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Blocking vs Non Blocking Simulation
#1
Hi,
I am doing a tornado simulation where I have particles rotating around Y axes and emit smoke only. I am simulating only smoke, i.e no fuel. I set smoke bouncy and temperature bouncy to zero, my grid size is 10x192x100. Pls see attached for more simulation settings. Finally note that there is volume axis force that just rotates the smoke around Y axes and and pushes smoke away from Y axes as well.

My question: If I set blocking sides to "none", then the simulation starts as expected, i.e. smoke building up rotating around Y axes for bit , however suddenly the smoke starts to move toward the center of the scene as if there was a pulling force at the center of the simulation that sucks smokes toward it?! However, if I set blocking to "both" this pulling toward the center behaviour does not occur.

I am not sure why this happens and why "blocking" creates this behavior?

Thanks,
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#2
Hello,

Blocking makes boundary solid so nothing can get into the grid or out.
Otherwise it can, so this might be affecting the velocities.
Just make sure that the grid is not too tight around the smoke as that's not good for fluid sim.

Regards,
Kresimir Tkalcec
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#3
Hi,

With further testing, I am noticing a very strange behaviour in the simulation that I cannot understand: in the test case I've described in my first email (i.e. just an emitter, and a rotating field that imitates a tornado vortex), when I initially run the simulation, the effect of the vortex field is obvious (i.e. you can see clearly a rotating smoke), however the more the simulation runs, the less effect of the vortex becomes! meaning, initially all smoke is rotating nicely around the vortex axis (frame 0 to 160), then I get some sort of a steady state (for let's say 60 frames), then around frame 220 smoke slows down as if there is no vortex and the volume of smoke changes shape and gets shrunk and disappear?

Now my question: how to debug this behavior? I've used blocking/non-blocking/field advection/etc. but nothing has changed. Also, I've turned on velocity visualization but the only thing I was able to see clearly is how fast/slow velocity vectors are, but it did not help me much. Logically speaking, I still have the emitter, the vortex, so why at the end smoke disappears and shrink that much?

Thanks in advance,
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