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Pancho

Surface tension and viscosity

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Am I the only one who seems to experience flip fluid movement due to surface tension on high viscosity fluids? Viscosity is set to 100.000, object size about 5cm (0.05 units) and tension is set to 1.

The details disappear rather quickly and the surface gets smoother. THis shouldn't happen with such a high viscosity. Can I override the surface tension per particle, since the viscosity changes on a per particle basis? H16 here with the new surface tension in the solver.

 

Cheers
Tom

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Perhaps you could interlink the viscosity and surface tension using custom attributes - Or have the surface tension directly derive from the viscosity or the opposite way - Will post a file later if i get chance! 

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4 hours ago, Pancho said:

 THis shouldn't happen with such a high viscosity.

Based on what?

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Well, if you want to melt something in H16 and it turns into a liquid it shouldn't deform before changing from its solid state into a liquid one. The way to do this a.f.a.i.k. is to use high viscosity and then change it to something lower.

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Do you have a test file that shows this? Simple tests here don't show any movement with high viscosity and surface tension.

 

Surface tension attributes aren't in H16, you should be able to build it though with a GasToParticle and a new field IIRC.

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16 hours ago, marty said:

Do you have a test file that shows this? Simple tests here don't show any movement with high viscosity and surface tension.

 

Surface tension attributes aren't in H16, you should be able to build it though with a GasToParticle and a new field IIRC.

Their are new surface tension control and attributes in H16 within the flip solver itself, how accurate etc it works i dont know but pretty sure it is their 

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11 hours ago, chrisdunham95 said:

Their are new surface tension control and attributes in H16 within the flip solver itself, how accurate etc it works i dont know but pretty sure it is their 

Hmmm - not sure why you think there is an attribute for surface tension, because.. ta da.. there isn't!

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14 minutes ago, marty said:

Hmmm - not sure why you think there is an attribute for surface tension, because.. ta da.. there isn't!

You can control the pressure jump per particle with a scalar field as a factor for the surface-pressure field. Attached is a very raw example of it.

I hope that helps!

Cheers

Alejandro

pp_st.hip

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12 minutes ago, marty said:

@PazuzuBoom! master DOP magician :lol:

Ohhh Man I don't think so!! So much to learn still! DOP context is like a black Hole full of Chaos and Alternate Possibilities! :)

Cheers!!

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17 hours ago, marty said:

Hmmm - not sure why you think there is an attribute for surface tension, because.. ta da.. there isn't!

 this is what i am referring too; 

33kcf28.png

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3 hours ago, chrisdunham95 said:

 this is what i am referring too; 

right - so how do you define that control to have more surface tension in low viscosity vs high viscosity areas?

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Pazuzu's file, slightly modified, would let you drive the surface tension field values based on a point viscosity attribute or whatever. Makes for some interesting shaping by the end! :)

See attached modded file...

--Dave

pp_st_ds.hip

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14 hours ago, marty said:

right - so how do you define that control to have more surface tension in low viscosity vs high viscosity areas?

Im not sure but my point was their is a surface tension attribute in the new h16 :)

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7 hours ago, chrisdunham95 said:

Im not sure but my point was their is a surface tension attribute in the new h16 :)

That Surface Tension control is a 'parameter' - totally different to an 'attribute' in Houdini.

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On 22/06/2017 at 11:54 PM, Dave Stewart said:

Pazuzu's file, slightly modified, would let you drive the surface tension field values based on a point viscosity attribute or whatever. Makes for some interesting shaping by the end! :)

See attached modded file...

--Dave

pp_st_ds.hip

That's super awesome. Thanks Dave and lord Pazuzu... :D you guys are TOP

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On 6/23/2017 at 9:27 PM, marty said:

That Surface Tension control is a 'parameter' - totally different to an 'attribute' in Houdini.

Well, yes and no. It's a field in the flip solver so you can vary it by voxel, like Dave/Pazuzu did above. Conceptually I would regard it to be closer to an attribute than a parameter, even though you would need a spoonful of extra noodle soup to source it from a point attribute.

The name is surfacepressure not surfacetension, but don't let it fool ya ;)

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If you want to find even more details of the amazing surfacepressure implementation in the FLIP solver, look at the second edition of the "Fluid Simulation For Computer Graphics" book!! Is amazing!!! :) 

Cheers!

Alejandro

Edited by Pazuzu
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Here's another version using PopVop/GasFieldVop instead of wrangles... hope it helps clarify the process! Set this up *very* quickly so let me know if I missed anything. Should be able to drive the surfacepressure field directly from the viscosity field, but the values would probably need adjusting in the 'fit' node.

--Dave

pp_st_ds_PopVOPs.hiplc

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8 hours ago, eetu said:

 Conceptually I would regard it to be closer to an attribute than a parameter, even though you would need a spoonful of extra noodle soup to source it from a point attribute.

it's simply a matter of the degree of generalisations and context here.. e.g. hey you call that a number! it actually an element of a field, a scalar, a coordinate, a component, a matrix and a vector. 

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