Size functions (fixed, curvature, and proximity'' types) allow you to control size of mesh intervals for edges and mesh elements for faces/volumes. Size functions are similar to boundary layers in that they control mesh characteristics in the proximity of the entities to which they are attached.
However, size functions do not control specific mesh patterns or sizes of elements (boundary layers do). They do control maximum mesh-element edge lengths (fixed), angles between mesh-element normals (curvature), or number of mesh elements in gap between two geometric entities (proximity)

  • growth rate must always > 1

TOOLS.SFUNCTION.BGRID_NONLINEAR_ERR_PERCENT<

TOOLS.SFUNCTION.BGRID_NONLINEAR_ERR_PERCENT specifies maximum allowable percentage difference between exact and interpolated size-function values: if the calculated difference > max allowable difference, it will subdivide further until the given condition is satisfied

Note on Undoing

When meshing without running “bgrid” command first, it will auto-run bgrid before meshing – therefore, two operations need to be undone to reverse mesh/size-function operation!

Fixed-type size function

  • start size = mesh-element edge length in the region immediately adjacent to source entity
  • growth rate = increase in mesh-element edge length with each succeeding layer (e.g., 1.2 = 20%)
  • max size = maximum allowable mesh-element edge length for attachment

Meshed size functions’ start size depend on existing mesh on source entity

  • Gambit can blend meshed size functions in areas affected by two or more, but will not by default
  • engage blend through TOOLS.SFUNCTION.MESHED_BLENDING

Curvature-type size function

use for highly curved surfaces (like blades and wings), volumes where tetrahedral elements may not fit

  • source = curved surface (e.g., of wing)
  • angle = maximum allowable angle between outward normals of adjacent elements
  • growth rate = increase in mesh-element edge length with each succeeding layer
  • max size/min size = specify maximum/minimum allowable mesh-element edge length

Proximity-type size function

specify minimum number of mesh-element layers created in “gap” regions <br> gap = internal volume between two faces OR area between opposing boundary edges of a face

  • cells/gap = number of layers of mesh elements in gap define by source faces
  • growth rate = increase in mesh-element edge length with each succeeding layer of elements outside the gap regions
  • max size/min size = specify maximum/minimum allowable mesh-element edge length outside gap regions