|Type of mesh
The CHAD interface writes an input file for the CRADA code CHAD. This
input file contains the following sections:
NELEM, NNODES, NPARENTS, NCONNS, NCHEMS
NELEM: number of elements
NNODES: number of nodes
NPARENTS and NCONNS are set to zero.
NCHEMS: number of chemical species, set to zero.
Nodal X-coordinates (NNODES values).
Nodal Y-coordinates (NNODES values).
Nodal Z-coordinates (NNODES values).
NODESV: List of nodes associated with each element (8xNELEM values). For
degenerated elements, the nodes are repeated to insure that 8 values are
input for each element.
ICOLORN: Node color (NNODES values). Here all ICOLORN are set to one.
MATNON: Node material number (NNODES values).
REGNON: Node region number (NNODES values).
NODETYPE: User defined node type (NNODES values).
CONTAB: Boundary constraint table (6xNNODES values).
EPS: User defined turbulent-energy dissipation (NNODES values).
P: User defined pressure (NNODES values).
T: User defined temperature (NNODES values).
TKE: User defined kinetic energy (NNODES values).
U: X-component of the velocity (NNODES values).
V: Y-component of the velocity (NNODES values).
W: Z-component of the velocity (NNODES values).
ICOLORE: Element color (NELEM values). Here all ICOLORE are set to one.
MATNOE: Element material number (NELEM values).
REGNOE: Element region number (NELEM values).
Creating the CHAD input file
The translator writes the CHAD input file using an unstructured mesh
file and a boundary condition file. To create the CHAD file, select the
translator "CHAD" under the "Output" menu. After
clicking "Write input" you can specify the following options for the CHAD interface:
- select an unstructured mesh
- give the name of the boundary condition file
- give the name of the CHAD input file (default is chad)
- Option to write the data array MATNOE in the CHAD file
- Option to write the boundary file
- Option to specify a scaling factor for each coordinate axis
The interface generates the CHAD input file in the project directory.
Defining boundary conditions and properties for CHAD
Under the "Output" menu, click on the "Boundary Conditions" icon.
The "Family boundary conditions" window opens, allowing to select
families and define their boundary conditions and properties.
Please refer to the General
section for more details.
- Node type: select "Node Type" in the boundary condition menu and specify the node type
- Material number (MATNO): select "Material" in the boundary condition menu and give the material number
- Region number (REGNO): select "Region number" in the obundary condition menu and enter the region number
One can either specify a "user defined nodetype" or a pre-defined nodetype.
A user defined nodetype can be any integer greater than 10 and different
from the pre-defined nodetypes. The pre-defined nodetypes are:
0: regular interior nodes (default)
11: turbulent symmetric boundary (nodetype reset to 0 in CHAD input file)
21: free slip boundary condition
22: symmetry boundary condition
31: no-slip boundary nodes
41: inflow boundary
42: free slip inflow boundary (nodetype reset to 41 in CHAD input file)
43: no-slip inflow boundary (nodetype reset to 41 in CHAD input file)
51: outflow boundary
52: free slip outflow boundary (nodetype reset to 51 in CHAD input file)
53: no-slip outflow boundary (nodetype reset to 51 in CHAD input file)
61: imposed velocity nodes (velocity source)
71: imposed temperature or specified temperature bound. cond. nodes
91: free slip moving boundary
92: no-slip moving boundary (nodetype reset to 91 in CHAD input file)
3002: free slip interface (nodetype reset to 3001 in CHAD input file)
3003: no-slip interface (nodetype reset to 3001 in CHAD input file)
At intersection between areas of different nodetypes, the following precedence
block_type < face_type < edge_type
nodetypes defined on vertices overwrite nodetypes defined on edges, which
overwrite nodetypes defined on surfaces, which overwrite nodetypes defined
on volume families.
internal_face_type < external_face_type
nodetypes defined on external walls have priority over those defined on
When a node receive different types from similar topological entities,
e.g. a node at the intersection of 2 edges having different nodetypes,
the following precedence rule is applied:
Those nodes at the interface of different MATERIALS have a MATNO of
0, and those nodes at the interface of different REGIONS have a REGNO of
Additionally, any node at the interface between two materials is assigned
a NODETYPE of 3001, a type which supercedes all others.
Any 2 digits nodetype can be preceeded by a 2digits boolean mask.
For example, a free slip wall could be assigned nodetype 7121.
The first 2 digits are used to assess the priorities and the last 2
digits represent the nodetypes. The priorities are set as follow:
... < 22 < 21 < 3321 < -7121 < 31 < 5231 < 41
This allows to define a node with more than one attribute.
After selecting "Properties" in the boundary condition menu for CHAD, enter the following values:
- the turbulent-energy dissipation
- the X-component of the velocity
- the Y-component of the velocity
- the Z-component of the velocity
- the pressure
- the temperature (default is 300)
- the turbulent kinetic energy
- the density
All default values are zero except for the temperature. Properties defined
on vertices overwrite properties defined on edges, which overwrite properties
defined on surfaces, which overwrite properties defined on domains.
In the computation of the array CONTAB, the translator must compute
the unit vectors of each node. These are computed differently for nodes
located on edges and nodes located on walls. However, not necessarily all
ANSYS-ICEM edges are considered "edges" in term of CHAD. Therefore the user needs
to select which edges need to be treated like CHAD edges. This is
done by simply selecting the "Edge flag" option in the boundary condition menu.
All interior nodes get by default a type zero and their CONTAB
array is (1,0,0,1,0,1). To specify an interior wall, the user must assign
a free slip (type 21) or a no-slip boundary condition to the surfaces composing
the interior wall. Nodes on edges at the intersection between interior
and exterior walls are treated like exterior wall nodes.
The material numbers (MATNON and MATNOE) are automatically set
by the interface. A distinct material is defined for each 3D-family.
The regions are user-defined by tagging the different families
with a region name. All families having the same
region name are grouped together. All 3D-families which do not
have a region name, are automatically grouped in a distinct region. Therefore
if no region name is given for the whole model, all elements are included
in region #1. Any region name is allowed, up to 5 characters. The regions
are written in arrays REGNOE and REGNON in the CHAD file.
To define a region name, select "Region Name" in the boundary condition menu
and enter the region name
The array CONTAB is reset to zero for all blocks and faces tagged with
the keyword SOLID. To tag a family as solid, select "Solid Tag" in
the boundary condition menu.
This interface in only written for 3D models.