Unexpected velocity profile
 

Hi all. I'm trying to do a validation with fluent, on methane combustion. In the attachments the mesh, temperature and velocity profiles are shown. The paper im comparing to is using a local refinement propietary software, so i just imitated the mesh in ansys meshing. It consists of finer mesh around the expected flame to capture gradients better.

My setting are ENERGY ON, K-E turbulence model, SPECIES-->Partially premixed combustion+Steady diffusion flamelet with GRI MECH. I created a flamelet and also the PDF.

My boundary conditions are all coppied from the actual paper, inlet velocities are 0.1048 for air and 0.2371 for fuel, all in m/s. I setted the outlet to prevent backflow, since i was having issues with eddies, but as of now the eddies disspeared, but the actual problem didnt. My temps are as shown in the paper, and also compositions.

The only thing that i changed is the outer wall temp, to set it as 400K since i am not modelling radiation, and my turbulence intensity, which they do not declare and I estimated around 8-10%.

The validation paper im using is https://doi.org/10.1016/S0010-2180(00)00158-9

The problem im having is that my axial velocity plot seems to slow down. Their results show slower speeds, but not that the flow slows down after the flame. I believe this could have soimething to do with buoyancy forces but cant figure it out. It is noted that gravity is turned on in the right direction.


Any help will be appreciated.