1. Why is there a limit of 501
1. Why is there a limit of 501 iterations on the AMG and 5001 on the ICCG solvers? Is this is a known and fixed constraint?
2. For nonconformal structured block meshes, does increasing the number of nonorthogonal correctors really help? What is the ballpark percentage limit (as reported by checkMesh) beyond which nonorthogonal correctors are absolutely necessary. Is it 25%, 50%, 75% ?? 3. In the liddriven cavity case, dirichlet boundary conditions are prescribed for the stationary walls. Quoting from F & P: "At a wall the noslip boundary condition applies, i.e. the velocity of the fluid is equal to the wall velocity, a Dirichlet boundary condition. However, there is another condition that can be directly imposed in a FV method; the normal viscous stress is zero at a wall." Is this implicitly done in the OF solvers? If that is the case, then the zero value dirichlet boundary conditions specified in the subdirectory 0/U should apply to the continuity equation? Please excuse my naiveness. Any thoughts/corrections are much appreciated. Thanks! 
Answering my own question. I'm
Answering my own question. I'm sure it will be useful for other n00bs like myself:
1. Possibly because a wellposed problem (proper BC and/or discretization) should definitely not require more than that many iterations. How do I know this? After fooling around with all kinds of meshes for the flow past a bluff body, I have concluded that the time invested on proper meshing is well rewarded. Case in point, when I tried to reduce the mesh size by introducing nonconformal blocks into my domain giving a mesh size of approximately 1 million cells, I also introduced more problems for the solvers. As a result, most of the iterations topped around 450 to 500 for the AMG solver and around 15002000 for the ICCG solver. Not only that, I also had to reduce the timestep to a very very low value (sometimes even 0.00025) to keep the Courant number from blowing up (stability requirement). After properly creating the mesh (and by that I mean not exceeding an aspect ratio of 1:5 on any cell in the domain and keeping it strictly orthogonal), the multigrid solver took only 100120 iterations despite the new mesh being 4 times as big as what it was before! To sum up crappy discretization is identically equal to crappy performance. 
Update: On the proper mesh, th
Update: On the proper mesh, the number of iterations for the AMG solver has reduced to around 40 now. Only the first 510 iterations topped around 100150.

This is interesting.
By sayin
This is interesting.
By saying 'the new mesh being 4 times as big as what it was before' you mean around 4 million cells? BTW. just because of my curiosity, what kind of hardware/machine are you using? 
Exactly. 4 million cells with
Exactly. 4 million cells with optimal discretization solves faster than 1 million cells with crappy discretization.
Check one of the earlier messages on this forum concerning Superlinear speedup. The machine info is listed there. 
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