Computational Astrophysics: Research to Teaching and Beyond

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Computational AstrophysicsResearch to Teaching
and Beyond

• Adam Frank
• University of Rochester

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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

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SimulationsNumerical Experiments with Diff. Eq
PDEs
Initial conditions
Boundary conditions
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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

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History Research Simulation Shocked Clumps

• 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
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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.

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UR Computational GroupAstroBEAR
Multiyear, Multi grad-student effort Began
2002 Now on 4th generation of student
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Simulation in Age of CyberScience
How to maintain 106 line code base across N
years M revisions K Student
Generations Static documentation doesnt
work. Our solution Wiki, self-compiling
documentation
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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
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Pre-Planetary Nebula CRL 618 Explosion from
dying Solar-type star
Mach 10 radiatively cooled bullet
AMR grid generation in the system
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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
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Results I MHD Shocked Clump Standard Test
M 10 h nc/nw 10 b 4
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Many Clumps Radiative MHD Shocks in
Heterogeneous MediaCunningham et al 2007
M 10 h nc/nw 10 b 10
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How AMR Changes GameResolution 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.
• For adiabatic shock clump convergence appears at
  N 120 cells/Rc

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Resolution and ConvergenceRadiative 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
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Resolution and ConvergenceRadiative Clumps
Radiative cooling allows post shock flows to
collapse but how far? Increases in resolution
show qualitatively new behaviors as Dx lt lcrit
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Resolution and ConvergenceRadiative Clumps
What measures, metrics can we trust at given
resolution?
http//www.pas.rochester.edu/yirak/foradam/vortic
ities.png
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Radiative MHD Clumps with Self-consistent Fields
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How many MHD-AMR Codes

• Not many
• AstroBEAR
• Flash
• ENZO
• Orion
• AMR VAC
• Athena

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Computation in TeachingMy 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
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Second Avenue SoftwareThe e-biz goes it alone
2006 Truth-N-Beauty becomes 2nd Ave
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What we built
Celestial Sphere Phases of Moon Seasons Solar
System Builder Planetary Atmospheres
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Going Beyond Teaching
Outreach Use partners in new media to create
interactives for websites. Discover/Astronomy/SciA
merican Serious Games twitch games with a
science theme.
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Going Beyond Teaching
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Star Formation
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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.