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Old   December 10, 2009, 11:45
Default Multigrid Cycle
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Daniele
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Hi, what is the difference between Multigrid V-cycle, W-cycle and F-cycle? I'm studying 2D subsonic (Mach about 1,15 - 2,0) flow over an airfoil, and comparing different turbulence model.
I've saw that with F-Cycle the convergence is more smooth than with the other cycle type, it's normal?
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Old   December 11, 2009, 05:24
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Ioan
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Hi,

Philosophy:

The solution of the linear system is not calculated on the original grid (see below 1), but will be calculated on a coarse grid (in order to reduce its dimension...) and then the solution will pe prolonged on the original mesh.

Ex: V cycle:
Actual grid - delx - 1: o o or o o ...
Coarse grid - 2*delx - 2: o o o
Coarse grid - 4*delx - 3: o
...

Ex: W cycle:
Actual grid - delx - 1: o o o or o o ...
Coarse grid - 2*delx - 2: o o o o o
Coarse grid - 4*delx - 3: o o
....

F cycle means flexible cycle and the code will choose for you the best strategy.

The convergence depends on the structure of the linear system beeing solved. In your case it seems that the F cycle "behaves" better for your special setup.
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