AIM Inputs

The following list outlines the AFLR4 meshing options along with their default value available through the AIM interface.

Please consult the AFLR4 documentation for default values not present here.

• Proj_Name = "aflr4_CAPS"
  Output name prefix for meshes to be written in formats specified by Mesh_Format. These meshes are not linked to any analysis, but may be useful exploring meshing parameters.

• Mesh_Format = NULL
  Optional list of string mesh formats to generate meshes not linked to analysis.
  Available format names include: "exodus", "fast", "libMeshb", "stl", "bstl", "su2", "tecplot", "ugrid", "vtk", "bvtk", "vtu", "wavefront".
  where the "b" prefix indicates binary version.

• Mesh_Quiet_Flag = False
  Complete suppression of mesh generator (not including errors)
• Mesh_Gen_Input_String = NULL
  Meshing program command line string (as if called in bash mode). Use this to specify more
  complicated options/use features of the mesher not currently exposed through other AIM input
  variables. Note that this is the exact string that will be provided to the volume mesher; no
  modifications will be made. If left NULL an input string will be created based on default values
  of the relevant AIM input variables.
• ff_cdfr
  Farfield growth rate for field point spacing.
  The farfield spacing is set to a uniform value dependent upon the maximum size
  of the domain, maximum size of inner bodies, max and min body spacing, and
  farfield growth rate. ;
  ff_spacing = (ff_cdfr-1)*L+(min_spacing+max_spacing)/2 ;
  where L is the approximate distance between inner bodies and farfield.
  
• min_ncell
  Minimum number of cells between two components/bodies.
  Proximity of components/bodies
  to each other is estimated and surface
  spacing is locally reduced if needed. Local
  surface spacing is selectively reduced when
  components/bodies are close and their
  existing local surface spacing would generate
  less than the minimum number of cells
  specified by min_ncell. Proximity checking is
  automatically disabled if min_ncell=1 or if
  there is only one component/body defined.
• mer_all <Boolean>
  Global edge mesh spacing scale factor flag.
  Edge mesh spacing can be scaled on all surfaces based on discontinuity level
  between adjacent surfaces on both sides of the edge. For each surface the level
  of discontinuity (as defined by angerw1 and angerw2) determines the edge
  spacing scale factor for potentially reducing the edge spacing. See erw_ids and
  erw_list. This option is equivalent to setting erw_ids equal to the list of all
  surface IDS and the edge mesh spacing scale factor weight in erw_list equal to
  one. Note that no modification is done to edges that belong to surfaces with a
  grid BC of farfield (ff_ids) or BL intersecting (int_ids).
• no_prox
  Disable proximity check flag.
  If no_prox=False then proximity of components/bodies to each other is estimated
  and surface spacing is locally reduced if needed.
  If no_prox=True or if there is only one component/body defined then proximity
  checking is disabled.
  
• BL_thickness
  Boundary layer thickness for proximity checking.
  Proximity of components/bodies to each other is estimated and surface spacing
  is locally reduced if needed. Note that if the Reynolds Number, Re_l, is set
  then the BL_thickness value is set to an estimate for turbulent flow. If the
  set or calculated value of BL_thickness>0 then the boundary layer thickness is
  included in the calculation for the required surface spacing during proximity
  checking.
• Re_l
  Reynolds Number for estimating BL thickness.
  The Reynolds Number based on reference length, Re_l, (if set) along with
  reference length, ref_len, are used to estimate the BL thickness, BL_thickness,
  for turbulent flow. If Re_l>0 then this estimated value is used to set
  BL_thickness.
• curv_angle
  Curvature spacing angle in degrees.
  
  For curvature refinement the spacing is derived from the curvature spacing angle and the curvature.
  Curvature = 1 / Curvature_Radius
  Spacing = [2*sin(curv_angle/2)] / Curvature
  For example, if the surface is circular and the curvature angle is 10 degrees, this will provide mesh points spaced every 10 degrees. If the Curvature is 0, then the surface is flat and the spacing is set to the maximum spacing (max_spacing = max_scale*ref_len). Note that the curvature based spacing may be overridden by constraints imposed by surface boundary edge lengths or adjacent surfaces.
  The curvature spacing angle curv_angle replaces the previous curvature factor curv_factor parameter.
  curv_factor = 2*sin(curv_angle/2)
  The default value for curv_angle produces a value for the previous curv_factor that is approximately the same as its default value.
• erw_all
  Global edge mesh spacing refinement weight.
  
  Edge mesh spacing can be scaled on all surfaces (if mer_all=1) based on
  discontinuity level between adjacent surfaces on both sides of the edge.
  For each surface the level of discontinuity (as defined by angerw1 and angerw2)
  determines the edge spacing scale factor for potentially reducing the edge
  spacing. The edge mesh spacing scale factor weight is then used as an
  interpolation weight between the unmodified spacing and the modified spacing.
  A value of one applies the maximum modification and a value of zero applies no
  change in edge spacing. If the global edge mesh spacing scale factor flag,
  mer_all, is set to 1 then that is equivalent to setting AFLR_Edge_Scale_Factor_Weight
  on all FACEs to the value erw_all. Note that no modification is
  done to edges that belong to surfaces with a grid BC of farfield (FARFIELD_UG3_GBC) or BL
  intersecting. Also, note that the global weight, erw_all, is not
  applicable if mer_all=0.
• max_scale
  Relative maximum spacing.
  
  The relative maximum spacing (max_scale) is used along with the reference length (ref_len) to set the maximum spacing used for flat surfaces, except farfield or symmetry plane surfaces, if any.
  max_spacing = max_scale * ref_len
• ideal_min_scale
  Relative ideal minimum spacing.
  The relative ideal minimum spacing (ideal_min_scale) is used along with the
  reference length (ref_len) to categorize individual surfaces, except farfield
  or symmetry plane surfaces, if any.
  ideal_min_spacing = ideal_min_scale * ref_len
• curv_min_scale
  Relative curvature minimum spacing limit.
  The relative minimum spacing limit (curv_min_scale) can be used along with the
  reference length (ref_len) to limit the minimum spacing used for curved
  surfaces, except farfield or symmetry plane surfaces, if any. Note that using
  the default value of zero for curv_min_scale will allow the surface curvature to
  determine the minimum spacing based on the curv_angle and geometry evaluation
  tolerance (from CAD geometry data). Setting a non-zero value of min_scale (e.g.
  min_scale=0.005) may be useful for successfully meshing a case with a poorly
  defined geometry. It is not needed for well defined geometry.
  curv_min_spacing = curv_min_scale * ref_len
• abs_min_scale
  Relative proximity minimum spacing.
  
  The relative proximity minimum spacing (prox_min_scale) is used along with the reference length (ref_len) to limit the minimum spacing produced by proximity checking between component/body surfaces (see auto_mode).
  prox_min_spacing = prox_min_scale * ref_len
• Mesh_Length_Factor = 1
  Global scaling factor to increase or decrease mesh resolution.
  

ref_len:
Reference length for components/bodies in grid units. Reference length should
be set to a physically relevant characteristic length for the configuration
such as wing chord length or pipe diameter. If ref_len = 0 then it will be set
to the bounding box for the largest component/body of interest.
The parameters ref_len, max_scale, min_scale and abs_min_scale are all used to
set spacing values on all component/body surfaces (those that are not on the
farfield or symmetry plane-if any).

max_spacing = max_scale * ref_len
min_spacing = min_scale * ref_len
abs_min_spacing = abs_min_scale * ref_len

• Mesh_Sizing = NULL
  See Mesh Sizing for additional details.
• Multiple_Mesh = "SingleDomain"
  If "SingleDomain": Generate a single surface mesh file is assuming multiple bodies define a single computational domain (i.e. CFD)
  
  If "MultiFile": Generate a surface mesh file for each body.
  
  If "MultiDomain": Generate a single mesh file containing multiple surface meshes for each body.
  
• EGADS_Quad = False
  If true, apply EGADS quadding to the AFLR4 triangulation.
• AFLR4_Quad = False
  If true, apply -quad flag for AFLR4 quadding.
• skin = False
  If true, apply -skin flag to automatically set the grid BCs for structural cases.