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.
Thursday, Aug 6, 2015 from 3:30PM to 5PM
Domain Decomposition and Time-partitioned Methods for Flow in Fractured Poroelastic Media
by Ivan Yotov
Professor, Department of Mathematics, University of Pittsburgh
We discuss a computational framework for modeling multi physics systems of coupled flow and mechanics problems. The simulation domain is decomposed into a union of subdomains, each one associated with a physical, mathematical, and numerical model. Physically meaningful interface conditions are imposed on the discrete level via mortar finite elements or Nitsche's coupling. We present applications of the framework to modeling flow in fractured poroelastic media and arterial flows based on Navier Stokes/Stokes/Brinkman flows coupled with the Biot system of poroelasticity. We discuss stability and accuracy of the spatial discretizations and loosely coupled non-iterative time-split formulations. We further study the use of the loosely coupled scheme as a preconditioner for the monolithic scheme and establish a spectral equivalence of the two formulations. A reduced-dimension fracture model will also be discussed.
Hosted by Mary Wheeler
Tuesday, Aug 11, 2015 from 3:30PM to 5PM
Predicting Tumor Growth with Biophysical Models Constrained by in vivo Imaging Data -->>NOTE: Room Change
by Thomas Yankeelov
Professor, Biomedical Engineering, Vanderbilt University
The overall goal of our research program is to develop tumor forecasting methods by integrating advanced imaging technologies with predictive, multi-scale, biophysical models of tumor growth to optimize therapeutic response on a patient-specific basis. To achieve this goal we have divided our efforts into approximately equal parts predictive modeling of tumor growth, development of advanced imaging methods in the pre-clinical setting, and application of those techniques in the clinical setting.
After motivating the problem and briefly summarizing our modeling philosophy, we will highlight portions of each of these three components with a particular emphasis on predictive modeling. We will introduce the salient features of several quantitative imaging methods we routinely use, and then present how these data are used to initialize and constrain a series of progressively more complex biophysical models describing tumor growth and treatment response. Results from both the pre-clinical and clinical settings will be presented. We will conclude with a discussion of how we anticipate these models evolving and the problems they will be used to address.
Hosted by J. Tinsley Oden
Thursday, Aug 13, 2015 from 3:30PM to 5PM
Modeling The Pressure Strain Correlation Under Uncertainties
by Aashwin Mishra
Texas A&M University
The cardinal issues forestalling a better understanding of the turbulence phenomenon are the nonlinearity of the inertial cascade physics and the non-local nature of the action of pressure. In this talk, we focus on analyzing, understanding and modeling the latter, manifested in the pressure strain correlation.
The Reynolds stresses provide an insufficient basis to describe the internal structure of turbulent flows, leading to an inherent degree of uncertainty in predictions using classical turbulence models. We carry out a detailed Dynamical Systems analysis of modal ensembles and individual modes in Fourier space to identify the range of possible behavior and the underlying physics. Based on this insight, Different aspects of the dynamics of pressure are discussed, individually and sequentially, vis-a-vis their amenability to the single point modeling paradigm. Thereon, a set of pragmatic compromises is constituted within the form and the scope of the model to outline a modeling framework. The predictions of an illustrative model are compared to numerical and experimental data while being contrasted against established modeling paradigms.
We conclude by quantifying the uncertainty in the modeling framework. For a spectrum of different states of the mean gradient and the Reynolds stress tensors, we establish the range of this uncertainty for rapid pressure strain closures, identify statistically most likely behavior and their evolution.
Hosted by Robert Moser
Tuesday, Nov 24, 2015 from 3:30PM to 5PM
The Time Dimension, “iIntegrators” and Next Generation State-of-the-Art for First/Second Order ODE/DAE Systems
by Kumar K. Tamma
Professor, Department of Mechanical Engineering; University of Minnesota
Each computational science and engineering simulation, whether it is the analysis of a single discipline or a multi-physics application involving, first or second order system or combination thereof, has its own emphasis and analysis requirements; wishful thinking is that a “wish list” of desired attributes by the analyst to meet certain required analysis needs is desirable. Optimal design developments of algorithms are not trivial; and alternately, how to foster, select, and determine such optimal designs for a targeted application if such an optimal algorithm does not readily exist, is a desirable goal and a challenging and daunting task; not to mention the added complexity of additionally designing a general purpose unified framework – a one size fits all philosophy. Under the notion of Algorithms by Design and the theoretical basis emanating from a generalized time weighted residual philosophy, we have developed under the umbrella of "isochronous time integrators [iIntegrators]" representing the use of the "same time integration framework/architecture", novel designs for first/second order ODE /DAE transient/dynamic systems for the general class of LMS methods . The framework not only encompasses most of the research to-date developed over the past 50 years or so, but additionally encompasses more new and novel schemes and solution procedures with improved physics such as energy-momentum or symplectic-momentum conservation and other optimal attributes with/without controllable numerical dissipation. All formulations within the "iIntegration framework of individual or mixed algorithms and designs" yield the much coveted second-order time accuracy in all kinematic and algebraic variables for ODE’s and DAE’s of any index. Under the umbrella of a single unified architecture, the iIntegration framework is envisioned as the next generation toolkit; and illustrative examples are highlighted as well for computational science and engineering.
Dr. Kumar K. Tamma, is currently - Professor in the Dept. of Mechanical Engineering, College of Science and Engineering at the University of Minnesota. He has published over 200 research papers in archival journals and book chapters; and over 300 in refereed conference proceedings, and conference abstracts. His primary areas of research encompass: Computational mechanics with emphasis on multi-scale/multi-physics and fluid-thermal-structural interactions; structural dynamics and contact-impact-penetration; computational aspects of microscale/nanoscale heat transfer; composites and manufacturing processes and solidification; computational development of finite element technology and time dependent algorithms by design; and development of techniques for applications to large-scale problems and high performance parallel computing environments; and virtual surgery applications in medicine. He serves on the editorial boards for over 20 archival national/international journals, Editor-in-Chief (co-shared) of an online journal, and is the Fellow of IACM, USACM, and the Minnesota Supercomputing Institute. He is the recipient of numerous research awards including the “ICCES Outstanding Research Medal for Contributions to Computational Structural Dynamics, June 2014”; and the "George Taylor Research Award" and selected for the University of Minnesota/Institute of Technology Award for Significant and Exceptional Contributions to Research. He is also the recipient of numerous Outstanding Teaching and other national and university awards. His recent book is titled “Advances in Computational Dynamics of Particles, Materials and Structures”, John Wiley & Sons publication.
Hosted by Leszek Demkowicz