Turbulent Natural Convection with Condensation

[womfalcs3]

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?

 

[Achy47]

Hi there,

Thank you for your post. You have raised an interesting question about the behavior of turbulent flow on a vertical wall in a two-phase problem. In this scenario, both the air-vapor mixture and the condensate have their own boundary layers, and the question is whether the eddys at the wall will affect the interface properties of the mixture.

From my understanding, the eddys at the wall will indeed have an impact on the interface properties of the mixture. As you mentioned, in single-phase problems, the molecular-based properties dominate at the wall due to the absence of eddys. However, in a two-phase problem with turbulent flow, the eddys will cause mixing and transport of properties between the two phases. This means that the interface properties of the mixture will not solely be determined by the molecular properties, but also by the turbulent properties at the wall.

In terms of viscosity, the interface viscosity of the mixture can be thought of as a combination of both the molecular viscosity and the turbulent viscosity. The turbulent viscosity will contribute to the overall viscosity of the mixture, and therefore, it is a viable thought to consider it in your problem. Similarly, the thermal diffusivity at the interface will also be affected by the presence of turbulent eddys.

I hope this helps in your research. Best of luck with your natural convection problem!