Predictive Engineering and Computational Sciences (PECOS)

The Center for Predictive Engineering and Computational Sciences (PECOS, http://pecos.ices.utexas.edu) at the University of Texas at Austin has openings for Post-Doctoral Scholars and Research Scientists for computational modeling of atmospheric reentry vehicles. PECOS is a research center within the Institute for Computational Engineering and Sciences at UT Austin, and is funded by the department of Energy as part of the Predictive Science Academic Alliance Program (PSAAP).

Applicants are sought with strong background and experience in scientific computing, numerical PDEs, and one or more of the following: computational modeling of high speed (hypersonic) reacting flows, high speed turbulent flows, rarefied and non-equilibrium flows, thermal radiation in participating media, and mechanical and thermal degradation of ablative materials. Experience in large-scale scientific computing, parallel code development, and modern software engineering practices is essential. Applicants must have a Doctorate in Engineering, Science, Applied Mathematics or a related field. Applicants will be considered for Post-Doctoral or Research Scientist positions depending on experience and qualifications, and salary will be commensurate with qualifications. This is a security sensitive position.

To apply for a position, please send via e-mail a cover letter indicating your interest, a current CV and the names and contact information of at least 3 references to Prof. Robert D. Moser at the following e-mail address: reentry_modeling@ices.utexas.edu.

Research Scientists/Associate applicants must also apply at http://utdirect.utexas.edu/pnjobs/ (Job Posting Number 08-02-05-01-0702). The University of Texas at Austin is an Equal Employment Opportunity/Affirmative Action Employer.

The Center for Predictive Engineering and Computational Sciences (PECOS, http://pecos.ices.utexas.edu) at the University of Texas at Austin has openings for Post-Doctoral Scholars and Research Scientists to develop computational algorithms and tools to enable calibration, validation and uncertainty quantification of complex physical models. PECOS is a research center within the Institute for Computational Engineering and Sciences at UT Austin, and is funded by the department of Energy as part of the Predictive Science Academic Alliance Program (PSAAP).

Applicants are sought with strong background and experience in scientific computing, numerical PDEs and one or more of the following: stochastic PDEs, inverse problems, large-scale optimization, model reduction, and Bayesian inference. Experience in large-scale parallel code development and modern software engineering practices is essential. Applicants must have a Doctorate in Engineering, Science, Applied Mathematics, Computer Science, or a related field. Applicants will be considered for Post-Doctoral or Research Scientist positions depending on experience and qualifications, and salary will be commensurate with qualifications. This is a security sensitive position.

To apply for a position, please send via e-mail a cover letter indicating your interest, a current CV and the names and contact information of at least 3 references to Prof. Omar Ghattas at the following e-mail address: reentry_modeling@ices.utexas.edu.

Research Scientists/Associate applicants must also apply at http://utdirect.utexas.edu/pnjobs/ (Job Posting Number 08-02-05-01-0702). The University of Texas at Austin is an Equal Employment Opportunity/Affirmative Action Employer.

Today the National Nuclear Security Administration (NNSA) announced the selection of its five new centers of excellence whose primary focus will be on the emerging field of predictive science. The following five universities will receive $17 million each over a five-year period under NNSA's Predictive Science Academic Alliance Program (PSAAP) agreement:

• California Institute of Technology: The Center for the Predictive Modeling and Simulation of High-Energy Density Dynamic Response of Materials
• University of Michigan: The Center for Radiative Shock Hydrodynamics (CRASH)
• Purdue University: The Center for Prediction of Reliability, Integrity and Survivability of Microsystems (PRISM)
• Stanford University: The Center for Predictive Systems of Multi-Physics Flow Phenomena with Application to Integrated Hypersonic Systems
• University of Texas at Austin: The Center for Predictive Engineering and Computational Sciences (PECOS)

"Since the cessation of underground nuclear testing, NNSA has used simulation and modeling tools and capabilities developed by the Advanced Simulation and Computing (ASC) program to support assessment and certification of our nuclear weapons stockpile," said NNSA Deputy Administrator for Defense Programs Robert Smolen. "ASC's academic alliances have been the training ground where graduate students and post-doctoral researchers gain and hone skills necessary to carry out large-scale simulations."

Predictive science is the application of verified and validated computational simulations to predict the behavior of complex systems where routine experiments are not feasible. The selected PSAAP centers will focus on unclassified applications of interest to NNSA and its three national laboratories: Lawrence Livermore National Laboratory, Los Alamos National Laboratory and Sandia National Laboratories.

The PSAAP centers will develop not only the science and engineering models and software for their large-scale simulations, but also methods associated with the emerging disciplines of verification and validation and uncertainty quantification. The goal of these emerging disciplines is to enable scientists to make precise statements about the degree of confidence they have in their simulation-based predictions.

"We expect the PSAAP alliances will continue to help develop the predictive science field and the workforce of the future, wherein simulations will be pervasive and instrumental in important, high-impact decision-making processes," said Robert Meisner, director of the NNSA ASC program.

For further details on PSAAP, visit http://www.sandia.gov/NNSA/ASC/univ/psaap.html.

Established by Congress in 2000, NNSA is a separately organized agency within the U.S. Department of Energy responsible for enhancing national security through the military application of nuclear science. NNSA maintains and enhances the safety, security, reliability, and performance of the U.S. nuclear weapons stockpile without nuclear testing; works to reduce global danger from weapons of mass destruction; provides the U.S. Navy with safe and effective nuclear propulsion; and responds to nuclear and radiological emergencies in the United States and abroad. Visit http://www.nnsa.doe.gov for more information.

The Institute for Computational Engineering and Sciences (ICES) at The University of Texas at Austin has been selected by the Department of Energy's National Nuclear Security Administration (NNSA) to develop new computer modeling techniques that can provide more reliable predictions of complex systems.

The Center for Predictive Engineering and Computational Sciences (PECOS), a research unit within ICES, will receive $17 million over five years for the project. The university will contribute another $1.7 million to it.

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Benjamin S. Kirk, Adam J. Amar NASA Lyndon B. Johnson Space Center, Aerosciences & Flight Mechanics Division

Atmospheric entry at superorbital speeds involves a number of complex physical phenomena including (i) thermochemical nonequilibrium fluid mechanics, (ii) radiative heat transfer, and (iii) ablative thermal protection system material response. These processes, which are intrinsically coupled, are often treated in a decoupled fashion in engineering analysis and design. This presentation will review the physical processes and governing equations for the aforementioned phenomena, and will discuss the particular challenges which complicate performing predictive simulations. The current approach being used at NASA for the design of the Orion Crew Module will be discussed, with particular emphasis on known limitations of our current modeling schemes. Relevant Orion and historical Apollo design challenges will be reviewed so as to provide motivation for a more rigorous, fully coupled simulation capability which could be used in the future to more accurately model the coupled multiphysics lunar & planetary reentry environment.

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Dr. Rochan Upadhyay, Institute for Infrastructure and Environment University of Edinburgh, Scotland, UK. "Solution of Population Balance Equations using Quadrature Based Moment Methods"

Population balance equations (PBE) were originally developed to describe particulate processes in science and engineering. They now find applicability in a number of applications where stochastic modeling is necessary. PBEs are particularly difficult to solve because, in general, they describe the evolution of a probability density function (PDF) in high dimensional spaces. In this talk, I will describe an efficient computational scheme that evolves only the moments of the PDF without using any assumptions on the form of the underlying PDF. Closure of the moment equations is achieved using Gaussian quadrature. Applications of the technique to select problems in aerosol science, smoke detection, turbulent mixing and combustion will be presented. Results indicate that accurate closure is possible using only a small number of moments. I will also demonstrate that the method can be applied for efficient sampling of a PDF in Monte Carlo simulations of uncertainty propagation and nonlinear Bayesian filtering for real-time system identification applications.

Brief bio: Dr. Rochan R. Upadhyay completed his B. Tech. degree in Mechanical Engineering from the Indian Institute of Technology, Delhi and his M. S. and PhD degrees in Mechanical Engineering from the University of Texas at Austin. His PhD work dealt with the development of a tool for simulating population balance equations using moment methods. At present, he is a research fellow in the University of Edinburgh working in the development of an integrated fire emergency response system for built environments.

Thursday, June 5, 2008 9:30 - 10:30 a.m. ACE 6.304

PECOS/ICES SEMINAR

Dr. Ben Blackwell, Blackwell Consulting, Corrales, NM

One-Dimensional Ablation with Pyrolysis Gas Flow Using a Full Newton's Method and Finite Control Volume Procedure.

Authors: A.J. Amar, B. F. Blackwell and J. R. Edwards

Abstract: The development and verification of a one-dimensional material thermal response code with ablation is presented. The implicit time integrator, control volume finite element spatial discretization, and Newton's method for nonlinear iteration on the entire system of residual equations have been implemented and verified for the thermochemical ablation of internally decomposing materials. This study is a continuation of the work presented in "One-Dimensional Ablation Using a Full Newton's Method and Finite Control Volume Procedure" (AIAA-2006-2910), which described the derivation, implementation, and verification of the constant density solid energy equation terms and boundary conditions. The present study extends the model to decomposing materials including decomposition kinetics, pyrolysis gas flow through the porous char layer, and a mixture (solid and gas) energy equation. Verification results are presented for the thermochemical ablation of a carbon-phenolic ablator which invloves the solution of the entire system of governing equations.

2:00 - 3:00 pm ACE 6.304

Bernard Laub NASA Ames Research Center

September 5, 2008 ACE 6.304 3:30 p.m. - 5:00 p.m.

Ablative materials have been designed to protect structures from intense heating since the earliest days of space exploration, almost 50 years ago. The manned Mercury, Gemini and Apollo reentry capsules all used ablative materials for TPS. These materials are also used as nozzles for solid propellant rocket motors and as heat shields on strategic reentry vehicles (e.g., Minuteman, Trident). All scientific probes to planets and moons with atmospheres employ ablative heat shields. Given the criticality of this technology to both DoD and NASA, it is surprising that no courses are taught at any university in the USA nor is there even one text.

The seminar describes the early approaches employed to model the thermal and ablation response of these materials and how these models evolved through the mid-late 60s. Modeling improvements since then have been incremental. Focus will be on the development of thermochemical ablation models and how such models are used to describe the performance of complex organic resin composites.

Understanding the performance of these materials requires experiments at flight-representative conditions. Arc plasma facilities provide the best simulations of flight environments yet, typically, are unable to simultaneously simulate actual flight parameters (heat flux, pressure, enthalpy, shear, ...). Flight experiments are rarely conducted due to cost. Consequently, traceability between ground and flight can only be accomplished with models that accurately represent materials response phenomenology.

Conducting ground tests of ablative materials in arc plasma facilities is also costly and defining the actual test conditions is, in itself, a challenge. The data that are critical to model development and validation will be discussed.

In conclusion, the status of existing ablative materials is described with particular emphasis on the classes of materials appropriate for specific planetary exploration missions. The requirement for new TPS materials will be discussed.