Injected Fluid Volume increases

[OPKJoe]

Hello everybody,

I am trying to do the following (sounds pretty simple):

I want to inject some liquid into a vitro tube.
Preferably the liquid calms down pretty fast and stays inside the glass.


What I achieve/the result I get:

The liquid is being injected over a few frames.
But it doesn't stop moving as far as I'd like. And even worse: the volume seems to increase even after all the particles have been emitted.
Furthermore I see some artifacts around the liquid even though I defines it as implicit surface and assigned a "collosion mesh".


Attached you can find 3 screenshots of test renderings. I see that there is a lot of small scaled noise on the surface - don't know if this is realistic. I somehow doubt it.
picture 1:
picture 2: at about frame 20
picture 3: at about frame 108 (just lightcache preview)


Some Details about the scene:
- Cell Size: 0,1 mm --> 4.8m cells in total
(the vitro is pretty small - only about 30 mm high)
- dynamics: vorticity checkbox is off, value is 0.3
- conservation: smooth with a quality of 30
- material transfert: classic with 10 steps per frame
- liquid has standard values and strong surface mode enabled (sharpness: 1.0)
- Rendering: implicit surface
- Jittering, steps: 50%
- Isosurface level: 0.15


If necessary I can also provide the scene I guess.

[Ivaylo Katev]

hi,
you cell size is very small and this requires very very high spf, perhaps about 100 or even more.
simulating such a small scale is a hard task, because the movements are extremely fast, there are two ways
- simulate with high spf and wait.
- simulate in wrong scale. in the most cases the final users will make no difference, even more they expect the scale to be wrong, because are get used from another simulation based videos.
you can also get nightly build access and use the flip solver, it is able to simulate at lower spf compared to the grid core. but don't expect miracles, it also will need very high spf if you use physically correct scale.

[OPKJoe]

Thank you for your answer.
Do you have any suggestions of an SPF value that might work?
Anyways, if I simulate at a wrong scale (e.g. 10x) - can I scale it down after simulation to match the scaling of the scene or do the whole scene has to be and stay in wrong scaling?

Thank you in advance.

[Ivaylo Katev]

phoenix has an option in the dynamics panel "scene scale", that is by default 1. just change it to 0.1 and this is all. try to simulate with the current setting, and if still the liquid behaves wildly try with smaller value.

[OPKJoe]

I cannot find that option. Is that only in the nightly builds?
How do I get access to them?

[Ivaylo Katev]

you are right, it's in the nightlies (i'm surprised)
you can workaround it using the global scene scale, but better ask the support for access , beside the scale multiplier you will have the flip solver option, it can be helpful

[OPKJoe]

Hey,
the scene scale worked just fine for my simulation.
I am pretty happy with the results now - except the fact that I am still losing volume after the liquid calmed down.

What may be the reason?
The thickness of the collision geometry is about 50times of the particle grid.
SPF is at 100. Is this still too low?

[Ivaylo Katev]

you can try to use FT advection, it is more conservation friendly, or to increase the conservation quality.

[OPKJoe]

Thank you, worked fine concerning the volume.
New problem:
Even after the discharge value goes down to 0 my source object (circular plane) continously releases a little amount of water.
The only thing I changed is the advection to FT and a little higher conservation quality as suggested.

[Ivaylo Katev]

yes, this is a known and very annoying issue of the grid based solver
i suppose you are using liquid source. it's actually a "preset" of the general purpose source, the one with the barrel icon.
select it, open the max listener and type $.liquidmode=false , press enter
then deselect the source and reselect it again, to cause change of the UI dialog. the new UI dialog has the abilities of the general purpose source, and toy have to animate the temperature channel down to zero one frame before the end of the discharge animation.

[OPKJoe]

Hey, thanks for the tip! unfortunately my source is still dripping.

[Ivaylo Katev]

well, i'm sure after certain tips and attempts we will solve this, because it's very common issue and we had always success beating it, but very probably will be faster if you ask for nightly builds and use the flip solver.

[OPKJoe]

Hey,

thank you.
With the flip solver the fluid stops in time.
But the emission now looks more like it's being sprayed than injected. Any suggestions on how to change it to a more cohesive spurt?

[Ivaylo Katev]

the preview looks really strange, like the spf is very low. the flip solver has an old code that sets the spf to 1, when it's enabled for first time, can you check this? return the higher spf if this is the reason.
and enable the surface tension (set it to 1), for small scale sims it is very important condition
and one more question, what kind of source look you are pursuing, can you show some reference photo?

[OPKJoe]

SPF was still set to 100. I set it down to 1 and back to 100 with no effect.
Surface tension of 1.0 looks much better now. But I am not quite sure if this is detailled enough. The grid size is pretty small but the voxels seem rather big to me.
Scene scale is at 0.1 - is that still good for the flip solver?




I would like to achieve a fluid that is being pipetted into a vitro just like in the following video from minute 1:20 on:
https://www.youtube.com/watch?v=ANstQmxqLgM

Hard to tell, but I think there are almost no splashes.
I was planning to simulate the fluid from the tip of the pipette and do everything inside the pipette with a simple object that I just slice down.