The Neutral Map File
The neutral map file provides a formatted summary of information relating to
the size and composition of the mesh,
the topological features of the mesh and
assigned flow field boundary conditions
which is typically required of any multi-block flow solver.
The formatting of this file is "neutral" in that it is not specific to any particular
flow solver, thus a reformatting of the data will be required before use.
To serve as an example, a neutral map file for a simply-connected four block mesh is listed below.
The specifics of the configuration are not important here as the goal of this description is
to give an idea of the typical content and organization of such a file.
The file consists of two sections; the first defines the size (in blocks) of the mesh as well as
the size of each block within the mesh,
and the second section defines the topological features of the mesh which may involve
point continuous block interfaces,
singularities and/or
patched interfaces.
Also included in the summary are any flow field boundary conditions which have been placed by the
user.
# ===== Neutral Map File generated by the V2k software of NASA Langley's GEOLAB =====
# ===================================================================================
# Block# IDIM JDIM KDIM
# -----------------------------------------------------------------------------------
4
1 47 26 33
2 19 26 33
3 19 24 33
4 47 24 33
# ===================================================================================
# Type B1 F1 S1 E1 S2 E2 B2 F2 S1 E1 S2 E2 Swap
# -----------------------------------------------------------------------------------
WALL 1 1 1 47 1 26
WALL 1 2 1 47 1 26
ONE_TO_ONE 1 3 1 26 1 33 2 4 1 26 1 33 FALSE
outflow 1 4 1 26 1 33
ONE_TO_ONE 1 5 1 33 1 47 4 6 1 33 1 47 FALSE
WALL 1 6 1 33 1 47
WALL 2 1 1 19 1 26
WALL 2 2 1 19 1 26
Inflow 2 3 1 26 1 33
ONE_TO_ONE 2 5 1 33 1 19 3 6 1 33 1 19 FALSE
WALL 2 6 1 33 1 19
WALL 3 1 1 19 1 24
WALL 3 2 1 19 1 24
Inflow 3 3 1 24 1 33
ONE_TO_ONE 3 4 1 24 1 33 4 3 1 24 1 33 FALSE
WALL 3 5 1 33 1 19
WALL 4 1 1 47 1 24
WALL 4 2 1 47 1 24
outflow 4 4 1 24 1 33
WALL 4 5 1 33 1 47
Associated with each topological entry and boundary condition is a description
as to its location within the mesh.
Each of the entries in the second section of this file are defined in detail within the table below.
Topological Feature Description
| Entry |
Definition |
| Type |
The type of featured (topological or boundary condition) to be defined and positioned within the mesh.
Valid entries for Type are summarized in the table below. |
| B1 | The number of the first block associated with the Type. |
| F1 | The face number for the specified block.
Valid entries for Face are summarized in the table below. |
| S1 | The starting index in the primary coordinate direction for the face. |
| E1 | The ending index in the primary coordinate direction for the face. |
| S2 | The starting index in the secondary coordinate direction for the face. |
| E2 | The ending index in the secondary coordinate direction for the face. |
| B2 | The second block number associated with the Type. |
| F2 | The face number for the specified block. |
| Swap | Orientation flag (specified only for Type = ONE_TO_ONE.
This flag is TRUE if the primary directions of the two identified faces are aligned (though
perhaps in opposite directions) and FALSE otherwise. |
The valid entries under the Type heading are as given in the table below.
Summary of Valid Interface Types
| Type Name |
Definition |
| Collapsed | Face collapsed to a single point (V2K will not
detect this kind of interface automatically; it must be user defined via direct editing of the neutral map file). |
| ONE_TO_ONE | A point-to-point continuous interface between two blocks the valid index range for which is described as listed above. Such an interface may comprise any portion of the block face.
This type also requires the specification of a secondary block, face and indices describing the complete connectivity.
V2K provides facilities to detect this type of interface automatically. |
| Patched | A block interface for which point-to-point continuity does not exist
though flux transport ocurrs across the identified face. V2K provides facilities
to identify this type
of interface which is described similarly to the ONE_TO_ONE interface type. The exception is that the
full index range of both counterparts are listed and it is left to the flow solver to define the
appropriate index range and interpolation parameters. |
| POLE_DIR1 | Describes a singularity within a block for which the collapsed edge
corresponds to the primary direction of the face.V2K provides facilities to detect this type of interface automatically. |
| POLE_DIR2 | Describes a singularity within a block for which the collapsed edge
corresponds to the secondary direction of the face.V2K provides facilities to detect this type of interface automatically. |
| Symmetry-X | A flow field boundary condition which is to provide for symmetry
in the x-direction. |
| Symmetry-Y | A flow field boundary condition which is to provide for symmetry
in the y-direction. |
| Symmetry-Z | A flow field boundary condition which is to provide for symmetry
in the z-direction. |
| UNPROCESSED | A block boundary or portion thereof for which no Type
assignment has been made. An initial neutral map file will be composed only of this type and a completed
(and valid) neutral map file will have none of this type. |
| WALL | A solid wall boundary condition whose actual interpretation (slip
or no-slip) will depend upon the type of flow solver to be employed. |
Note that additional boundary conditions may be user defined.
Lastly, the face number specification
identifies a particular face within a block whose position is dependent upon the local coordinate
system employed within that block. This relationship is summarized in the table below.
Block Face Identification
| Face Number |
constant index |
primary coordinate |
secondary coordinate |
| 1 | kmin |
i | j |
| 2 | kmax |
i | j |
| 3 | imin |
j | k |
| 4 | imax |
j | k |
| 5 | jmin |
k | i |
| 6 | jmax |
k | i |
Other than for the meaning attached to each of the flow field boundary condition types,
the user need not be overly
concerned with the mechanics of constructing the neutral map file as the software does this essentially
automatically. In the event that the user must make alterations or additions to this file via a text
editor, careful attention to the definitions provided is in order.
|
