Dear Antonio,

I think that Dirichlet condition (function on the border is given, typically zero velocity) at the border between fluid and solid is relevant only for highly viscous fluids, like oil. For water I typically use Neumann condition (water velocity should have zero velocity component orthogonal to the border), see for example this article:  https://www.researchgate.net/publication/29629917_Tsunami_wave_generation_by_the_eruption_of_underwater_volcano

In Mathematica you can find about it implementation here: https://reference.wolfram.com/language/ref/DirichletCondition.html

I think that if the media on the border has some porosity, then border condition can be more complex. Wave interaction with borders depend on their frequency: in acoustical range they differ from hydrodynamic.

Article Tsunami wave generation by the eruption of underwater volcano

Dear Yuri,

Thank you so much for these suggestions. I will check it out asap. Just to remind that this is a groundwater flow model, so we have a porous media in the border. And it is an excavated mine open pit, so the piezometric head of the groundwater is higher than the topographic height of the pit bottom and hence, producing the upwelling of water.

I will try to find out similarities with the case you suggest in your article.

Best regards

Dear Antonio,

In my article your can only find Newmann condition and the problem where it can work. I do not know exact answer to your question because  never worked with mathematical modelling of porous areas. I think that you should go to physical models where porousity is taken into account in generalized way and to see the condition for velocity of fluid on this border. Due to porousity some fluid can come out but there are different friction forces.