Porous Walls
Porous Wall objects are line objects used as part of the mesh generation process carried out when undertaking 2D Modelling. The lines represent walls with a specified porosity and height which are taken into account during the 2D simulation process. Note that a porous wall collinear with the boundary of a 2D zone, will override the boundary condition of the 2D zone along the coincident portion of the boundary. The coincident portions of the wall are considered infinitely high, regardless of any crest level specified.
Porous wall objects are used in SWMM networks but for InfoWorks networks, porous wall functionality has been superseded by the Base Linear Structure (2D). Porous wall objects have, however, been been retained in InfoWorks networks for backwards compatibility.
Porous Wall objects can be imported via the Open Data Import Centre or from AutoCad DWG. Lines can also be digitised directly on the GeoPlan Window.
Porous Wall parameters are edited in the Porous Wall Grid Window of the Lines Grid or the Porous Wall Property Sheet. There are also a number of tools available for editing the geometry of walls. See the Joining and Splitting Lines topic.
Collapsing Walls
It is possible to set parameters for the Porous Wall object which will result in the full or partial removal of the wall during a simulation depending on criteria based on the results of 2D mesh elements adjacent to the wall. The removal of the wall represents the collapse of the wall.
Collapsing Walls Criteria
The criteria to trigger a collapse are defined in fields in the Definition section of the Porous Wall Property Sheet.
See the Porous Wall Data Fields (InfoWorks) and the Porous Wall Data Fields (SWMM) topic for full details.
Remove Wall During Simulation
The Remove wall during simulation option can be set to either Full, Partially or Never.
- Full: if collapse of the wall is triggered, the entire Porous Wall object will be removed from the simulation.
- Partially: if collapse of the wall is triggered, only the portion of the Porous Wall object adjacent to the mesh elements triggering the collapse will be removed from the simulation.
- Never: the wall never collapses.
Wall Removal Trigger
The Wall removal trigger field is used to select the variable to be used to determine whether the wall has collapsed. The trigger variable relates to the results in 2D mesh elements adjacent to the Porous Wall; for example, the Depth option uses depth of water in adjacent elements as the trigger for wall collapse.
Threshold Fields
The Threshold field values to be specified will depend on the trigger variable selected in the Wall removal trigger field.
By default, if the trigger variable in a mesh element adjacent to the Porous Wall exceeds the defined threshold, the wall will collapse.
If the Use difference across wall option is checked, the collapse of the wall will be triggered when the difference between the trigger variable values in the adjacent mesh elements either side of the wall exceeds the defined threshold.
