Filter field ff[] in gfsview

[liuboh...@gmail.com]

Hi guys

I have run the simulation of a droplet impact on the liquid pool in 3d octree mesh, and I was trying to output the pictures via gfsview, and below I'm attaching one of them.

As you can see the image is not very 'clean': a lot of fraction debris is floating around, which is making no sense in terms of physics. I think that is because the very few residual of fraction in this debris slice, where the cell is virtually empty. I was trying to make a filter of fraction field, and I think this is also done in example atomisation.c by the field "ff[]". I did the same thing in my code (picture below as well)

However when I open the .gfs output pictures vis gfsview, and choose "ff[]" inside the bottom of VOF,  gfsview will terminate. The feedback in terminal is:
 
*** Process received signal ***
 Signal: Segmentation fault (11)
 Signal code: Address not mapped (1)
 Segmentation fault (core dump)

I was wondering if there is something in process I did wrong?  Could anyone give me a tip about this problem?

Cheers

Bo

[Shahriar Afkhami]

maybe this would help (from an exchange on Oct. 26: Re: Basilisk equivalent of DropletSums and RemoveDroplet):

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Hi Jose,

I have completed the implementation of the tag() function. The new version includes an example on how to use it here:

http://basilisk.fr/src/examples/atomisation.c#counting-droplets

to compute the volume and coordinates of individual droplets.

Starting from this it should be quite simple to write the Basilisk equivalent of RemoveDroplet.

cheers

Stephane

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<VOF.png><snapshot event.png>

[liuboh...@gmail.com]

Hi Shahriar

Thanks for your reply.

I'm now working on the event of 'DropletRemove'.

While I'm still curious the function of the scalar field "ff[]" in the example 'atomisation.c'? (actually the one cited in your email.).

Cheers

Bo

在 2017年2月21日星期二 UTC+1下午3:55:02，Shahriar Afkhami写道：

[Stephane Popinet]

Hi Bo,

The artefacts your are seing in your display and 'Remove Droplets' are
really two different things.

To remove the artefacts, but keep all the droplets, you should indeed
used the ff[] field as in atomisation.c. As you can see, ff just removes
fractions which are "too close" to zero or one and which are the cause
of the artefacts you see in gfsview. Normally this thresholding can be
done within gfsview, this works when reading files generated by gfvsiew
but not with Basilisk, for some obscure reason. I will not spend time
trying to fix the bug at this point, since gfsview will be rewritten
with Basilisk at some point.

So, to workaround the bug, you need to compute ff[] within Basilisk, as
done in atomisation.c and then also do what is done in the script here:

http://basilisk.fr/src/examples/atomisation.c#running-in-parallel

i.e. replace ff with f in the generated file using 'sed' i.e. use
something like

% sed 's/VariableTracerVOF f/VariableTracerVOF ff/g' < output.gfs >
output1.gfs
% gfsview3D output1.gfs

then gfsview should not crash when displaying the interface for field
'f' and the artefacts should be gone.

cheers

Stephane

[liuboh...@gmail.com]

Hi Stephane

Thank you very much ! I will try following your tips.

Cheers.

Bo

在 2017年2月22日星期三 UTC+1上午9:08:50，Stephane Popinet写道：

[Stephane Popinet]

> then gfsview should not crash when displaying the interface for field
> 'f' and the artefacts should be gone.

Sorry I meant 'for field ff'

Stephane