Periodic boundaries are treated as normal coupled boundaries, with the connection data stored in the grid (.cgd) file. Either MADCAP or GMAN may be used to set up periodic boundary conditions.
In GMAN, the CONNECT MODE option is used to specify how to move one boundary surface to overlay it on the corresponding periodic boundary surface. There are two connection modes - translation and rotation. For translation, the user defines the Δx, Δy, and Δz movement for the surface. For rotation the user sets the center of rotation and the angles. GMAN then moves the current boundary surface using the specified method, and attempts to couple the two surfaces together as if they were coexistent boundaries. If successful, it saves the data as normal coupling data for Wind-US. Thus the boundaries look connected even though they are physically separated. The periodic boundary surfaces do not have to be in the same zone, nor do they have to be point matched. They only have to line up physically once the movement has been performed.
Specifically, to set a periodic boundary condition in GMAN:
For structured grids, another procedure is available for setting up a periodic boundary condition within a single zone, and may be useful for cases with higher-order differencing schemes. See the description of TEST 72 and TEST 73 for details.
Last updated 1 Apr 2016