Visualization Techniques for Discrete Ordinates Method Radiation Transport Cornelius Toole Lawrence Berkeley National Laboratory Jackson State University The LBL Visualization Group Mentor: John Shalf Advisor: Loretta Moore C O M P U T A T I O N A L R E S E A R C H D I V I S I O N

Overview Introduction Objective Visualization Toolkit Fast and Light Toolkit Radiation Transport Discrete Ordinates Method for Radiation Transport Results / Demonstration Conclusion / Outlook

Introduction Part of scientific team to investigate process of radiation transport. Need to investigate physical accuracy of radiation transport algorithms

Radiation Transport What is radiation transport? –Describes interaction of propagating radiation through scattering matter that both absorbs and emits radiation Can lead to an understanding of phenomena like core collapse supernovae and other things that blow up Transport equation

Background Previous work by John Hayes on TSI with LLNL compared FLD ( flux limited diffusion ) & VTEF ( variable Eddington factor tensor ) radiation transport algorithms

Background II Worked with the data created by Douglas Swesty, a physicist and astronomer at SUNY Stonybrook –Member of the Dept. of Energy Terascale Supernova Initiative and NERSC user group Data created by use of discrete ordinates method to solve Boltzmann radiation transport equation DOM has different features from other approximations

Discrete Ordinates Method DOM isn't a mere approximation of Boltzmann –As # of ordinates approaches infinity, solution is more exact More computationally intensive Converges better in optically thick situations unlike VTEF or FLD

Discrete Ordinates Method Better convergence in optically thick situations important Star cores are optically thick

Discrete Ordinates Method DOM algorithms tend to exhibit aberrations called “ray effects” Non-physical oscillations “waves” in fluxes far away from source regions Ray effects are global effects –Radiation transport can only detect local effects “Source in a corner”

Discrete Ordinates Methods Integro-differential form of Boltzmann Transfer Equation Discretization of integration over an angle by quadrature sums times appropriate weights at finite points in interval General Discrete Ordinates Methods Approximation for Boltzmann Equation

Discrete Ordinates Method II Continuous radiation flux Discrete radiation flux

Objective To devise visualization techniques to allow deeper analysis of radiation transport algorithms No existing visual tools to allow this

The Visualization Toolkit Open source visualization application programming interface Implemented in C++ with wrappings for Tcl, Python, & Java Free, fully featured, extensible, good documentation Utilizes pipelined visualization approached

The Fast & Light Toolkit FLTK & FLUID were used to connect UI and VTK pipeline Changes to Visualization Pipeline invoked through callbacks from FLTK widgets

Fast & Light User Interface Designer

Radiation Density Visualization m

Radiation Density Height Relief Map m

Time Derivative of Radiation Density Visualization m

SWSE NWNE Dataset contained 180 x 60 x 4 x 1 x 8 x 8 = 2,764,800 intensities for each of the 501 timesteps Discrete Ordinates Method Visualization

Discrete Ordinates Method Visualization II

Summary Radiation Transport Discrete Ordinates Method Various examples of radiation transport visualization

Acknowledgements My parents My wife My mentor John Shalf My advisor Dr. Loretta Moore Cristina Siegerist Wes Bethel Douglas Swesty

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