SMS:Renumber
Renumbering a mesh improves the computational efficiency (how fast a model produces a result) of a numeric mesh but should not affect the end results.
To renumber a mesh:
- Select a boundary nodestring to start the renumbering process.
- Select Nodestring | Renumber from the SMS menu.
Upon execution of this command, the nodes and elements are renumbered by a wave that passes through the mesh. This wave proceeds from elements connected to the selected nodestring and continues through the entire mesh. If a section of elements or nodes are disjoint, the wave will not continue and a warning message is given. Disjoint mesh sections are assigned arbitrary numbers, but before running the analysis, there should be no disjoint sections. Nodes which are not connected to any elements can be found and selected automatically.
It is important to realize that after renumbering the finite element mesh, any previous boundary condition file or solution file is no longer valid!
Front Width and Band Width
SMS contains two similar algorithms for renumbering a mesh from a boundary nodestring. These algorithms are called the front width option and the band width option. The option to use can be specified in the Nodestring Options dialog.
Due to the number of questions that are asked regarding this subject, this section will attempt to describe, in a broad sense, why renumbering is important.
The finite element solvers use an iterative, banded numerical solver to solve the governing differential equations. If the computer had to simultaneously solve the thousands of equations, it would run out of memory. This is why it uses a banded solver. The front width and the half-band width determine the size of the matrix which is used by the finite element solvers. A smaller front width and band width lead to a smaller required matrix. The front width and band width depend on the node and element numbering of the finite element mesh. To minimize the front width and band width, the mesh should be renumbered.
SMS provides an estimate as to how large the front width and half band width may become when running the finite element solver. These estimates are shown in the Mesh Information dialog, which can be opened by performing the "File | Get Info" command while in the Mesh Module. There is not a single renumbering scheme which always produces the lowest values for these, so it is suggested that you renumber from various locations in the mesh and check the mesh information before deciding which renumbering scheme to use. As a guideline, the mesh should be renumbered using a nodestring which extends across a small section of the mesh, such as a river inflow boundary.
Related Topics
Modules: Mesh Module · Cartesian Grid Module · Scatter Module · Map Module · GIS Module · Particle Module
Models: ADCIRC · BOUSS-2D · CGWAVE · CMS-Flow · CMS-Wave · FESWMS · FVCOM · Generic Mesh Model · GENESIS · HYDRO AS-2D · PTM · SRH-2D · Steering · STWAVE · TABS · TUFLOW
