Radiation simulation

Hi

I am trying to simulate the temperature of a piece of paper lying on a surface, both subject to a radiation source (so a thermal CFD analyis).

I made a large cube where the bottom side is the floor and the upper side is the outlet. The 4 vertical sides are inlets with a very low inflow speed (0.01 m/s). The piece of paper (modelled as a solid with the correct properties of paper) is lying on the floor obviously. Radiation heat is hitting the surface and the paper from dead above.

When I try to run the model I get the following error: ''Non-planar inlet boundary condition found <Inlet quad4 Fluid wedge6>'' so I suppose something is up with how I am trying to simulate this problem (multple inlets,...). I ran the exact same problem with only one inlet and it ran fine. The paper and floor got hot but the asymmetry of the inflow kinda ''contaminated'' the result.

Any ideas on how I can solve this?

I am also wondering is there is a better way of solving this problem (so maybe I should use a different model setup)?

I am not really interested in the flow field itself, more about the temperatures and flow field due to the temperatures (I included buoyancy due to Boussinesq).

Any help and advice is appreciated!

Thanks in advance

Toon