Adding porous walls and polygons

Step-by-step guide

Porous walls and polygons represent walls with a specified porosity and height that are used during the 2D simulation process. A porous wall collinear with the boundary of a 2D zone overrides the boundary condition. It is possible to set parameters for the porous wall object that results in the full or partial removal of the wall during a simulation.

This example has a selection of porous walls and porous polygons that have varying properties.

These properties can be viewed or changed in the Properties window.

1. Open the Properties window of the first porous polygon.

2. Note the Porosity value.

This must be a value between 0 and 1, where 0 is impermeable and 1 is fully porous, meaning it has no impact on the flow. As an example, a low porosity in the range of 0.05 - 0.2 may be used to represent a building.

3. Expand the Crest level drop-down to choose from 3 options: Infinite, Height, and Level.

This is the point up to which the porosity applies—above this, there will be no effect.

4. Expand the Remove wall during simulation drop-down, which also has 3 options: Never, Fully, or Partially.

For the Partially option, only faces of the wall meeting the criteria are removed. This option can be used to simulate wall collapse.

5. Select No rainfall to apply no rainfall within the polygon—an option only available for porous polygons.

To best demonstrate the effect of these objects, in this example, a simulation is run with the porous walls and polygons included.

As the water passes through the objects, the porosity takes effect. Those with lower porosity have a higher depth building up behind them and are the first to be removed when the height threshold is reached.