Defining Porous Regions

 

What are Porous Regions?

in:Flux allows users to define a porosity volume to replace CAD pieces. This feature can be used when your project has CAD items such as:

  • grated decks

  • pipe racks or complex pipework

  • louvers

 

Rather than having the CFD code spend extra time refining calculations in and around these complex areas, porosity replaces the region with an equivalent volume which allows a percentage of the flow to travel through.

  • This percentage is defined as a value between 0 and 1

  • A value of 1 represents a fully open volume, as if the CAD pieces did not exist at all

  • A value of 0 represents a closed fully solid volume

 

 

Types of Porous Regions used in in:Flux?

Grated Deck: Area-based porosity

  • Defined as an axis-aligned cuboid region with a porosity value in one direction (x, y, or z)

  • For most all cases, grated decks will have a porosity value entered in the z-direction

  • A porosity value of z=0.9 is typical for grated decks

 

Porous Region: Volume-based porosity

  • Useful for non-grated deck applications where the porosity value is applied in all directions throughout the defined volume

  • A rotation value can be applied to the porous region volume to rotate the volume off-axis

 

 

How to Define a Porous Region in in:Flux?

The following adds a porous region to act as a grated deck using area based porosity. From the Add Items Tab, select “Porous Region” from the available options, located under Geometry

 

 

When you define a porous region, all geometry within that region is disregarded i.e. the porous region replaces the geometry. Thus, for a grated deck you must position the porous region only over the geometry that is representing the grating. In the figure below, a solid deck was modeled in the CAD geometry instead of a grated deck. To define the deck to be grated in in:Flux, the porous region option was selected from the Add Items Tab and two opposing points for region were selected using the pick-tool (as would be done for a monitor region). The preview was used to verify the thickness of the porous regions encompassed the geometry representing the plating of the deck and was not inclusive of the structure.

 

 

When the porous region is added to the project it will appear as translucent yellow in the 3D window and will appear in the Project Items Tab under the geometry options. Now when ventilation and dispersion simulations are calculated this region will use the porosity value entered rather than the defined geometry.

 

For complex decks, multiple cuboid regions can be defined. In the below example five porous regions were defined.

 

 

Important Note: if you define a porous region after simulations have finished calculating, you will need to rerun them.