When a mesh is generated, a single mesh element may consist of more than one triangle. If a triangle has an area less than the minimum element area specified for the 2D zone, triangles will be aggregated with adjacent triangles until the minimum area is met. However, it is not always possible to meet the minimum element area during aggregation as a model may have, for example, poorly aligned objects or geometric anomalies, which may lead to very small elements in its 2D mesh.
As clusters of such elements can lead to model instability and simulation performance issues, viewing a histogram of the 2D mesh element area/2D mesh element count for selected 2D zones can help you identify small elements and provide a better overview of the mesh for the selected 2D zones. If you find any small elements, you may decide, for example, to change the minimum element size for a 2D zone or to alter the zone's geometry in order to refine your model.
To generate a histogram, ICM uses the largest area of all 2D mesh element areas in the selected 2D zones as the initial maximum 2D mesh element area, and assigns 0 as the minimum area. It then subdivides the initial maximum area into equal-sized intervals (bins). By default, the number of bins is 10. It then finds the number of elements for each binned mesh area, and displays them in a dialog as the 2D mesh element area/2D mesh element count histogram and grid. An example is shown below:
Both the grid and the histogram are selectable. If you select a row in the grid, the corresponding bin is highlighted in the histogram. Similarly, you can double-click on a bin in the histogram to select the corresponding row in the grid.
The 2D Mesh Element Histogram dialog can also be used to:
- Limit the range of the 2D mesh element area being inspected by specifying a minimum and /or maximum area.
- Drill-down for closer inspection of a selected binned mesh element area using the Set min/max from selected bin button.
- Revert the minimum and maximum 2D mesh element areas to their initial minimum and maximum area range after you have drilled-down.
- Display logarithmic values, rather than linear values, for the 2D mesh element counts in the histogram.
- Display a Results Analysis grid view of a selected row or histogram bin. For every element in the selected element area, a read-only Results element 2D object is generated with their 2D Zone ID, 2D mesh element number, Area, Ground level and Roughness listed in the Results Analysis grid. You can use the Results Analysis grid to display an element's properties and to find an element in the GeoPlan.
To view a histogram
- In the GeoPlan, select one or more InfoWorks or SWMM 2D zones that you want to inspect for any element areas that are smaller than the Minimum element area specified for its properties.
- Select the Histogram for 2D element areas option from the Model
Meshing menu.
The 2D Mesh Element Histogram dialog is displayed, which contains the 2D mesh element area/count histogram and grid based on the initial minimum and maximum area and number of bins.
Tip: If there is a very large range in element count values for different bins, check the Logarithmic scale box to display logarithmic rather than linear values on the Y axis. - To limit the range of the 2D mesh element areas being inspected:
- Specify the minimum area to be inspected in the Min area field.
- Specify the maximum area to be inspected in the Max area field.
Tip: As the purpose of histogram is to help you identify very small areas in the 2D mesh, you may find it useful to set the Max area to the Minimum element area specified for the 2D zone.
The grid and histogram are updated accordingly.
- For closer inspection of an area:
- Use the up arrow to increase the number of bins. The maximum number of bins is 100.
- If there is a particular area that you'd like to inspect further, select the applicable row on the grid, and then click Set min/max from selected bin.
Note: There must be a non-zero value in the 2D mesh element count column in the selected row.Tip: You can use the Set min/max from selected bin button multiple times until it is no longer possible to drill down any further. The button is disabled when this occurs.
The grid and histogram are updated accordingly.
- When you find an area that has elements that you want examine further in the
Results Analysis grid, select the applicable row or bar in the dialog, and click Show grid view.
Tip: For optimum performance, it is recommended that the element count is less than 100,000.
A progress bar is displayed while the Results element 2D objects are being generated.
- To view the properties of a particular element and find it on the GeoPlan:
- Right-click on the relevant Results Analysis grid row
- Select Properties from the popup menu
A 2D Zone Mesh Element Properties dialog is displayed for the selected element.
- Click Find in GeoPlan to highlight the mesh element in the 2D mesh in the GeoPlan.
Tip:- You can use the Select and Find in GeoPlan option from the popup grid menu, if you only want to highlight the mesh element in the GeoPlan without displaying its properties.
- You can save the Result element 2D objects as a Results analysis database item. See Results Analysis for details.
- Click Close in the 2D Zone Mesh Element Properties dialog when you are finished looking at the element properties.
- Repeat Step 6 if you want to view the properties of another element in the Results Analysis grid.
- When you are finished looking at the Results Analysis grid, click
(Close).
- If you want to investigate another element area in the histogram:
- Click Reset full min/max range to revert the mesh element areas being inspected to their initial maximum and minimum values.
- Use the methods described in Step 3 and 5 4 refine your inspection.
- When you have finished inspecting mesh element areas, click Close, in the 2D Mesh Element Histogram dialog.