Strong Vorticity on free-slip surface

[vinhvu1995]

Hi, I am currently simulating the flow through an open channel and the vorticity of the fluid flow on the free-slip boundary seems very strange to me. Could anyone explain to me why the vorticity is so strong?

I’ve attached the images in the google drive link below. This is for a Reynolds number of 500.

https://drive.google.com/drive/folders/1YnYqBMA9_kdecoxN1AGOwXTqHk64Xbkf?usp=sharing

Cheers,
Vinh

• This topic was modified 3 years, 1 month ago by vinhvu1995.

[jonathan]

Hi Vinh,

try to apply a threshold on geometry first in order to remove the material number 0 (ghost-) layer and the vorticity artifact.

At the top of your channel the highest finite velocity in your simulation at the slip boundary cell has a neighboring cell in the ghost layer with zero velocity. This is part of how OpenLB realizes parallelization and some interfaces and nothing wrong with your setup. ParaView calculates the vorticity based on that huge gradient at the top now resulting in what we can see on your pictures. If you have a look at the geometry field in ParaView you will always see the material 0 layer wrapping the entire domain.

Best,
Jonathan

[vinhvu1995]

Hi Jonathan,

Thanks for the reply. I feel kind of silly now haha. I’ve thought my results were incorrect.

Cheers,
Vinh

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