CHAD Interface

Solver Nastran
Type of mesh unstructured mesh
Dimension 3D



The CHAD interface writes an input file for the CRADA code CHAD. This input file contains the following sections:

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: 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 Remarks section for more details.

Boundary conditions:

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: At intersection between areas of different nodetypes, the following precedence rules apply:       block_type < face_type < edge_type       internal_face_type < external_face_type Boolean Mask:

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:

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.

 Edge tagging:

 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.

Interior walls:

 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

"Solid" condition

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.