A Case Study in the Visualization of Supernova Simulation Data

Ed Bachta

Visualization and Interactive Spaces Lab

Overview

Introduction Lagrangian-Eulerian Advection Software Design Results Future Work

A Core-collapse Supernova

Begins with a star of 8+ solar masses Eventually, fusion produces Fe in the core Pressure from fusion loses to gravitation Material falls inward, increasing density Neutrinos radiated at a rate of 1057 /s Strong force halts collapse Remaining material rebounds off the core Shock wave carries material away from the core

Simulation

Doug Swesty & Eric Myra, SUNY Stony Brook Exploring the role of convection Radiation hydro code scales to 1000s of procs 2 spatial dimensions (soon to be extended to 3) 20 groups of neutrinos at different energies

Lagrangian-Eulerian Advection A process for visualizing vector

fields, valid for unsteady flows Noise is advected along the

flow, generating an image as output

Results Single frames portray

instantaneous flow Animations simulate motion of

material in flow

Vector plot LEA

“Lagrangian-Eulerian Advection for Unsteady Flow Visualizaion”

Particles seeded randomly each iteration Backward integration finds upstream cell Color of upstream cell advected forward Results blended temporally with bias toward most recent Jobard, Erlebacher, Hussaini (IEEE Vis & CG 2002 [8:3])

Noise at t-1

v

Lagrangianstep

Eulerianstep

LEA Animated

Applied to velocity Propagation of light and

dark areas indicates direction of flow

Areas where noise remains have near-zero velocities

Software

Vis modules provided by the Visualization Tool Kit (VTK)

LEA filter for VTK developed at the Swiss National Supercomputing Centre

Scripts programmed in Python

Results

Combination of LEA with: Scalar data representations

Via colormaps Via iso-contours

Vector data comparisons Via visualization of dot products

LEA & Scalars

Velocity & Entropy

Shows the development of regions of high entropy in upper convective zones

LEA & Iso-Contours

LEA & Optical Depth

The iso-contour where optical depth = 1 describes the surface of last scattering

Generated for each energy group Our results show that these

contours vary with energy group and evolve along with the shock

12

3

8

LEA & Dot Products

Advective vs. Radiative NeutrinoFlux Radiative neutrino flux

Tendency to propagate outward

Advective neutrino flux Effect of convection

Dot product indicates: “Constructive” flux “Destructive” flux Orthogonal flux

Comparison Over Energy

Comparison of Gradients

Lagrangian multipliers: ∂rf (r) = λ ∂rg(r) Describes a set of points where the iso-contours of f(r)

and g(r) are tangential A positive λ indicates parallel gradients A negative λ indicates anti-parallel gradients Very similar to our dot product analysis

The dot product reveals orthogonal conditions

Entropy & Temp.

Using our visualization scheme, we can see: Where the gradients are || Where they are anti-|| Where they are orthogonal How this relates to the flow

of a vector field

Future Work

Extending the framework to support iteration Developing new visualization techniques Enabling remote visualization

Intended for batch processing Investigating Web Services