Liquid problems

[Wiltehnik]

Hi everyone.

I use Phoenix for liquid simulations for about one month, and I still have many problems.
I read many of problems on this forum, and found out some new informations.
I had a problem of boiling water surface and found solution to use Classic advection (I used FT), but now I have even more problems, as you can see od those clips:

Here you can see water flow for about 5 seconds, but vessel is not filling any more, it reached maximum very fast and not filling even if liquid is still flowing. Also, when first vessel is turned and liquid pass to the other vessel, some liquid is disappeared.

On this clip, you can see that liquid is coming from nowhere after the source is stopped.

Please help, I tried so many options but I just cant make some very simple liquid animations.


Thanks.

--
Best regards,

Mladen Šašić
3D department
Wiltehnik d.o.o. Sarajevo

[Ivaylo Katev]

the reason for the first scene seems to be incorrect conservation method
about the second one can't say nothing, could you send the scenes to phoenix@chaosgroup.com ?

[Wiltehnik]

the reason for the first scene seems to be incorrect conservation method
about the second one can't say nothing, could you send the scenes to phoenix@chaosgroup.com ?

Thanks for fast answer.

I sent the files to your mail.

You said problem for first scene could be incorrect conservation method, I used Smooth.
Which method do you suggest for this kind of animation?

[Ivaylo Katev]

first, both of your scenes have fully closed boundaries, that is not good. the conservation is too low, i made it 30. i unlocked the spf value (limitits 1-20) and the advection step to be 2.
well, the first scene really makes me crazy. i think there is something about the geometry, when i change your cup with any other geometry it works fine, but with this cup only the FT advection helps. btw, the FT advection always makes the liquid to keep correct quantity.
the second scene deserves more attention. first, switch the rendering surface level to 0.5, now is 0.3 that makes the rest liquid visible.
now about the real problem - the birth of water from the wet surface. of course switching to FT removes any problems with the water quantity , but FT is not suitable here due to the boiling. so, i would suggest to declare the grove as source with some small discharge of air that will dry the rest water.

[Wiltehnik]

first, both of your scenes have fully closed boundaries, that is not good. the conservation is too low, i made it 30. i unlocked the spf value (limitits 1-20) and the advection step to be 2.
well, the first scene really makes me crazy. i think there is something about the geometry, when i change your cup with any other geometry it works fine, but with this cup only the FT advection helps. btw, the FT advection always makes the liquid to keep correct quantity.
the second scene deserves more attention. first, switch the rendering surface level to 0.5, now is 0.3 that makes the rest liquid visible.
now about the real problem - the birth of water from the wet surface. of course switching to FT removes any problems with the water quantity , but FT is not suitable here due to the boiling. so, i would suggest to declare the grove as source with some small discharge of air that will dry the rest water.

I tried your suggestions, it is better but I still have some problems.

I tried different objects in first scene and tried only to fill it.
Now it fills correctly, but after the flow is stopped, water disappear slowly.
They are in the same simulator and use the same source.


Maybe problem is spf value because I just don't understand how it affects liquid behavior (as I could see no one does understand )
I found your old post:

there is an important rule i found playing with liquids in equilibrium - you have to use the SPF limits to control the advection, not the step! in numbers the rule looks like this: 15*SPF*FrameRate*cellsize>=acceleration. this means - you can start from the settings of the paints sample (it satisfied the rule) and doubling the gravity, you need to double the SPF lower limit, doubling the resolution (linear) you need to double the SPF.
the

I would like to understand rule you wrote, but I don't understand what is framerate and acceleration in Phoenix, and how can I use those parameters?
Also, I found somewhere you suggest to lock spf limit, and somewhere to unlock. In which cases do you suggest to lock and which to unlock?

Second scene looks ok now, thanks.


--
Best regards,

Mladen Šašić
3D department
Wiltehnik d.o.o. Sarajevo

[Ivaylo Katev]

Now it fills correctly, but after the flow is stopped, water disappear slowly.

yes, this is common behavior of the classic advection. in the incoming release there is an additional parameter that is used to balance the water level, but with the last official you can try with shots in the dark changing the conservation value.
frame rate - this is the animation frame rate usually 30 frames per sec. the acceleration this is the gravity value measured in the scene units. whatever, i think i found a better rule - set the advection step to 2, start a test simulation, see what is the natural spf value, and if the liquid does not settle well, use fixed spf mode with value above the measured one.

[Wiltehnik]

yes, this is common behavior of the classic advection. in the incoming release there is an additional parameter that is used to balance the water level, but with the last official you can try with shots in the dark changing the conservation value.
frame rate - this is the animation frame rate usually 30 frames per sec. the acceleration this is the gravity value measured in the scene units. whatever, i think i found a better rule - set the advection step to 2, start a test simulation, see what is the natural spf value, and if the liquid does not settle well, use fixed spf mode with value above the measured one.

I hope it is not a stupid question, but how can I measure natural spf value?

[Ivaylo Katev]

the phoenix core has mechanism for adaptive spf value, determined by the advection step (the maximal movement of the fluid). the value calculated by the adaptive mechanism is limited by the spf limits. so, you just need to open the spf limits until the spf value is not clamped.