I am trying to simulate air-flow around a 5-by-5 array of buildings such that surrounding buildings are urban square blocks and the central building is a tall building (square tall building with fins attached to the corners; these fins have no thickness). The geometry was created in AutoCAD 3D and Design modeler and the Part creation and Mesh creation was done in ICEM-CFD.

As can be seen from the attached image, I have created parts for the surfaces of all 4 corner fins, namey, Fin-1, Fin-2, Fin-3 and Fin-4. I initialized the block as 3D block by selecting the whole geometry and then by using the top-down approach, I decomposed the block and performed needful associations. However, kindly note that I did not create any separate surface blocks on the fins; even when I tried by selecting the vertices of the adjacent air block, ICEM didn't create surface blocks as blocking was already initialized as 3D. However, upon generating the mesh by using Pre-mesh sizing method, I found out that neither ICEM-CFD generated any mesh on the fin surfaces, nor is the ANSYS Fluent reading these surface bodies (or Fins)or for that matter the mesh that I tried to generate on them.

If anybody can help me identify the possible mistake that I have been doing, I would be deeply grateful. I am attaching the images of geometry, parts created in ICEM, blocks created in ICEM, mesh generated in ICEM and the images of surfaces and mesh in Fluent.