizations to
approximate models for quadrupolar fluids such as carbon dioxide, benzene etc. and various mixtures, whose phase behaviour can be predicted. A combination of MC and MD allows the study of dynamic critical phenomena, and specialised techniques (umbrella sampling plus
thermodynamic integration) yield the surface free energy of droplets as function of droplet size. Thus, computer simulation has become a versatile and widely applicable tool for the study of fluids. -
NanoSEC Seminar
Feb 25, 2011
Nanoengineered materials: Synthesis, design, functionalization and applications
Guest: Dr. Simona Hunyadi Murph, Savannah River National Laboratory, Aiken, SC, 735-11A, Room 125
Friday, February 25, 2011 4:00 pm - 5:00 pm
Location: Riverbend Research South Laboratory AuditoriumInorganic nanoparticles are inorganic materials in which the particle diameter is in the 1-100-nm regime. If we classify materials according to their electronic properties and assign them either to metals, semiconductors, or insulators, then metals and semiconductors are by far more interesting to contemplate on the nanoscale. Fundamentally, the mean free path of an electron in a metal at room temperature is ~10-100 nm, and one would predict that as the metallic particle shrinks to this dimension, unusual effects should be observed. In the case of metal nanoparticles, optical properties can be tuned extensively by the size, shape, aggregation, and local environment of the particle. For gold and silver, multiple plasmon bands that give rise to visible colors can occur in the visible and into the infrared for various geometries. Quantum dots are inorganic semiconductor nanoparticles that have a diameter in the 1-10 nm range, coincident with their respective excitonic Bohr radii. These materials are highly photoluminescent, resistant to photobleaching compared to organic fluorophores and their bandgap energies are exquisitely
tunable with particle diameter, based on quantum confinement effects.This presentation highlights work from its authors’ laboratories on the synthesis, growth
mechanism, physical properties, reactivity, and applications of silver, gold and platinum nanoparticles and quantum dots. This includes nanomaterials with various designs, geometries and compositions prepared by wet chemical synthesis approaches. These metallic nanoparticles are used as templates for creation of
complex and ordered engineered nanomaterials with tailored and tunable structural, optical and surface properties. This consists of core-shell, nano-peapods, fluorescent, solid or hollow nanocomposites that can be used for a plethora of applications including (bio)chemical sensing, imaging, molecular-scale
electronics, environmental implications and energy production applications. -
Special Colloquium
Feb 25, 2011
Kepler: Nasa’s Search for Habitable Planets
Guest: Mr. Roger Hunter, Project Leader Kepler Mission
Friday, February 25, 2011 7:00 pm - 12:00 pm
Location: Physics 202
Page 18 of 121, showing 6 records out of 723 total, starting on record 103, ending on 108
