Why are fluids in Phun so spongy, and can we get incompressible fluids?!
It is rather difficult to model and simulate incompressible fluids. For most practical situations, water can be considered to be incompressible. This means that no matter how much pressure you put on water, the fluid body still resists to change its volume. Incompressibility is actually related to the sound velocity of a fluid (1500 m/s for water), and in order to achieve incompressibility we would have to use a time step that allows us to resolve fluctuations (sound waves, that is – pressure waves) with this speed. Phun typically runs well below 100Hz which means that the time step is 1/100 s or larger, and this only gives stable simulations if the sound speed is set to a fraction of the real sound speed. We need 50-100 times faster computers to simulate incompressible fluids. However, we’re researching into totally new models for fluid simulations new seen before, so stay tuned!
