Hi

I have a case where methan is release in 33m height. It is only a case of dispersion of methan in the lower atmosphere. However the methan plume aproaches the ground level instead of being stratified inside the lower atmosphere. The uaing a ideal gas formulation of methan, O2 and N2 witha reference density of 1.23 kg/m3 (12 C temperature). I am using CFX5

Can anyone give me a hint of what I am missing in my modelling approach ?

Thanks in advance.

Regards

Jens

Buoyancy should be on, with a gravity vector set.

Make sure your diffusivity for the methane mass fraction is correct. The diffusion should balance the buoyancy and stratify. If the diffusivity is relatively low, the stratification layer will be compressed.

Jeff