Emptying a hollow object

[48design]

Hi guys,

I try something that seems to be very easy but doesn't work as I expected.
We do have an object, let's say an oiltank. What I try to do is to fill this tank (btw. from the bottom) and after filling it I'm trying to empty this oiltank (through the same opening).
I tried different options but I don't get it to work. Inside the opening is the source object with a positive discharge. To empty the tank I tried a negative value for this parameter,
I also tried to move the source outside the grid (which leads to a complete filling of the tank?!) and some other things but I don't have a solution for this.

By the way I am using PhoenixFD 1.2.

Thank you,
Fabian

[Ivaylo Katev]

Hi Fabian,
the negative discharge should make the trick, but is not enough.
Currently you can't empty the object, because there is nothing to replace the water, you need an air source (a hole for example) like in the real world. Try to disable the wetting, this may help.

[48design]

I didn't expect PhoenixFD being THAT physically accurate.
Thank you, again, Ivaylo!

[Ivaylo Katev]

is it working now? it's not about the physical correctness, i suppose with FT advection it will work without any air source.

[48design]

It is working, although there is lots of turbulence going on in the water now. I think I need to simulate lots of frames and then "time-warp" the animation to fit into my storyboard. I am using forward transfer for advection and still need the air source. I wished I had PhoenixFD2 for this project...

[48design]

Okay... now I have a really strange problem that cost me hours and hours without a solution in sight.
See the attached screenshot. The fluid breaks in two parts while emptying without any reason...

[48design]

So.... it seems that I have fixed this problem with the help of "classic" for advection mode instead of "forward transfer" which I thought is better for liquids. Nevertheless it's strange for me that the liquid changes from one frame to the other from visible to invisble on one part of the liquid.

[Ivaylo Katev]

i suppose this is just the preview settings. the FT advection tends to form compressed liquid, i.e. liquid significantly above 1.
the liquid presets are set to show up to 1.5, so the compressed liquid becomes invisible

[48design]

No, it's also in the rendering. Not just the preview. It really looks like those voxels are just not rendered, but they are used to simulate the fluid behaviour...

[48design]

Now the same problem arises with the "classic" method...

[Ivaylo Katev]

no idea, send us a scene

[48design]

You got mail...

[Ivaylo Katev]

the scene you sent me does not seem to be the same. different geometry and nothing happens

[48design]

The scene I sent you is exactly the same. What do you mean by "nothing happens"?
Please check the file again. It's just a hollow object, some Phoenix sources and one Phoenix simulator.

[Ivaylo Katev]

it looks like this, i tun the simulation until frame 200 and nothing happened, i.e. there was no opening of the hole for emptying the cavity