This shows a movie of a simulation of the Kelvin-Helmholtz instability. Two fluids moving in opposite directions create shearing motions at the interface between the two fluids. Initial perturbations become unstable and form vortices that ultimately develop high-order instabilities, and may even become turbulent.
Here we show the gas density, with the Adaptive Mesh Refinement (AMR) grid highlighted towards the end of the movie. AMR allows us to 'zoom' into details of the structures and resolve them with high precision.
Same as the previous movie, but this time showing the vorticity structures.
The following two movies show a comparison of a uniform grid (32768^2 cells) simulation (left panel), with the AMR run (32768^2 cells effective resolution) from above (right panel). While some differences are aparent, the AMR simulation captures the main features of the instability reasonably well. The uniform-grid simulation resolves somewhat more small-scale structure of the instability. However, the computational cost is 58,000 CPU hours for the uniform-grid case, versus only 1,600 CPU hours for AMR, which means that the AMR simulation is about 36 times more efficient than the uniform-grid simulation.
The FLASH code was in part developed by the DOE-supported ASC/Alliance Center for Astrophysical Thermonuclear Flashes at the University of Chicago.