Add CFD Boundary

 

When at surface level you can add a CFD boundary in much the same way as a window or any other opening . Please refer to the instructions for the Draw window tool for details on the process of drawing the CFD boundary.

 

Note: There is one important difference with CFD boundaries compared with openings such as windows, which is that the edges of supply/extract boundaries must not coincide with parent surface edges. The CFD boundary should be separated from the surface edges by a distance of at least 0.1 m.

 

 

After selecting the Add CFD boundary tool, the boundary settings are displayed on the Drawing options data panel. You can select the required boundary type from the Boundary type drop list. The following boundary types are available for surfaces of all orientations:

 

 

The following additional boundary types for multi-directional diffusers are available for ceiling and other downward-facing surfaces only:

 

 

Various settings are available depending on the boundary type:

1-Supply:

 

Note 1: the minimum discharge velocity is an important setting in that the diffuser supply velocity in conjunction with the diffuser discharge angle(s) can determine the flow pattern in a space.

Note 2: DesignBuilder CFD can only guarantee minimum discharge velocities for supply diffusers that are located on orthogonal surfaces, that is surfaces that are parallel to the one of the 3 grid axes.

2–Four-way

 

3–Two-way

 

4–Extract

 

5–Temperature

 

6– Flux

 

 

Note: Generally, you should ensure that there are at least three grid cells between a supply boundary and an obstruction (such as a wall, component or assembly), otherwise, during simulation, the flow can ‘lock’ and you will see the mass residual plot forms a flat line with no convergence