I have been trying to simulate flow across a porous square heated cylinder, subjected to buoyancy. I am using BuoyantBoussinesqPimpleFoam with explicitPorositySource via fvOptions. I have attached the case file for reference. (BlockMesh + TopoSet + SetFields before trying simulation)

Now, I am getting negative lift variation, as per the literature, for solid cylinder (see solid.png in attachment). When I introduce porous cylinder instead of solid, the drag variation remains same, but the lift coefficient values (see porous.png in attachment) jump near zero, which is way off the literture value.

The case that I have attached is at Ri = 0.5 and Re = 40 and the coefficient of lift (average) should be near -1.

I have also attached the lift coefficient variation.

What can be the reason for this variation in Cl values and how can I solve it? I have tried almost all variations in putting the Boussinesq approximation into the code, but nothing seems to work out.

Please help me out. Thanks in advance.

P.S. For images and case vist https://www.cfd-online.com/Forums/openfoam-post-processing/191113-error-coefficient-lift-value-porous-media-buoyancy.html