[rmz]

I am working on a CFD model to simulate wind loads on buildings. I am using the simpleFoam solver and applying ABL conditions.
I already checked different simpleFoam tutorials and constructed my model based on these tutorials.

I want to simulate all possible wind directions so I chose to change the flow direction by 15 degrees (each simulation); So I have 25 simulations to run.

Since I have a very big Mesh, I don't want to rerun snappyHexMesh every time. so I decided to do a cylindrical domain with blockMesh.

my entire cylinder outer face is considered as 1 patch (named outerRim). I don't have separate inlet and outlet patches. I am applying ABL conditions for U on this patch and zeroGradient for p. (since I am applying "atmBoundaryLayerInletVelocity" on the outer face of the cylinder, this condition is also applied on the faces where the flow exists the domain)
using this model I can use the same Mesh, change the flowDirection every time and run only simpleFoam.

I evaluated my model without the stl files (blockMesh and simpleFoam) and I recognized that i have a weird flow near the exit (image below).

*cylindrical domain: diameter: 6000 m and height: 250 m
-the entire outer face of the cylinder is considered as 1 patch named outerRim (color red in the image).
-in Red: "outerRim" patch
in blue: "top" patch


*U file:


*p file:


*streamLines exiting domain: flow exiting domain with sudden change of gradient.


Because of the weird flow near the exist, I thought my model could be bad and give non realistic results.

questions:
1-should a CFD model have seperate inlet and outlet patches and boundary conditions?
2-is acceptable to apply "atmBoundaryLayerInletVelocity" on the outerRim, so it is also applied on the faces where the flow exists the domain?
3-is my model physically (mechanically) good, and does it give good realistice results?
4-in case my model is good, how can I calibrate it (which boundary conditions to use for the variables) in order to have a smooth ABL wind profile and good results from the simulation?