Basilisk

Basilisk is free software for solving partial differential equations on adaptive Cartesian meshes that refine automatically only where needed. It is the successor of Gerris, by the same developers, and is used mainly for two-phase flows — waves, droplets, bubbles and breaking free surfaces — as well as environmental and oceanographic flows. You write the simulation in C with Basilisk’s extensions. Suited to researchers and flow engineers. Limitations: there is no graphical interface, installation is from source on Linux or macOS, and you need to be comfortable programming in C.