[Chilli83]

Hi all

I am working with a HVAC simulation where I have to model 150 persons in a large enclosure but I have some trouble regarding the physics for buoyancy turbulence.

I have defined the buoyancy with a gravity of 0, 0 and –g in x, y and z direction respectively. The reference density for the buoyancy I am using the ideal gas law. When I am setting up the Fluid Model I choose the Shear Stress Transport since I get the benefits of the k-epsilon and k-omega models. Since I am calculating with buoyancy I have the option to activate Buoyancy Turbulence and take Production and Dissipation into account. My question is then if this should be done because I thought that it was already included in the k-epsilon and k-omega turbulence models?

Kind regards
Michael

[Elfoon]

Michael,

You should enable bouancy turbulence production and dissipation unless you are trying to scrimp on compuational resource required. Enabling it will give you greater resolution on the interface between layers etc that might form. It is supposed to be much more accurate.

Elfoon

[Chilli83]

Hi Elfoon

Thanks for your reply. I will activate the buoyancy turbulence for my simulations. It was just because me residuals started to oscilate with increasing magnitude. But this must be due to the mesh is to rough.

Kind regards
Michael

[ghorrocks]

Hi,

In natural convection flows it is quite common to get large scale transient structures even though the boundaries are steady. Often these structures are significant in the total heat transfer/flow field and have to be resolved - therefore requiring a transient simulation with a timestep much smaller than you would initially think.

Glenn Horrocks