HEDSA Webpage Contribution

If you would like to visit the WiSTL homepage click here, or if you would like to learn more about the high energy density science association, click here.

The following image appears on the HEDSA webpage and shows the volume fraction (top half) and density (bottom half) from a numerical experiment where an initially spherical helium bubble has been subjected to a planar shock wave and undergone a significant amount of deformation.

Numerical Simulation

Jeff Greenough (LLNL) has graciously made available the RAPTOR code for these studies.  The planar shock wave moves in the positive y-direction as shown in the computational domain on the right.  Quarter-symmetry is assumed in this 3D simulation and O and R represent a outflow and reflective boundary conditions, respectively.  A Cartesian mesh is employed with 2 levels of adaptive mesh refinement (each have a refinement of 4 to 1), and at the finest resolution level, the bubble radius has 100 cells.  There are approximately 107 cells in the domain and the computation takes 17 hours on a high performance supercomputer using 512 processors.

A light (helium) spherical bubble is initially at rest in the nitrogen domain and is impulsively accelerated by a M=2.95 planar shock wave.  The interaction of the shock wave with the bubble results in baroclinic vorticity deposition on the interface due to misaligned pressure and density gradients.  The shocked bubble image is from a time 700 ms after the shock wave has first reached the upstream pole of the bubble.  A majority of the He is confined to the primary vortex ring (shown as the light blue region in the density image) while a much smaller fraction has been spun off downstream forming secondary and tertiary vortex rings that lag behind the primary by several initial bubble diameters.  These numerical experiments are complementary to laboratory experiments we are actively engaged in.