Air flowing over a still water body - BC of interface
 

Hi all,

I'm trying to simulate a steady-state case of incompressible air flowing over a still body of water, where there is sunlight that impacts the surrounding ground surface and the water body. My goal is to determine the temperature of the water body.

What is the boundary condition of the interface between the air and the water? It does not make sense to use a wall. Should I be setting the surface to interior?

I am using the solar ray tracer, but no radiation model. I am not interested in the movement of the water body, so there is no need to use VOF.

I would use a coupled wall between the two fluids.

But wouldn't that imply that there is a no-slip boundary condition between two fluids though?