The Boundary Conditions tab allows you to specify how each bounding connector of a domain will be treated when using the T-Rex anisotropic meshing tool. The list operates nearly identically to the Set Boundary Conditions command for CAE use. It displays information on all the boundary conditions that have been set (including for blocks) regardless of your current domain selection.
This is the basic workflow:
Tip: The boundary conditions table has quite a few columns, but all of the columns to the right of the Value column are optional and can be hidden to declutter your view. Simply right-click in the header row of the table to bring up a menu to hide/show the optional columns.
When setting T-Rex boundary conditions, the currently selected connectors are highlighted in white (see figure below). Note that when there is either a connection between two domains or a baffle connector, arrows normal to the boundary are rendered to indicate which side of the connection or the baffle you are currently selecting.
There are seven types of boundary conditions available for the T-Rex algorithm:
Angle: Sets bounding connectors to have anisotropic cells (quads and/or triangles) grown off of them. Use the Value column to define the 2D T-Rex turning angle (expressed in degrees) used to compute a variable initial height for the anisotropic cells along the bounding connectors.
This computation consists of walking along the bounding connectors assigned to this T-Rex boundary condition and sampling the underlying database surface in the transverse direction. For each grid point on the connectors (Point A), the algorithm will find the closest point on the underlying database surface (Point B) for which the angle between the normals to the underlying database surface at Point A and Point B is smaller than or equal to the specified turning angle. The distance between Point A and Point B is the calculated initial height at that particular grid point.
The final result is a smoothed distribution of T-Rex initial height values at each grid point along the connectors assigned to this T-Rex boundary condition. In the case when this T-Rex boundary condition is applied to both sides of a shared connector, the minimum spacing will be used in both domains.
Tip: The Angle T-Rex boundary condition calculates a distribution of T-Rex initial heights along the connectors bounding a given domain based on the curvature of the underlying database surface. This functionality therefore requires the domain in question to be constrained to such database surface.
Aspect Ratio: Sets bounding connectors to have anisotropic cells (quads and/or triangles) grown off of them. Use the Value column to define the aspect ratio used to compute a variable initial height of the anisotropic cells along the bounding connectors.
This computation consists of walking along the bounding connectors assigned to this T-Rex boundary condition and calculating an initial height for each line segment in the connector (i.e. the segment between two consecutive grid points) based on the length of the line segment and the specified aspect ratio. The final result is a smoothed distribution of T-Rex initial height values at each grid point along the connectors assigned to this T-Rex boundary condition.
Tip: When applying T-Rex boundary conditions, you can always leave connectors as Unspecified when you want to use type Off since Unspecified defaults to the Off boundary condition type.
The Adapt column specifies that connectors assigned to the boundary condition have their point clustering adapted (points will be added or removed) in order to meet the target cell sizes specified by any selected size field influencers on the Size Field tab. The Adapt column is set to Off by default and can be toggled On by double clicking in the field. Adaptation is not available for the Unspecified boundary condition.
Note: Even though T-Rex layers are not directly influenced by the size field, the Adapt option can still be applied to any T-Rex condition that grows anisotropic cells (Wall, Angle, Aspect Ratio, Max. Aspect Ratio, and Adjacent Grid). In this case, the connectors will be adapted prior to marching T-Rex layers, thus picking up the influence from the size field.
The remaining columns (Growth Rate, Constant Layers, Min. Edge Length, and Min. Radius of Curvature) are only available for T-Rex boundary conditions that grow anisotropic cells (i.e. Wall, Angle, Aspect Ratio, Max. Aspect Ratio, and Adjacent Grid) and function similarly to the Automatic Surface Mesh Stretching Filter parameters of the same names.
The Growth Rate and Constant Layers columns provide more fine-tuned control of the growth schedule for individual T-Rex boundary conditions. By default, T-Rex uses the growth rate specified on the T-Rex tab. The Constant Layers column allows you to specify an integer number of constant growth layers before the Growth Rate is applied and has a default value of 0. Double click in the corresponding field to specify a different value for the assigned connectors.
The Min. Edge Length and Min. Radius of Curvature columns allow you to specify a minimum edge length and radius of curvature, respectively, to be used with adaptation for the assigned connectors. These are intended to limit excessive over-refinement of the connectors due to inconsistencies in the geometry definition.