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Events & Seminars

Seminars are held Tuesdays and Thursdays in ACE 6.304 from 3:30-5:00 pm, unless otherwise noted. Speakers include scientists, researchers, visiting scholars, potential faculty, and ICES/UT Faculty or staff. Everyone is welcome to attend. Refreshments are served at 3:15 pm.

 

Wednesday, May 16, 2012 from 10AM to 11AM

Integrated Radiation Transport and Nuclear Fuel Performance for Assembly-Level Simulationsby Kevin Taylor ClarnoReactor and Nuclear Systems Division, Oak Ridge National Laboratory

The ability to predict the behavior of nuclear fuel assemblies, at a continuum-scale, during irradiation in an operating reactor poses many significant challenges. This presentation will focus on the computational challenges associated with the recent integration of the Denovo radiation transport code and with the AMP thermo-mechanics solver for high-fidelity simulation of nominal operation in a Pressurized Water Reactor nuclear fuel assembly along with initial simulation results from large-scale simulations on Jaguar/Titan (Cray XT6) at Oak Ridge National Laboratory. This is the first step towards analysis of fuel assembly distortion due to a wide variety of multi-physics simulations and part of the Consortium for Advanced Simulation of LWRs (CASL) and the DOE Nuclear Energy Advanced Modeling and Simulation (NEAMS) programs.

Bio: Kevin T. Clarno earned a Ph.D. and M.S. from Texas A&M University, as well as a B.S. from the Massachusetts Institute of Technology, in Nuclear Engineering. He has been employed in the Reactor and Nuclear Systems Division of Oak Ridge National Laboratory (ORNL) since 2004, after serving as a Naval Nuclear Propulsion Fellow at Bettis Atomic Power Laboratory from 2002 to 2004. Dr. Clarno is leading a multi-institutional team to develop the AMP Nuclear Fuel Performance code, which includes a flexible scientific computing foundation for high-performance computing architectures, for the DOE Office of Nuclear Energy. Dr. Clarno has served as the Principal Investigator for several major ORNL Laboratory-Directed Research and Development (LDRD) and DOE projects, including the development of high-performance computing radiation (Boltzmann) transport codes for nuclear reactor simulation and the integration of the NESTLE core simulator with the SCALE nuclear analysis code system. Dr. Clarno maintains a focus on mentoring the next generation of researchers; he has advised 20 students and post-degree researchers and leads the ORNL Nuclear Science and Technology Interaction Program (NSTIP) in bringing university researchers to provide guest lectures at ORNL. He has served, or is actively serving, on six M.S. or Ph.D. committees at three universities and has co-instructed several courses at the University of Tennessee. Dr. Clarno is actively involved in both nuclear fuel and reactor analysis and the development and improvement in ORNL nuclear analysis software. He has been actively involved in the software development of exploratory coupled-physics solvers, as well as production software in SCALE. He has made contributions in the development and implementation of linear and non-linear methods of accelerating 1-, 2-, and 3-D radiation transport solvers, including CENTRM, NEWT, NEWTRNX, and Denovo. Dr. Clarno has published more than 40 papers in journals, conference proceedings, and technical reports, spanning diverse areas of nuclear science and engineering.

Hosted by Robert Moser

 

Thursday, May 17, 2012 from 4PM to 5PM
ACE 2.302 (AVAYA)

Tradeoffs between complexity and accuracy in nonhydrostatic ocean modelingby Oliver FringerDepartment of Civil and Environmental Engineering, Stanford University

Ocean models make several approximations to the Navier-Stokes equations based on the temporal and spatial scales of motion that can be resolved by the computational grid. Due to limitations in computational power, it will be quite some time before ocean models can capture small-scale turbulent processes related to mixing and dissipation. However, computer performance is now enabling ocean models which havehistorically been hydrostatic to resolve processes in which the nonhydrostatic or elliptic component of the pressure field is important. In this talk I will discuss minimum grid resolution requirements that are sufficient to resolve nonhydrostatic processes in the ocean with a focus on internal gravity waves. Internal gravity waves are unique from a computational perspective because they possess horizontal length scales that span both hydrostatic and nonhydrostatic regimes.

The primary physical effect of the nonhydrostatic pressure in internal gravity waves is frequency dispersion which causes waves of different frequencies to travel at different speeds. However, errors in computing the hydrostatic pressure gradient can lead to erroneous numerical dispersion that mimics the effect of the nonhydrostatic pressure. I will show that in order for this numerical dispersion to be smaller than the physical nonhydrostatic dispersion, the grid resolution, dx, must satisfy dx/h<O(1), where h is the relevant depth scale. This constraint shows that predictions of nonhydrostatic internal gravity waves in coastal domains with three-dimensional nonhydrostatic models require simulations with 100s of millions of grid cells. Solution of elliptic problems of this size are challenging even on today's fastest supercomputers. Therefore, I will discuss the advantages of employing a much faster reduced-order model that, although it eliminates a host of physical processes, the model captures the dominant two-dimensional nonhydrostatic physics more accurately than its fully three-dimensional, nonhydrostatic counterpart.

Short bio: Oliver Fringer is associate professor in the Department of Civil and Environmental Engineering at Stanford University, where he has been since 2003. He received his BSE from Princeton University in Aerospace Engineering and then received an MS in Aeronautics and Astronautics, followed by a PhD in Civil and Environmental Engineering, both from Stanford University. His research focuses on the application of numerical models and parallel computing to the study of laboratory- and field-scale environmental flows to understand the physics of salt and sediment transport in estuaries, internal waves and mixing, and turbulence in rivers. Dr. Fringer received the ONR Young Investigator award in 2008 and was awarded the Presidential Early Career Award for Scientists and Engineers in 2009.

Hosted by Clint Dawson