Surface wetting with contact angle and embed

[Holger Huck]

Hello Basilisk community,

My name is Holger Huck from DLR Stuttgart, and I am currently working on modeling surface wettability effects in multiphase flow using Basilisk CFD. I have been exploring different ways to incorporate wettability effects in complex geometries, starting with a simpler case of a liquid film on an inclined plane.

I am encountering an issue related to advection when attempting to model surface wettability. The problem arises when I introduce contact angle conditions—the film does not behave as expected, and I observe unphysical distortions or instabilities near the contact line. It seems like the advection scheme is not preserving the interface properly, leading to numerical artifacts. I have attached an image illustrating this issue, where the gravity to the vertical plane is skewed by 68.5° .

My ultimate goal is to describe surface wettability in random packing elements, where liquid films form and interact with the solid surfaces. To build up to this, I started with the inclined plane case to validate the approach.

Has anyone else encountered similar issues with advection and surface wettability in Basilisk? If so, I would appreciate any guidance on how to properly handle contact angles and improve the stability of the liquid film. Any suggestions on numerical schemes or best practices for implementing surface wettability would be highly valuable.

I will provide a minimal code example to reproduce my setup shortly.

Looking forward to your insights and discussion!

Best regards,
Holger Huck

[Holger Huck]

Here the minimal code, it is not exactly the setup from the picture, but very close. 

To see quicker what is happening I have decreased the resolution (never a good idea) and I was told to use dimensionless numbers for the liquid and gas properties, I need to do that aswell. I have included the contact-embed.h I'm using, but I want to say that this is not my code.
Any help or idea is appreciated!