Projects

Astrophysical scenario: neutrino-driven explosion of a massive star

Simulation: F. Hanke, A. Marek, B. Müller, & H. Th. Janka (MPI for Astrophysics)

Simulation Code: VERTEX (3D Hydrodynamics & Boltzmann neutrino transport)

Visualization approach (E. Erastova & M. Rampp, RZG, 2013):

• main objectives: interactive data exploration, visualization of the dynamics of large-scale hydrodynamical instabilities ("SASI")
• tool: VisIt

References:

• F. Hanke, B. Mueller, A. Wongwathanarat, A. Marek, H.-Th. Janka: SASI Activity in Three-Dimensional Neutrino-Hydrodynamics Simulations of Supernova Cores (arXiv:1303.6269)
  
• Stellar Hydrodynamics at MPA
  

Bird migration ist studied at the Max Planck Institute for Ornithology. Data from GPS loggers carried by birds are correlated with wind and topography data to better understand the migration.

This animated visualization first shows points in 3d space only (i.e. raw data from a GPS logger). The points are then connected to represent the migration path. Then, the underlying topography is added followed by arrows representing the wind field.

The second part of the animation is fully time dependent. The camera follows the bird, and it becomes evident that the bird reacts to changes in the wind field and to the topography.

More information:

• M. Wikelski at the Max Planck Institute for Ornithology
• article on the General Meeting 2012 of the Max Planck Society

Visualization by K. Reuter, RZG.

Astrophysical scenario: neutrino-driven explosion of a massive star

Simulation: F. Hanke, A. Marek, B. Müller, & H. Th. Janka (MPI for Astrophysics)

Simulation Code: PROMETHEUS (3D Hydrodynamics) with simplified neutrino physics

Visualization approach (E. Erastova & M. Rampp, RZG, 2011):

• main objectives: interactive data exploration, visualization of the dynamics of large-scale hydrodynamical instabilities ("SASI")
• 400 x 60 x 120 zones on a non-uniform, time-dependent polar grid, approx. 1000 HDF5 output files a 1 GB
• tool: VisIt

References:

• F. Hanke, A. Marek, B. Müller & H. Th. Janka: Is strong SASI activity the key to successful neutrino-driven supernova explosions? (arXiv:1108.4355)
• Stellar Hydrodynamics at MPA
  

Physical Scenario: Turbulent convection of an electrically conducting fluid or plasma.

Simulation: J. Pratt, W.-C. Müller (Max-Planck-Institute for Plasma Physics)

Visualization: Passive tracer particles and a background field are displayed simultaneously as functions of time. Visualization approach by K. Reuter (RZG) using VisIt.

Challenge

Output from SPH simulations is usually given by point clouds with millions of entities (billions in future), each of which contains local information on physical quantities such as temperature or mass density.  While specialized tools produce visually appealing volume renderings (e.g. SPLOTCH), most state-of-the-art visualization packages fail to handle point clouds properly.  On the other hand, these packages offer a plethora of attractive possibilities for quantitative data analysis of gridded data, e.g., for producing contour plots on arbitrary planes through the simulation domain.

Solution

A code package was developed at RZG to create unstructured grids from SPH point data.  The fast three dimensional Delaunay triangulation provided by qhull is used.  The resulting unstructured grid is written together with the point data in a legacy file format which can be read by applications such as Paraview or VisIt.  A serial domain decomposition technique is implemented to keep the memory footprint of the program low.  Hence, datasets of arbitrary size can be handled.

Cooperation

Klaus Reuter (RZG), Claudia Simion (TUM), Claudio Dalla Vecchia (MPE), Markus Rampp (RZG), Sadegh Khochfar (MPE)

Source code

The code package may be obtained upon request for use on RZG systems.

References

• TMoX group at the Max-Planck-Institute for Extraterrestrial Physics
• project poster by Claudia Simion

Astrophysical scenario: 3D-Simulations of Mixing Instabilities in Type-II Supernova Explosions

Simulation: N. Hammer, H.-Th. Janka, E. Müller (MPI for Astrophysics)

Simulation Code: PROMETHEUS

Visualization approach (M. Rampp, 2009/2010):

• main objectives: exploration, quantitative analysis and visualization of the dynamics and morphology of the nuclear composition
• rectilinear (polar) grids with 500x180x360 zones per timestep
• tool: VisIt ("multi-channel" volume rendering, isosurfaces, 2D-slices)

Results:

• download movie (8 MB mpeg4 avi)

References:

• N. Hammer et al., Three-Dimensional Simulations of Mixing Instabilities in Supernova Explosions, Astrophysical Journal  714 1371 (2010) doi: 10.1088/0004-637X/714/2/1371  (arXiv:0910.5169)
• Press releases How a supernova obtains its shape (MPA), Death of a star in three dimensions (MPG), 05/2010

Astrophysical scenario: Merger of a white dwarf binary system as a Type Ia supernova progenitor

Simulation: R.Pakmor et al. (MPI for Astrophysics)

Simulation Code: GADGET

Visualization approach (E. Erastova, M. Rampp, 2009/2010):

• approx. 2 Million SPH particles per timestep
• tool: Splotch (ray-casting tailored to visualization of SPH data)

Results:

• download movie (1 MB mpeg4 avi)
  

References:

• R.Pakmor et al., Sub-luminous type Ia supernovae from the mergers of equal-mass white dwarfs with M~0.9 M_solar, Nature, 7,  2010
• Press releases "Violent explosions in space" (MPA), "Tanz in die Katastrophe" (MPG)

Astrophysical scenario: Dynamic merger phase of a binary neutron star system

Simulation: A.Bauswein & H.-Th.Janka (MPI for Astrophysics)

Simulation Code: relativistic smoothed particle hydrodynamics (SPH) code by Oechslin et al.

Visualization approach (M. Rampp, 2009):

• approx. 500000 SPH particles per timestep
• tools: Splotch (ray-casting tailored to visualization of SPH data), VisIt

 Results:

• for snapshots and movies see MPA Research Highlight 11/2009

References:

• A.Bauswein & H.-Th.Janka: Are Neutron Stars Strange?, MPA Research Highlight 11/2009
• A. Bauswein, R. Oechslin and H.-Th. Janka, Discriminating Strange Star Mergers from Neutron Star Mergers by Gravitational-Wave Measurements, Phys.Rev.D81:024012, 2010 (arXiv:0910.5169)

Astrophysical scenario: Impact of type Ia supernova on its main sequence binary companion

Simulation: R.Pakmor (MPI for Astrophysics)

Simulation Code: GADGET

Visualization approach (M. Rampp, R.Bruckschen, RZG, R.Pakmor, 2009):

• approx. 9 Million SPH particles per timestep
• tool: Splotch (ray-casting tailored to visualization of SPH data)

Results:

• download movie (2.9 MB mpeg4 avi)
  

References:

• R.Pakmor et al. The impact of type Ia supernovae on main sequence binary companions. Astronomy & Astrophysics 489, 943-951 (2008)
• Emmy Noether Junior Research Group "Type Ia Supernova explosions" at MPA

Physical scenario: study of basic theoretical aspects of turbulence in plasmas in the framework of magnetohydrodynamics (MHD)

Simulation: W.C. Müller (IPP)

Simulation Code: MHD

Visualization approach (S.Malapaka, IPP & R.Bruckschen, RZG, 2008/2009):

• main objectives: exploration, analysis and visualization of massive datasets
• rectilinear (cartesian) grids with 1024³...2048³ zones
• tool: VisIt (parallel ray-casting, isosurfaces, ...)

References:

• Independent Max-Planck Junior Research Group "Computational Studies of Turbulence in Magnetized Plasmas"'

Astrophysical scenario: neutrino-driven explosion of a massive star

Simulation: A.Marek, H.Th.Janka (MPI for Astrophysics)

Simulation Code: VERTEX (Boltzmann neutrino radiation hydrodynamics in 2D)

Visualization approach (M. Rampp, RZG, 2008/2009):

• main objectives: interactive data exploration, visualization of the dynamics of large-scale hydrodynamical instabilities ("SASI")
• 500 x 128 zones on a non-uniform, time-dependent polar grid
• tool: VisIt (parallel ray-casting)

Results:

• download movies

References:

• A. Marek &H.Th. Janka: Delayed neutrino-driven supernova explosions aided by the standing accretion-shock instability. Astrophysical Journal 694, 664 (2009).
• Press Release Cluster of Excellence "Universe" (Feb 2, 2009)
• Stellar Hydrodynamics at MPA
  

Physical scenario: fluctuations in a thermonuclear fusion plasma (tokamak geometry)

Simulation: M.Püschel, F.Jenko (IPP)

Simulation Code: GENE (gyrokinetic turbulence)

Visualization approach (R.Bruckschen & J.Mejia, RZG, 2007):

• main objectives: animation and interactive analysis of time-dependent data sets (3D impression, dynamics), development of a tailored visualization toolkit
• mapping of flux-tube coordinates to real space (torus) sampled by 1280 x 480 x 96 grid points
• out-of-core shader-based method
• point-based pseudo volume rendering
• Java application (JOGL API) for portability

References:

• Helmholtz-University Young Investigators Group "Theory and ab-initio simulation of plasma turbulence"

Astrophysical scenario: thermonuclear deflagration of a white dwarf star

Simulation: F.Röpke, W. Hillebrandt (MPI for Astrophysics)

Simulation Code: SUCCESs (finite volume hydrodynamics + level-set method for thermonuclear burning fronts)

Visualization approach (R.Bruckschen, RZG, 2007):

• main objectives: combined volume rendering of the complete time-dependent dataset
  • stellar structure: scalar density field on the moving, rectilinear 1024³ grid
  • deflagration front: level set renderend as a semi-transparent cloud of points
• out-of-core rendering with hybrid display (point based/volume rendering)
• interactive preview, movie mode with high fidelity transparency

References:

• F K Röpke, R Bruckschen: Thermonuclear supernovae: a multi-scale astrophysical problem challenging numerical simulations and visualization, New Journal of Physics 10, 2008
• Emmy Noether Junior Research Group "Type Ia Supernova explosions" at MPA
• download movie (41 MB avi)

Astrophysical scenario: formation and evolution of structure in the universe

Simulation: V.Springel, S.White (MPI for Astrophysics)

Simulation code: GADGET-2 (cosmological N-body/SPH), ~ 10¹⁰ particles in 3D

Visualization approach (R.Bruckschen, RZG, 2006):

• main objectives: interactive exploration ("fly-through") of individual time-slices at full resolution
• visibility-based out-of-core method using a spatial subdivision scheme
• quantization based on local bounding boxes (low error)
• GPU shader based de-quantification and rendering

References:

• V. Springel et al. Simulations of the formation, evolution and clustering of galaxies and quasars. Nature (2005).

• Galaxy Formation Group at MPA