Vorticity evolution in two-dimensional fluid simulations seeded with random, subsonic velocity fields smoothed with a low-pass filter. Results are shown, in the columns running from left to right, for RBV2, PLUTO, ZEUS, and Stable Fluids, respectively, all on 1024 × 1024 zone grids. The initial vorticity conditions are displayed in the top row, and the middle and bottom rows show the results after ∼20 sound-crossing times of the simulation box. In the top and middle rows, the vorticity color scale is held constant between ﹩\pm 0.01﹩ for all eight simulations. In the bottom row, the color scale is adjusted in PLUTO, ZEUS, and Stable Fluids to ﹩\pm -0.001﹩, ﹩\pm -0.001﹩, and ﹩\pm -0.002﹩, respectively, in order to show the evolution of the fluid vorticity structure. A magnification of a smaller portion of each simulation is shown in the upper left corner of each panel, corresponding to the region encapsulated by the smaller squares shown in the lower right corner of each panel. The simulations took 40 hr, 29 hr, 14 hr, and 22 minutes for RBV2, PLUTO, ZEUS, and Stable Fluids, respectively.