kill particles escaping object

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durty
Posts: 65
Joined: Fri Sep 21, 2007 4:49 pm

kill particles escaping object

Postby durty » Sat Apr 30, 2011 8:32 am

hi,
Problem- An object is filled with fluid and the object is compressing. Some particles from the incompressible fluid are escaping the object .

-Can I kill/filter these particles before or at the moment they escape the object?

-Will a compressible fluid be able to hold itself in a container similar to liquid?

thanks.


Anaxarchos
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Joined: Wed Mar 19, 2008 4:21 pm
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kill particles escaping object

Postby Anaxarchos » Sat Apr 30, 2011 1:56 pm

- Have you already been experimenting with different pressure settings?

- Maybe a kIsolated and a kSpeed deamon could help you when trying to kill the escaping particles.

What about more Substeps?


Just a few words about Compressibility:

In CG, most algorithms are based on Incompressibl flow, basically this means the solver will perform some actions in the background, adapting pressure to make sure the fluid's volume won't change. This is done to maintain the Incompressibility Condition, because otherwise the algorithms for solving the liquids wouldn't work.

In RealFlow standard particles you can put some kind of bias into these calculations by playing with Internal/ External Pressure. In Hybrido, there is the Compressibility parameter to influence this (e.g. Compressibility of 1 will be very good for springy, turbulent water like ocean swells or waterfalls whereas 0.0 is good for a calm lake).

Algorithms for compressible flow are much more complicated, what basically means they will take longer to calculate and are likely to have far more parameters one needs to take into account.

The phenomena of compressibilty are happening mainly on a macroscopic level are are most important to phiyscal disciplines like acoustics, so that's why in CG we can live very good without giving anything yout compressibility.

Even solvers like FumeFX or Maya Fluids, that are basically used for simulateing geseous flow in CG are based on Solvers for incompressible flow.
www.fk-fx.com

nemeru
Posts: 6
Joined: Tue Aug 09, 2011 2:06 pm

kill particles escaping object

Postby nemeru » Thu Aug 25, 2011 7:39 pm

To somewhat get rid of the compression of the particles, I suggest using the Filter daemon, and using the "density" or "force" attributes. I find myself using these very often when I need a sim that isn't physically correct. Once you get your number right ("force greater than ####") you're set to go.

One more thing to that - The attribute will differ from the scale of your sim. i working on a sim right now, having it around 3 by 5 by 5 meters, and working with numbers along 2000-2500.

hth


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