How to Grid the 3mm thick Swirl plate
 

I have problem of heat transfer through a combustor woth 3mm thk swirl plate welded on outer surface, acting like fin. When i am giving a mesh to that sheet volume in Gambit, it took to much time for dense grid. & lower dense grid I can not apply.

Please guide me for the type od grid, which I can apply or guide me about the procedure.

Can size function solve the problem??

Thanks all