boundary conditions - firetools/blenderfds GitHub Wiki

ℹ️ Updated to BlenderFDS 6.0.x

This wiki page explains how to set and link boundary conditions to the object geometries.

• The Blender Object and its Material data-blocks
• Setting the boundary condition of OBST and VENT namelists
• Setting the boundary conditions of GEOM namelists
• Disappearing SURF

Blender Material data-blocks controls the appearance of a Blender Object: its color, texture, and how the light interacts with it. The shape of each object can be decorated by one or more materials. At the very top of the Material tab of the Properties panel, you find the material slots, the list of all the materials that are referenced by the object and can be used to set the appearance of the shape faces. When looking at the list of the material slots, the currently selected slot sets the active material.

As with all Blender data-blocks, even Blender Material data-blocks can be shared between objects and .blend files.

BlenderFDS uses those same materials to define the boundary conditions, both exporting/importing the related SURF namelists, and appling them to certain namelists with the SURF_ID parameter.

In BlenderFDS, the active material of the object with OBST and VENT namelists is exported as its SURF_ID boundary condition.

The Material tab of the Properties panel contains the parameters of the linked SURF namelists.

By default, the SURF namelist gets exported only when called by any of the exported objects.

Here is an example of the exported FDS namelists:

&SURF ID='Burner bc' RGB=255,0,0 HRRPUA=500.0 /
&VENT ID='Burner' SURF_ID='Burner bc' XB=-1.,1.,-1.,1.,1.,1. /

Conversely, the SURF_IDS and SURF_ID6 parameters of the OBST namelist are not supported. If you need to define different boundary conditions on the faces of an OBST parallelepiped, add one or more VENTs over the appropriate faces.

The GEOM geometric namelist extends the traditional OBST box-shaped obstacle to a generic-shaped obstacle in the fluid domain, as shown in the Geometries wiki page.

A different boundary condition can be assigned to each face of the triangulated surface. The available boundary conditions are linked into the GEOM line by the SURF_ID parameter. Then they are assigned to each face by an index in the FACES parameter. See the FDS User's Guide for further details.

BlenderFDS can export/import the index pointing to the right SURF namelist for each face.

In the case of GEOMs, you can add as many boundary conditions as you like to the object by adding Blender Material data-blocks to its Material slots, and then assign those boundary conditions to each of the faces of the object shape.

The following screencast shows how to add a new Material to the Material slots and then assign that boundary condition to a few faces of the Object shape.

Here is an example of the exported FDS namelists:

&SURF ID='Burner bc' RGB=255,0,0 HRRPUA=500.0 /
&GEOM ID='Example' SURF_ID='INERT','Burner bc' BINGEOM_FILE=... /

When saving, Blender removes unused datablocks. So if the Blender Material that exports a certain SURF namelist is not referenced by any Blender Object it is automatically purged. You can prevent its removal by setting the Fake User shield in the Material Property tab.

See the following page of the Blender docs for further details.