The secondary flow path objects listed under Mesh Data provide the following functions:
The object editor for a secondary flow path object provides controls that affect the mesh within the bulk of the secondary passage.
The object editor for a given boundary of a secondary flow path object provides similar settings that affect the mesh near the boundary. These settings enable you to override, for the applicable boundary, the default settings that are established for the secondary flow path (parent object).
Triangle Refinement Factor
As this value increases, the element size in the mesh interior decreases.
Default Boundary Edge Refinement Factor
As this value increases, the node spacing along the boundary decreases.
Inflation Options
Default Number of Boundary Layers
The number of rows of hexahedral elements in the inflation layer.
Default Inflation Growth Ratio
Height ratio between a row of mesh elements in the inflation layer and the adjacent row closer to the boundary.
Advanced Options
Default Last Layer Height Ratio
This is the length scale ratio between the boundary layer mesh elements and the interior mesh elements where the boundary layer elements meet the interior elements.
Default Maximum Feature Angle and Default Curvature Angle
Decreasing the Maximum Feature Angle reduces the "detection" of boundary curve details.
Increasing the Curvature Angle reduces the number of elements along a curved section of the boundary.
Note that the Maximum Feature Angle and Curvature Angle values must sum to a value greater than 180 degrees.
Default Cells Per Gap (Proximity Refinement)
This parameter controls the mesh proximity. Increasing this value increases boundary and interior mesh refinement in narrow gaps.
3D Options (available only for the secondary flow path object, not a boundary object)
A secondary flow path is typically modeled as a sector of the full 360° geometry. The appropriate pitch (angular extent about the rotation axis) of the sector, and number of elements across the pitch, depend on details of the intended CFD simulation:
If you intend to connect the main passage to the secondary flow path using a mixing plane interface (to model swirling flow with no circumferential variation) then the secondary flow path can be modeled using a thin, almost 2D, mesh that has a minimum of 2 layers of mesh elements across the pitch.
If you want to model circumferential flow variations in the secondary flow path (for example using a
Frozen RotororTransient Rotor-Statorframe change model in CFX) then the secondary flow path should have an appropriate pitch.
The settings under 3D Options are:
Number of Extrusions
Specify the number of rows of elements to generate (minimum 2) in the circumferential direction.
Theta Extrusion Angle
Specify the sector angle (pitch) for the secondary flow path mesh.
Theta Extrusion Base
Specify the starting value of Theta for the mesh extrusion.
Inflation Zone
This setting controls whether or not inflation is applied at the specified boundary. A value of
Defaultapplies inflation if the boundary is a wall; it applies no inflation if the boundary is an interface.First Layer Height
A read-only display of the average height of the row of mesh elements next to the boundary.
Note: There is no setting to directly control the first element height in an inflation region. However, you can see the average height in the object editor for a boundary. To increase/decrease the height, decrease/increase the number of boundary layers. Other mesh factors affect the height, including the Global Size Factor (see Method).
Use Override Boundary Settings (available only for a boundary object, not the secondary flow path object)
Select this option to override defaults set for the secondary flow path object:
Freeze Edges
Try changing this option if there is a mesh quality problem at a transition between a boundary with an inflation layer and a boundary without an inflation layer.