Depending on how heavy simulations you want, it’s surprising how light hardware you can get away with in OpenFOAM. I used it for some university courses on a 2012 MacBook Pro (dual booted with Ubuntu) around 2021, and I could run 2D, two-phase simulations just fine.

Of course, if you want to run 3D stuff with large shear forces or turbulence and high time resolution you’re gonna have to grab a veeeery big coffee while you wait. However, the ability to stop and restart the simulation is really nice, and lets you see what’s been simulated so far.