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Computational Astrophysics: Research to Teaching and Beyond Adam Frank University of Rochester A Cast of Many AstroBEAR MHD / Clumpy Flows Sorin Mitran UNC *Andrew Cunningham (UR, UC Berkeley, LLNL) Alexei Poludnenko (UR, NRL) Kris Yirak (UR Grad Student) Jonathan Carroll (UR Grad Student) Thanks to: NSF, DOE, NASA, UR Laboratory for Laser Energetics Simulations: Numerical Experiments with Diff. Eq & PDEs space S (r , t ) S x F ( S ); F , etc t x Initial conditions Boundary conditions space 3rd Age of Simulations: 1st Age: 1-D calculations with computers – CDC 7600, etc 2nd Age: Moderate rez 2-D calculations – Supercomputers: Cray, etc 3rd Age: High rez Multi-D, Multi-physics calc. – Grid Computing, Massively Parallel, Clusters We are talking about “Virtual Reality” on a scientific level. Sim. data sets now as “rich” as real data sets – Petabytes/flops 1015 = one quadrillion bytes. Not just simulation but “Cyberscience” – Integrate IT on all levels of science practice History: Research Simulation Shocked Clumps Woodward 1976 • Astrophysical environments very heterogeneous. • Winds, Blastwaves & ISM are all “clumpy” • Interaction of 1-clump with passing wind is a well studied problem. Critical Parameter tcc: Cloud Crushing Time tcc 2 Rc 1/ 2 Vw c w Frontiers of Algorithm Development Adaptive Mesh Refinement – code automatically places grid cells where needed. Multi-physics – code simulates many physical processes simultaneously – Magnetic Fields, gravity, radiation transport, chemistry, ionization dynamics. UR Computational Group: AstroBEAR Multiyear, Multi grad-student effort Began 2002 Now on 4th generation of student Simulation in Age of CyberScience How to maintain 106 line code base across N years M revisions K Student Generations Static documentation doesn’t work. Our solution: Wiki, selfcompiling documentation Adaptive Mesh Refinement AMR • Different AMR Methods: Grid based regridding Cell based regridding • University of Rochester Code AstroBEAR: grid • Hierarchy of Grids • Require Prolongation/Restriction Operators Carry data from one grid level to another • Prolongation (Corse to Fine) • Restriction (Fine to Corse) R. Deiterding Pre-Planetary Nebula: CRL 618 “Explosion” from dying Solar-type star Mach 10 radiatively cooled bullet AMR grid generation in the system AMR MHD Div B = 0 Hydro: Need conservative prolongation/ restriction operators. MHD: Maintain solenoidal condition. Need divergence free operators on “staggered mesh”. Cunningham et al 2007 Results I MHD Shocked Clump “Standard” Test M = 10 = nc/nw = 10 b=4 Many Clumps: Radiative MHD Shocks in Heterogeneous Media Cunningham et al 2007 M = 10 = nc/nw = 10 b = 10 How AMR Changes Game: Resolution and Convergence Convergence formally defined as approach to known analytic solution. For complex non-linear problem these rarely exist Define convergence as change relative to highest resolution simulation possible. QN QMax f QMax •For adiabatic shock clump convergence appears at N = 120 cells/Rc Resolution and Convergence Radiative Clumps Radiative cooling allows post shock flows to collapse – but how far? AMR allows us to run highest resolution radiative clump simulations to date: N = 1500/Rc Highest resolution radiative clump simulations to date: N ~ 1500/Rc Resolution and Convergence Radiative Clumps Radiative cooling allows post shock flows to collapse – but how far? Increases in resolution show qualitatively new behaviors as Dx < lcrit Resolution and Convergence Radiative Clumps What measures, metrics can we trust at given resolution? http://www.pas.roch ester.edu/~yirak/for adam/vorticities.png Radiative MHD Clumps with Self-consistent Fields How many MHD-AMR Codes Not many AstroBEAR Flash ENZO Orion AMR VAC Athena Computation in Teaching My adventure in E-ed-biz 2000 NSF Career Award AstroFlow – Simulation outreach tool Planetarium asks to buy copy (?!?) Create Truth-N-Beauty LLC with UR E-education digital media company Produce simulation based modules for: McGraw-Hill, Prentice Hall etc Second Avenue Software The e-biz goes it alone 2006 Truth-N-Beauty becomes 2nd Ave What we built Celestial Sphere Phases of Moon Seasons Solar System Builder Planetary Atmospheres Going Beyond Teaching Outreach: Use partners in new media to create interactives for websites. Discover/Astronomy/SciAmerican “Serious Games” – twitch games with a science theme. Going Beyond Teaching Star Formation Conclusions Computation – Advanced AMR/multi-physics codes allow new era of simulation – “Weather vs. Climate”: what to do with Petaflops/bytes Teaching by Simulation – New opportunities if done well (graphics, pedagogy) – New opportunities outside of classroom.