7.13.1.21. Periodic BCs

This section is referenced in the following other sections

Simulation Setup: Boundary Conditions

7.13.1.21.1. Periodic

Scope

Aria Region

Summary

The periodic command block is used to define periodic, or cyclic, boundary conditions.

Description

For standard periodic boundary conditions, the line commands SOURCE, COPY, SEARCH TOLERANCE should appear, while the line commands THETA, POINT ON AXIS, and REFERENCE AXIS must not appear.

Cyclic boundary conditions, the line commands SOURCE, COPY, SEARCH TOLERANCE, THETA, POINT ON AXIS, and REFERENCE AXIS must appear.

Two self-similar side sets for the boundary condition are specified by the SOURCE and COPY command lines. It must be possible to replicate the coordinates for the nodes in one set by a simple translation of the corresponding nodes in the other set.

A geometric check is made to determine if the side sets are self similar. The geometric check is set to a certain tolerance. This tolerance must be set to a small positive number (e.g. $10^{-4}$ ) by using the command line SEARCH TOLERANCE. After translation each node in the set of copy nodes lies within a radius defined by the search tolerance from a node in the set of master nodes. Additionally, upon transformation, copy nodes must lie in the interpolation space of at least one facet in the master surface. When these two conditions are satisfied the two sets are considered self-similar.

begin Periodic Name

   Copy {=} name

   Master {=} Master

   Point On Axis {=} Point

   Reference Axis {=} Axis

   Search Tolerance {=} SearchTolerance

   Slave {=} Slave

   Source {=} name

   Theta {=} Theta

end Periodic Name

Line Commands

Copy

Syntax: Copy {=} name
Summary: Defines copy surface for this interaction. When used in Aria this must be a sideset.

Parameter	Value	Default
{=}	{= \| are \| is}	–
name	string	–

Master

Syntax: Master {=} Master
Summary: Defines master surface for this interaction. When used in Aria this must always be a sideset.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Master	string	–

Point On Axis

Syntax: Point On Axis {=} Point
Summary: This line command defines a point that lies on the reference axis.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Point	string	–

Reference Axis

Syntax: Reference Axis {=} Axis
Summary: This line command defines the reference wedge axis for the periodic BC about which a source surface is rotated to transform it into the copy surface.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Axis	string	–

Search Tolerance

Syntax: Search Tolerance {=} SearchTolerance
Summary: This line command defines the search tolerance used to determine if two node sets are self similar.

Parameter	Value	Default
{=}	{= \| are \| is}	–
SearchTolerance	real	–

Slave

Syntax: Slave {=} Slave
Summary: Defines slave surface for this interaction. When used in Aria, this must be a sideset.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Slave	string	–

Source

Syntax: Source {=} name
Summary: Defines source surface for this interaction. When used in Aria, this must always be a sideset.

Parameter	Value	Default
{=}	{= \| are \| is}	–
name	string	–

Theta

Syntax: Theta {=} Theta
Summary: This line command defines the angle, in degrees, for a periodic boundary condition. A positive angle is defined by sweeping the source surface through the domain to the copy surface about the reference axis.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Theta	real	–

7.13.1.21.2. Define Direction

Syntax: Define Direction DirectName With Vector Components1 Components2 Components3
Summary: Defines a named spatial direction in terms of vector components.

Parameter	Value	Default
DirectName	string	–
Components	real1 real2 real3	–

7.13.1.21.3. Define Point

Syntax: Define Point PointName With Coordinates Coordinates1 Coordinates2 Coordinates3
Summary: Defines a named point in space in terms of its coordinates.

Parameter	Value	Default
PointName	string	–
Coordinates	real1 real2 real3	–