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Lecture 20: Fluid Simulation (22)
ld184

what is the inspiration behind constrain divergence to be zero by projection? I'm struggling to understand this. Does this capture the "incompressible" property?

mooreyeel

what even is an incompressible fluid? wouldn't they just turn into gas or something. What is it's applications

jonathanlu31

I think the idea is that since divergence represents net fluid flow, if divergence is zero, that means the rate of fluid that enters a given volume is the same as the rate that leaves. So then you can't store an increasing amount of fluid in the same space, i.e. you can't compress it. Also, I believe gases are considered fluids and would be an example of a compressible fluid. There was another comment from sberkun a few slides ago that mentioned most liquids are incompressible.

rheask8246

@mooreyeel, an incompressible fluid is one whose volume and density do not change even as pressure changes. For example, water is a pretty incompressible under normal conditions.

starptr

^ adding onto rheask8246, most liquids can be modeled as incompressible fluids, and vice versa: most cmopressible fluids are gases. You can ignore the compression factor for liquids in most scenarios since the compression amount is negligible, under normal conditions.

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