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Flip Narrow Band Particles Hitting Underside Small Scale

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I have set up a simple narrow band flip tank and am dropping a small object (cosmetics bottle) into the tank.

The issue im having is on the first frame that the object collides with the fluid it shoots a bunch of random particles out that escape from the narrow band and then re-collide with the underside of the fluid and cause ripples on the surface that I dont want to create.

The RDB sim is running at a time scale of 0.05 and gravity is the only force in the scene so its moving very slowly.
The time scale for the flip solver is 0.1 to get some splash, but as you can see from the attached photos its not anything crazy.

Can anyone suggest a way to either stop this from happening or kill these particles before they collide with the narrow band?

Im not the most versed at flip so this may be a very quick fix

Appreciate any thoughts or help with this!




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I think this is happening because even though you have a narrow band of FLIP, there's still a big vacuum underneath the layer.

You could reduce your volume bound to the bottom limit of your narrow band, but that's not the best solution either I think. To remove those fast particles you could kill by velocity like
"@speed = length(@v);



or you could use a pop speed limit and clamp the max speed of the particles

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Hi Diego,

Thanks for that reply I tried the pop speed limit and that seemed to work which is great.

I do have one other question while im here, you can see in the screen grabs that there is quite a large space/void between the bottle and the liquid.

Im trying to reduce this and make the liquid hug the bottle more in the beginning and not blow outwards and make this gap.


I tried a number of things like lowering the velocity scale, slowing down the RDB sim to 0.025 (which is only using gravity) and upping the subframes from 10 to 30 in the RDB and upping the subframes in the DOP network, and changing the surface tension and viscosity, but it still happens.

There is no problem with the collision guide and I dont have any sort of surface offset on that either.


This is the sort of splash im aiming for: https://www.youtube.com/watch?v=npAuLi1y5AA

Dramatic but close and not blowing out internally too much. I know my bottle is a different shape to that reference but my sim seems way off and I cant seem to figure out how to lessen that gap.

Any suggestions I would be very welcome!



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For once, your bottle is smooth so it's not gonna have any of those wafer ridges that helps it make some cool splashes.

Besides that you can cheat it by pumping some velocities in the shape that you want the crown splash to be like

That said, that are ton of parameters that come into play to achieve that small scale viscous result, it's not a straight out of the box deal like it might be in RF unfortunately.


Good luck

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Hi Diego

Yeah I have tried adding a mountain to the bottle collider body to give different splashes but the gap of air between the liquid and the bottle still remains?

My main concern here is that I cant seem to adjust anything to lessen the gap that is created between the bottle and the liquid, its as if the collision geometry is much larger than it really is, or the force acting on the liquid is greatly amplified.

But even when I drop the collision force or the time scale in the Flip solver the gap remains but the splashes just get smaller? 

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