SMS:CMS-Flow Coverages 11.2

The CMS-Flow interface can utilize two different coverage types. These include:

CMS-Flow: used to create the computational domain (or grid)

This coverage includes a grid frame (reference?) which defines the domain (origin, orientation and extents) and optional feature points, feature arcs and feature polygons.

• CMS-Flow coverage feature points: CMS-Flow supports the option of variable rectangular grid cells. A feature point can be specified as a refine point. The cell sizes will be generated to conform to the specified base cell size and bias for the surrounding refine points (Jeff, we may want to have a picture or two to illustrate how refine points work)

• CMS-Flow coverage feature arcs: Arc options are specified in the Cartesian Grid Arc Options dialog (IDD_CGRID_ARC_OPTS). By default, all cells in the grid can potentially be included in the computation. That means that if the water level exceeds the elevation of the cell (the negative of the depth specified for the cell), the cell will convey flow. However, for computational efficiency, some cells may be flagged to be excluded from the computation. In SMS, these cells are specified as “land” cells and can never become wet or active. The region of the grid to be excluded from computation may be specified using either arcs or polygons (see below). When using arcs, the direction of the arc defines right side as active (water) and the left side as dry (land). Reversing the arc direction swaps the sides. When multiple arcs are used in a CMS-Flow coverage, it is possible for two arcs to classify a cell differently (the cell may be on the land side of one arc and the water side of another). In this situation, SMS will display an error message when the grid is generated.

Attributes include:

• • Generic - the arc is ignored.
  • Percent preference coastline - cells intersected by the arc are classified as land or ocean based on the percentage of the cell on either side of the arc.
  • Land preference coastline - cells intersected by the arc are classified as land. This forces land structures such as jetties into the grid.
  • Ocean preference coastline - cells intersected by the arc are classified as water or ocean. This forces water features such as narrow channels or inlets into the grid.

• CMS-Flow coverage feature polygons: Polygon attributes are specified in the Polygon Attributes dialog (IDD_TELESCOPE_POLYATTS). Feature polygons in a CMS-Flow coverage serve two potential purposes. These include:
  • Cell classification. All cells in the polygon can be disabled by making the polygon a “Land” polygon or allowed to be computational cells by classifying the polygon as “Ocean”. Ocean is the default. This function is similar to the use of arcs described above for the feature arcs.
  • Telescoping grid specification. CMS-Flow also supports a domain consisting of a Telescoping grid (http://www.xmswiki.com/xms/SMS:Telescoping_Grids). This is a variation of a quad tree refinement to allow small cells in areas where higher precision is desired. The user can specify that a polygon is a telescoping size polygon. All cells generated in this polygon will be refined to be no larger than the specified size. When the Map -> 2D Grid command is used for this coverage, if telescoping size polygons exist, the user can choose to use them instead of any specified refine points or the simple grid generation options.

CMS-Flow Save Points (currently described in http://www.xmswiki.com/xms/SMS:CMS-Flow/Save_Points) : used to define special output locations from the computation.

Related Topics

• Coverages
• CMS-Flow