Inviscid and incompressible Navier-Stokes equations in 2D implemented in Julia and compiled to WASM

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I recently made an online demo of the 2D Navier-Stokes equation running in a web-browser.

https://alexander-barth.github.io/FluidSimDemo-WebAssembly/

My kids like to play with it to build dams and other obstacles in the flow which you can do via the mouse :slight_smile:

I took some notes here to get the WASM part to work:

Basically, I allocate all arrays in JavaScript and use the array type from StaticTools.jl (MallocArray). GPUCompiler is used to generate the WASM output. Only a small subset of julia can currently be used this way, but enough for fluid simulations. The upside is that the WASM binary is very small and the demo loads quickly.

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Very impressive!

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Thats a pretty slick demo! Good to see how much you can do already in WASM.

Now if we can somehow integrate this with WGLMakie.jl…

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Yes that would be awesome! But that won’t be for tomorrow… Currently only elementary math operations work. Named tuples worked too because they could be optimised-out after in-lining all function calls.

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What is CPUCompiler? or do you mean GPUCompiler.jl?

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yes, indeed. I corrected the typo. Thanks!
(ironically, nothing runs on the GPU actually).

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Here is another example of the shallow water equations (for example long waves on the surface of the ocean, like tides)

https://alexander-barth.github.io/FluidSimDemo-WebAssembly/ShallowWater/

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That is interesting. Do you know what sort of fakery is involved in transferring the field to the new domain after a hole had been made?

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When you make a hole, the corresponding grid cells are set to zero velocity and zero surface elevation which creates these kind of shock waves that you are seeing to adjust the flow field.

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I was dreaming of some Julia/WASM project like that. Thanks you so much for sharing, I will study your code in detail now :slight_smile: (I hope I can use a similar strategy for my projects too.)

I was about to go to sleep :zzz: Now I cannot sleep. :boom:

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To me the most difficult part is to figure-out how to pass data between javascript and julia… But this example might be useful then.

Yes these waves look a bit hypnotic sometimes :slight_smile:

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