Seminars are held Tuesdays and Thursdays in POB 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.
ICES Seminar-Babuska Forum Series
Friday, Feb 27, 2015 from 11AM to 12PM
A solution strategy for the Boltzmann equation: Motivated by physics but not a slave to it
by Philip Varghese
"For those new to the CSEM program, the Babuska Forum is a seminar series started by Professor Ivo Babuska several years ago to expose students to interesting and curious topics relevant to computational engineering and science with technical content at the graduate student level (i.e. the focus of the lectures is on main ideas with some technical content). Seminar credit will be given to those students who attend the forum (We will put out a sign up sheet).
Slides for the seminars may be accessed at: http://users.ices.utexas.edu/~babuska/babuska_forum/index.html."
ASE-EM Department, UT Austin
I will provide a brief review of our strategy to obtain numerical solutions of the Boltzmann equation in gas dynamics that was originally developed as a strictly numerical method. However, the need to incorporate additional physics, like molecular internal energy, that are essential for practical engineering problems led us to reinterpret our solution strategy as a Monte Carlo method with fixed velocity variable weight particles. I will outline my personal view that modern direct simulation Monte Carlo (DSMC) methods are unnecessarily hampered by the current insistence on attributing direct physical significance to simulation particles and will speculate on how the DSMC technique could be made much more powerful and efficient by recognizing that the simulation particles are merely mathematical models.
Hosted by Hamidreza Arabshahi
Tuesday, Mar 3, 2015 from 3:30PM to 5PM
Real-time In-situ Seismic Imaging with Sensor Networks
by WenZhan Song
Professor, Department of Computer Science, Georgia State University
The seismic imaging process today involves massive seismic data collection from hundreds and thousands of seismic sensors to a central place for post computing. The whole process is expensive and often takes days even months to complete. There is great demand for real-time as it would reduce the costs and risks of E&P and mitigate the environment concerns. This talk presents an innovative Real-time In-situ Seismic Imaging (RISI) system that can compute the 3D subsurface imaging in seconds. The RISI system is a mesh network of seismometers that sense and process seismic signals, and compute 3D tomography in-situ in real-time. Instead of data collection then post processing, the mesh network performs the distributed data processing and tomographic inversion computing under the severe bandwidth and resource constraints, and generates an evolving 3D subsurface image as more events arrive. Several innovative distributed tomographic computing algorithms based on travel-time tomography principles have been successfully developed and validated using both synthetic and real-world seismic data set. The hardware prototype system has also been implemented and can be extended as a general field instrumentation platform, to incorporate new geophysical data processing and computing algorithms, beyond seismic.
Dr. WenZhan Song is a Professor of Computer Science and Director of Sensorweb Research Laboratory at Georgia State University. His research mainly focuses on cyber-physical systems and computing for geophysical imaging, smart grid and smart health, where decentralized sensing, computing, communication and security play a critical role and need a transformative study. Dr. Song has led several major interdisciplinary research projects on those issues with $7 million+ grant support (with funding ratio near 90%) from NSF, NASA, USGS, and industry since 2005, and his work on volcano monitoring sensor network was featured in MIT Technology Review, Network World, Scientific America, New Scientist, National Geographic, etc. Dr. Song is a recipient of NSF CAREER Award (2010), Outstanding Research Contribution Award (2012) by GSU Computer Science, Chancellor Research Excellence Award (2010) by WSU Vancouver. He was also a recipient of 2004 National Outstanding Oversea Student Scholarship by China (only 40 in USA) during PhD study. Dr. Song serves several premium conferences and journals such as IEEE Transaction on Parallel and Distributed Systems.
Hosted by Sergey Fomel
ICES Seminar - ICES Student Forum Series
Friday, Mar 6, 2015 from 11AM to 12PM
Representing model inadequacy: A stochastic operator approach
by Rebecca Morrison
"The ICES Student Forums are presentations given by current students in the CSEM program to their peers. The aim of the forums is to expose students to each other's research and encourage collaboration. Seminar credit will be given to first and second year CSEM students."
ICES, The University of Texas at Austin
We investigate model inadequacy of a reaction mechanism model for hydrogen combustion. In a typical reaction, the complete mechanism is either not well-understood, or too complex to effectively use as part of a larger combustion problem, necessitating a reduced model. To account for the discrepancy between the full model and its reduced version, we propose an additive, linear, stochastic operator. This representation is encoded in a random matrix, whose entries are calibrated using a hierarchical Bayesian scheme. In particular, this formulation is designed to respect certain physical constraints, but also be flexible enough to apply to multiple reactions.
Tuesday, Apr 7, 2015 from 3:30PM to 5PM
High-Order Methods for Turbulent Flow Simulations on Deforming Domains
by Per-Olof Persson
University of California at Berkeley
It is widely believed that high-order accurate numerical methods, for example discontinuous Galerkin (DG) methods, will eventually replace the traditional low-order methods in the solution of many problems, including fluid flow, solid dynamics, and wave propagation. In this talk I will present some of the recent developments in our work on efficient and robust DG schemes for real-world problems with deforming domains. Topics include high-quality unstructured curved mesh generation, high-order compact and sparse numerical schemes, artificial viscosity based stabilization of underresolved features such as shocks and turbulence models, scalable preconditioners for parallel iterative solvers, and implicit-explicit schemes for the partitioning of coupled fluid-structure interaction problems. The methods will be demonstrated on important practical problems, including the inverse design of energetically optimal flapping wings and large eddy simulation of vertical axis wind turbines.
Hosted by Tan Bui-Thanh
Tuesday, Apr 14, 2015 from 3:30PM to 5PM
Spiraled Boreholes: An Expression of 3D Directional Instability of Drilling Systems
by Emmanuel Detournay
Department of Civil, Environmental, and Geo-Engineering, University of Minnesota
Occurrence of borehole spiraling is predicted by analyzing the delay-differential equations governing the propagation of a borehole. These evolution equations for the borehole inclination and azimuth are obtained from consideration involving: (i) a bit/rock interaction law that relates the force and moment acting on the bit to its penetration into the rock; (ii) kinematic relationships that describe the local borehole geometry in relation to the bit penetration; and (iii) a beam model for the bottom-hole assembly (BHA) that can be used to express the force and moment at the bit from the external loads applied on the BHA and the geometrical constraints arising from the stabilizers conforming to the borehole geometry. The analytical nature of the propagation equations makes it possible to conduct a systematic stability analysis in terms of a key dimensionless group that controls the directional stability of the drilling system. This group depends on the downhole weight on bit (WOB), on properties of the BHA, on the bluntness of the bit, and on parameters characterizing its response. The directional stability of a particular drilling system can be assessed by comparing the magnitude of this group with a bifurcation value that depends only on the BHA configuration and the bit walk. If this dimensionless group, which depends on the actual drilling conditions, is less than the bifurcation value, the system is directionally unstable, and borehole spiraling is likely. Stability curves for an ideal BHA with two stabilizers are shown to depend on the bit walk, which tends to enhance conditions for spiraling. An application to a field case is discussed. Simulations conducted by integrating the equations of borehole propagation also are presented. They illustrate that, for unstable systems, the model predicts spiraled boreholes with a pitch comparable to what is observed in the field.
Dr Detournay joined in 1993 the Department of Civil Engineering of the University of Minnesota, where he is now the Theodore W Bennett Chair in Mining Engineering and Rock Mechanics. Prior to joining the UMN, he was Senior Research Scientist at Schlumberger Cambridge Research in England. His expertise is in Petroleum Geomechanics, with two current focuses: drilling mechanics (bit-rock interaction, self-excited drilling vibrations, directional drilling) and mechanics of fluid-driven fractures (asymptotic analysis, scaling, numerical modeling).
Hosted by Greg Rodin