Flip fluid collapsing in on itself, how can I prevent this?

[nigelgardiner]

Hi There

So I've got a Flip fluid simulation which involves an emitter pouring into the glass.

Everything is as it should be until the emitter stops, (planned) at which point the volume of the flip fluid immediately begins to collapse until it is roughly quarter of the volume it achieved at it's maximum volume.

A total of 1.7mil particles with a particle separation of 0.004 are emitted and I still have 1.7mil particles and the end of the sim so I'm not losing particles.

I have reseeding off.

I've tried increasing the number of solver sub steps but that hasn't helped.

I've tried increasing the number of particles also no difference.

I'm going to try turning reseeding back on and see if that helps but i don't understand why it would be needed if volume is sustained until the emitter stops.

Any advice?

thanks

Nigel.

 

 

[golubevcg]

Have you tried "Apply Particle separation" inside FLIP solver -> Particle Motion -> Separation?

 

[Pazuzu]

10 hours ago, nigelgardiner said:

Hi There

So I've got a Flip fluid simulation which involves an emitter pouring into the glass.

Everything is as it should be until the emitter stops, (planned) at which point the volume of the flip fluid immediately begins to collapse until it is roughly quarter of the volume it achieved at it's maximum volume.

A total of 1.7mil particles with a particle separation of 0.004 are emitted and I still have 1.7mil particles and the end of the sim so I'm not losing particles.

I have reseeding off.

I've tried increasing the number of solver sub steps but that hasn't helped.

I've tried increasing the number of particles also no difference.

I'm going to try turning reseeding back on and see if that helps but i don't understand why it would be needed if volume is sustained until the emitter stops.

Any advice?

thanks

Nigel.

 

 

Unfortunately that's one of the limitations of the FLIP method, the volume loss. As Andrew said a particle separation can help to cont-rarest the volume loss on the system. You can try also to apply some drag forces as soon as the fluid start to settle with some speed or pressure conditions, but that can kill a bit the nice momentum.

For this kind of FX I really miss SPH, but its so slow; So in my case I come around to this problem using a mix between PBD and FLIP/PIC in my microtension tools, this way the volume loss is less noticeable, but still not as good as the SPH method, I really hope that SESI update some of the SPH microsolvers some day!.

I hope that this helps you!

Cheers!

Alejandro

Edited July 6, 2017 by Pazuzu

[Atom]

You can always add a divergence field to add pressure to the fluid. Just remember to turn off Activation on the field or animate the Source Scale value down to zero when you are done filling the glass or it will overflow.

ap_FLIP_Fill_VolumeLoss.hipnc

[nigelgardiner]

Thanks for the advice, appreciated.

I am applying particle separation at the default settings, will try testing higher separation scale values. So is collapsing due to the sphere packing issue?

Thanks for the hip Atom.