Hello, I'm thinking about a natural convection problem where you have turbulent flow on a vertical wall. It's compressible flow, and it's a two-phase problem. You have two boundary layers, one for the air-vapor mixture, and one for the condensate. The question I'm pondering is this: Only water penetrates the liquid-gas interface since the vapor condenses. Usually in single-phase problems, the molecular-based properties of viscosity and thermal diffusivity dominate at the wall, since the eddys aren't present there. In this case, I have fluid flowing through a so-called "wall" (i.e. no-slip boundary conditions don't hold; there's flow through the normal direction to the "wall".). Does that also hold? I'm leaning more toward the interface properties of the mixture being eddy-based, and not just molecular. So, for example, viscosity at the interface= molecular viscosity + turbulent viscosity Is this a viable thought?