B.3.7 Faces

Index:	13
Scheme symbol:	xf-face
C macro:	XF_FACE
Status:	required

The format for face sections is as follows:

      (13 (zone-id first-index last-index bc-type face-type))

where

zone-id	=	zone ID of the face section
first-index	=	index of the first face in the list
last-index	=	index of the last face in the list
bc-type	=	ID of the boundary condition represented by the face section
face-type	=	ID of the type(s) of face(s) in the section

The current valid boundary condition types are defined in the following table:

bc-type	description
2	interior
3	wall
4	pressure-inlet, inlet-vent, intake-fan
5	pressure-outlet, exhaust-fan, outlet-vent
7	symmetry
8	periodic-shadow
9	pressure-far-field
10	velocity-inlet
12	periodic
14	fan, porous-jump, radiator
20	mass-flow-inlet
24	interface
31	parent (hanging node)
36	outflow
37	axis

The faces resulting from the intersection of non-conformal grids are placed in a separate face zone, where a factor of 1000 is added to the bc-type (e.g., 1003 is a wall zone).

The current valid face types are defined in the following table:

face-type	description	nodes/face
0	mixed
2	linear	2
3	triangular	3
4	quadrilateral	4
5	polygonal	NN

where NN will vary, depending on the specific polygonal face.

A zone-id of zero indicates a declaration section, which provides a count of the total number of faces in the file. Such a section omits the bc-type and is not followed by a body with further information.

A non-zero zone-id indicates a regular face section, and will be followed by a body that contains information about the grid connectivity. Each line of the body will describe one face and will have the following format:

      n0 n1 n2 c0 c1

where,

n*	=	defining nodes (vertices) of the face
c*	=	adjacent cells

This is the format for a 3D grid with a triangular face format. The actual number of nodes depends on the face-type. The order of the cell indices is important, and is determined by the right-hand rule: if you curl the fingers of your right hand in the order of the nodes, your thumb will point toward c1.

For 2D grids, n2 is omitted. c1 is determined by the cross product of two vectors, $\hat{r}$ and $\hat{k}$. The $\hat{r}$ vector extends from n0 to n1, whereas the $\hat{k}$ vector has its origin at n0 and points out of the grid plane toward the viewer. If you extend your right hand along $\hat{r}$ and curl your fingers in the direction of the angle between $\hat{r}$ and $\hat{k}$, your thumb will point along $\hat{r} \times \hat{k}$ toward c1.

If the face zone is of mixed type ( face-type = 0), each line of the section body will begin with a reference to the number of nodes that make up that particular face, and has the following format:

      x n0 n1 ... nf c0 c1

where,

x	=	the number of nodes (vertices) of the face
nf	=	the final node of the face

All cells, faces, and nodes have positive indices. If a face has a cell only on one side, then either c0 or c1 is zero. For files containing only a surface mesh, both these values are zero.

For information on face-node connectivity for various cell types in ANSYS FLUENT, refer to Section  6.1.2.