Full compressibility treatment vs. Boussinesq buoyancy approximation
 

Hi all,


I am dealing with a vertical flow of a gas in a pipe heated from the wall, with bulk temperature differences from the wall around 100 degrees C.


I have been using a Boussinesq buoyancy approximation in the setting of incompressible flow for the moment, and have my doubts about the solution since most of the heat transfer solvers in OpenFOAM use a subsonic compressible approach.


Does anyone know a rule of thumb for when incompressible approaches with Boussinesq buoyancy terms should be dropped in favor of a subsonic compressible approach? Particularly in terms of highly heated gas.


Thanks!

The Bousinnesq buoyancy approximation is based on a linear exapnsion, therefore can be used only for small magnitude in the temperature variation. You have such a large difference that a compressible flow model should be required.

Hi, gridley2, take a look at paper: The validity of the Boussinesq approximation for liquids and gases, Donald D. Gray et al., 1976. Hope it helps.


Mingming