Each triangular element will have 3 nodes specified, a rectangular element would have 4 nodes specified, a tetrahedral element would have 4 nodes specified, and so on. Following the identifier is a list of the node indices that make up the element. In our square mesh, all elements are triangles, and thus the identifier (first integer) on all lines is 5. The identifiers follow the VTK format: Element Type SU2 supports line, triangle, quadrilateral, tetrahedral, pyramid, prism, and hexahedral elements. The first integer on each line is a unique identifier for the type of element that is described. This global element index is implied by the ordering and does not need to be explicitly specified by the file, although some legacy meshes may still contain an explicit index at the end of the line that can be ignored.Įach following line describes the connectivity of a single element. For the square mesh above, this corresponds to the 8 triangular interior elements that are assigned a global element index of 0 through 7 in the order they appear in the file. This value is given first, as it is used to set up a loop over all of the elements which must immediately follow this line. First, SU2 will search for the string NELEM= and then store the number of interior elements. Unlike for structured meshes where a logical, ordered indexing can be assumed for neighboring nodes and their corresponding cells (quadrilaterals in 2D and hexahedral elements in 3D), for an unstructured mesh, a list of nodes that make up each element, or the connectivity as it is often called, must be provided. SU2 is based on unstructured mesh technology, and thus supports several element types for both 2D and 3D elements. The next part of the file describes the interior element connectivity, which begins with the NELEM= keyword: The location of each node in the list can be confirmed in space by adding 1 to the implied global index from the ordering and comparing with the figure above. Note that the global index values for the nodes and elements stored within SU2 are zero-based, as opposed to starting from 1 as Tecplot does. This global element index is implied by the ordering and does not need to be explicitly specified by the file, although some legacy meshes may still contain an explicit index at the end of the line that can be ignored.įor a 2D mesh, only x and y coordinates are required, but a 3D mesh would give x, y, and z coordinates. The grid points are assigned a global element index of 0 through 8 in the order they appear in the file. Each line gives the coordinates for a single grid vertex. Immediately after the node number specification comes the list of node coordinates in cartesian space. In this case, there are 9 nodes in the 3x3 square above. For the 2D square mesh, the dimension is defined as follows: As a note, for 2D simulations, it is recommended that a truly 2D mesh is used (no z-coordinates) rather than a quasi-2D mesh (one or more cells deep in the third dimension with symmetry boundary conditions). su2 mesh declares the dimensionality of the problem. The node and element numbering for SU2 start at 0. Square Mesh Example: Note that the figure uses Tecplot node and element number (1-based). SpecificationĬonsider the following simple, 2D mesh for a square domain consisting of 8 triangular elements. Lastly, the boundaries of the mesh, or markers, are given names, or tags, and their connectivity is specified in a similar manner as the interior nodes. The connectivity description provides information about the types of elements (triangle, rectangle, tetrahedron, hexahedral, etc.) that make up the volumes in the mesh and also which nodes make up each of those elements. As an unstructured code, SU2 requires information about both the node locations as well as their connectivity. su2, and the files are in a readable ASCII format. The SU2 mesh format carries an extension of. A description of the mesh and some examples are below. The format is meant to be simple and readable. In keeping with the open-source nature of the project, SU2 relies mostly on its own native mesh format. Details on how to create and use these mesh formats is given below. A converter from CGNS to the native format is also built into SU2. CGNS support can be useful when it is necessary to create complex geometries in a third-party mesh generation package that can export CGNS files. Limited support for the CGNS data format has also been included as an input mesh format. SU2 mainly uses a native mesh file format as input into the various suite components.
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