Water droplet on surface, problems with interface water/air (video / setup included)

silent2608 · November 24, 2015, 19:09

Hi,

I'm new to CFD (I've done several tutorials etc.). Bascially what I'm trying to do is to simulate marangoni convection along a surface in 2D - that's what I hope to achieve eventually anyway.

At the moment I'm battling smaller problems on my way to that goal.

The domain is 5x15mm (2D) completely walled in, VOF 2 phases (air / water), surface tension incl. wall adhesion (90° contact angle).

As you can see in the video and pictures, within 0.35s the water region expands quite a bit. There is no hard line between air and water, which I feel should exist. I have added the complete setup in the pictures, I would appreciate it a lot if someone experienced could glance over it. I feel like there must be some essential error in the setup.

Video: https://www.youtube.com/watch?v=FzzqNcvDeVU

Setup Fluent: http://imgur.com/a/kUXF9

hwet · December 7, 2015, 04:40

Guess you will get a "hard line" only if the mesh is sufficiently fine. If a cell is filled with 0.1 fraction of water how do you expect to see a "hard line".

The same cell is sufficiently small will have a much larger volume fraction of water.

Not sure though, that is just my view on this...

November 24, 2015, 19:09	Water droplet on surface, problems with interface water/air (video / setup included)	#1
silent2608 New Member Join Date: Nov 2015 Posts: 17 Rep Power: 11	Hi, I'm new to CFD (I've done several tutorials etc.). Bascially what I'm trying to do is to simulate marangoni convection along a surface in 2D - that's what I hope to achieve eventually anyway. At the moment I'm battling smaller problems on my way to that goal. The domain is 5x15mm (2D) completely walled in, VOF 2 phases (air / water), surface tension incl. wall adhesion (90° contact angle). As you can see in the video and pictures, within 0.35s the water region expands quite a bit. There is no hard line between air and water, which I feel should exist. I have added the complete setup in the pictures, I would appreciate it a lot if someone experienced could glance over it. I feel like there must be some essential error in the setup. Video: https://www.youtube.com/watch?v=FzzqNcvDeVU Setup Fluent: http://imgur.com/a/kUXF9

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December 7, 2015, 04:40		#2
hwet Senior Member Join Date: Mar 2014 Posts: 375 Rep Power: 13	Guess you will get a "hard line" only if the mesh is sufficiently fine. If a cell is filled with 0.1 fraction of water how do you expect to see a "hard line". The same cell is sufficiently small will have a much larger volume fraction of water. Not sure though, that is just my view on this...