[Gfs-users] RemoveBubbles ?

[Arnaud Antkowiak]

Dear all,

I'm trying to filter out of my simulation tiny drops generated inside a big bubble. While

  RemoveDroplets { start = 1 istep = 10 } T 64

successfully removes tiny bubbles in the liquid, it fails to eliminate tiny drops in the gas.
I chose to identify the gas with T = 1, and the liquid with T = 0.
I tried to add RemoveDroplets { start = 1 istep = 10 } (1-T) 64 without success.

Has anyone any successful experience in removing such droplets ?

Many thanks,

Arnaud

PS: RemoveDroplets { start = 1 istep = 10 } T -2 for example does not solve the issue

--
Arnaud Antkowiak
Institut d'Alembert - Université Pierre et Marie Curie
Tel : +33 (0)1 44 27 26 91 (office) or 7 27 05 (lab)

[Chen, Xiaodong]

Armand,

It works fine for me. I notices that the removing process needs repeating to get it done. You can try "istep=1" to see if that helps.

Cheers!

Xiaodong

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[Arnaud Antkowiak]

Hi Xiaodong,

Thanks for the answer. Tuning istep to 1 unfortunately didn't change anything in my case, but I suspect that RemoveDroplets has trouble eliminating droplets lying on the symmetry axis in GfsAxi. Maybe those are not recognized as connected volumes? Stéphane, could you shed some light on this? (The axis is of "Boundary" type)

I managed however to eliminate these tiny buggy droplets (like sparkles) by strongly lowering the CFL condition :
AdvectionParams { cfl = 0.2 }
This way I can capture all the very violent events ocurring in the pinch-off of a bubble. I think this might be of some help for people looking at similar phenomena, such as drop splashes.

Best,

Arnaud

2011/4/7 Chen, Xiaodong <xche...@mail.gatech.edu>

[Stephane Popinet]

Hi Arnaud,

> I'm trying to filter out of my simulation tiny drops generated inside a big
> bubble. While
>
>   RemoveDroplets { start = 1 istep = 10 } T 64
>
> successfully removes tiny bubbles in the liquid, it fails to eliminate tiny
> drops in the gas.
> I chose to identify the gas with T = 1, and the liquid with T = 0.
> I tried to add RemoveDroplets { start = 1 istep = 10 } (1-T) 64 without
> success.
>
> Has anyone any successful experience in removing such droplets ?

Yes, that is a limitation of RemoveDroplets, it can remove "droplets"
(i.e. T = 1) but not "bubbles" (i.e. T = 0). I can't think of a simple
way of doing this right now.

cheers

Stephane

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[Arnaud Antkowiak]

Thank you Stéphane for this information!

I've updated the wiki page of RemoveDroplets and the discussion page to report this.

See you,

Arnaud

[Stephane Popinet]

Hi Arnaud,

> I'm trying to filter out of my simulation tiny drops generated inside a big
> bubble. While
>
>   RemoveDroplets { start = 1 istep = 10 } T 64
>
> successfully removes tiny bubbles in the liquid, it fails to eliminate tiny
> drops in the gas.

The version of RemoveDroplets in the latest version of Gerris
(2011-05-24) can be used to remove bubbles. See:

http://gfs.sourceforge.net/wiki/index.php/GfsRemoveDroplets

cheers

Stephane

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