alt Hacker NewsThis very much depends on the simulation. CFD historically used 64-bit, with extended precision used internal to an extremely small number of poorly conditioned operations, or with very stiff equations; today it's not at all unusual to use single precision or (strategically) mixed precision, depending on the problem. I think the strongest statement you could make about simulation workloads, rather than them "needing" a specific precision, is that they are usually properly analyzed to determine the needed precision, and then run at that precision.
One could argue that the interesting parts of simulation require higher precision. When you are in stable conditions, that's where your intuition might be sufficient already; once you hit those ugly parts then you start requiring as high precision as you can get to have any correlation with reality. Even a simple solar system simulation through gravity interactions has significant drifts in FP64.