Fluid inside my object

[hstone2003]

Hi,

I'm busy doing some tests for a shot i need to do. I'm using a sphere object for the test now, but will be a character coming out the water. Issue iIm having is that fluid cells are being created inside the object, but only on the polygons where the normals are facing downwards.
I've attached 3 images, you can see any polygon that has it's normals facing slightly in the negative direction fluid cells seem to stick to it, then begins to fill up from the inside. I then added a edit poly to test it that was the case, I deleted the lower poly's and made sure there weren't any polygons facing down which seems to work (except for the bottom capped poly) 3rd image is just the object rotated to show the same effect. I have added a shell modifier to add thickness and the same effect happens.

Any idea why this would happen or something I'm not doing right to fix this? I have made the sphere a solid object and told it to clear inside. SPF set to about 12. (This is a low res sim but same results when having a higher res sim). Also using the latest nightly 2.2 build.



Thanks
Hayden

[Ivaylo Katev]

i'm not sure what you are trying to do, but first be sure that you interpret the preview correctly. don't forget that by default the preview is set to show the cells with intermediate liquid values. i recommend you to increase the upper preview value above 1 to be sure what is happening or to render the liquid.

[hstone2003]

All I'm trying to do is have the sphere come up out of the water. The Character i'm going to be using is very complex so having these issues with just a sphere is a bit annoying, everything else is working perfectly it's just this little issue. Attached is a render I did the other day as a test. Notice the cells stuck to the sphere just above the water line that keep emitting foam and splashes. I'm going to need this scene to finish off 100% still.

https://www.youtube.com/watch?v=ccrRGqIxcn8

I understand what you mean with the viewport preview, however in this case it seems they are stuck on the surface of the object and then continue to emit splashes and foam for some reason. (Wetting is off as well) Sorry if the clip is shot.

Thanks
Hayden

[Ivaylo Katev]

you mean the fact that some cells remain wet and continue to produce splash?
this is very common annoying effect when dealing with curved objects, usually helps to blow away the liquid turning the object for a moment into weak air source.
this is the worse back draw of the grid solvers that the objects have no smooth surface but it's made of cubes
you can try also an alternative method, instead to blow away the water to use negative discharge, it will absorb the water on the surface. never tried this, but almost sure it will do the trick.

[hstone2003]

Ah ok thanks so much. How would you recommend briefly blowing those cells away?
So sorry for all the questions and I really appreciate all your help

[tsetso]

Hi,
I tried to reproduce your problem, but I was unable to get the same behavior.
Can you send a scene to phoenix@chaosgroup.com
Thanks

[hstone2003]

Ok sent.

Thanks

[tsetso]

You can try unchecking the "Clear inside" in the Phoenix FD properties of the Sphere, but that will only work for the underwater part.

[Ivaylo Katev]

clear inside is for some special cases, for example when you push the liquid by a wall, and the wall must leave dry space behind itself

[hstone2003]

hmm, I did that with my sim I tried last night as it started to look promising, however it seemed to fill up the inside of the sphere as the animation went on. See attached.



Did it work your side after the sphere was out of the water? How far did you manage to sim up to?

I'll test this again tonight and see if it works.
Was just thinking as a quick fix, would I be able to stop the simulation once the sphere was fully out the water. Turn off solid mode and restore the sim again. The fluid cells inside the sphere should then just fall through it.

EDIT: Only saw your edit now. Yeah it worked fine for the underwater part, which is why I tried it last night.

[tsetso]

yep, but I got it working with a negative source

What I did is, I created new Source with discharge: -10, and temperature: 300 and added the Sphere as emitter.
In the Phoenix FD properties of the Sphere, make sure that the "Solid object" and "Clear inside" are checked.

You can take a look at the scene attached below

[hstone2003]

Ah Brilliant thanks so much. Checking the file now.