Wind-US User's Guide - Keyword Reference, PERIODIC

(Wind-US Documentation Home Page) (Wind-US User's Guide) (GMAN User's Guide) (MADCAP User's Guide) (CFPOST User's Guide) (Wind-US Utilities) (Common File User's Guide) (Wind-US Installation Guide) (Wind-US Developer's Reference) (Guidelines Documents)

(Introduction) (Tutorial) (Geometry and Flow Physics Modeling) (Numerical Modeling) (Boundary Conditions) (Convergence Monitoring) (Files) (Scripts) (Parallel Processing) (Keyword Reference) (Test Options)

PERIODIC - Periodic boundaries

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:

In graphics mode, from the main menu select BOUNDARY COND.
Pick the zone and boundary for one of the two periodic boundaries.
If the boundary condition at the boundary is not UNDEFINED (you may select IDENTIFY POINTS to check), change it to UNDEFINED by doing:
- Select MODIFY BNDY.
- Select CHANGE ALL.
- Select UNDEFINED.
- From the main menu, select BOUNDARY COND.
- Select YES-UPDATE FILE.
Select MODIFY BNDY.
Select COUPLE.
Select SEL OTHER BND.
Pick the zone and boundary for the other periodic boundary. (Note that no default zone is pre-selected here, even for single-zone grids, so you must select both the zone and boundary.)
Select SET COUP MODE.
Under CONNECT MODE, click on the "** NONE **".
Respond to the prompts at the bottom of the screen to set the connection mode, and to specify the translation or rotation data.
Select CONNECT (not COUPLE) to actually connect the two boundaries.

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