📄 Using the Funnelling Input in MasterSeries

Using the Funnelling Input in MasterSeries

What is funnelling?

Funnelling occurs when two buildings face each other and the wind is forced through the gap between them. This accelerates the airflow, making the external pressure coefficients Cpe more negative (higher suction) than for an isolated building.

This effect is described in BS 6399-2, Clause 2.4.1.4 (also see Clause 3.3.1.1.3 and Figure 12).

When does funnelling apply?

  • Funnelling occurs when the gap width between two opposing façades lies between:

    where b is the building breadth perpendicular to the wind direction.

  • If the gap is less than b/4 or greater than b, treat the building as isolated (no funnelling effect).

How to enter funnelling in MasterSeries

In the “Funn” column, enter a ratio between 0.25 and 1.0:

💡

Enter your Funn value, Hit enter. Click 'Refresh MasterKey Wind Cpe Values'. 

To see the updated pressure click back into W2 row. If your pressure values don't automatically refresh on the graphics, click 'Refresh MasterKey Wind Cpe Values' again.


Change the funn value and click 'Refresh MasterKey Wind Cpe Values'.

  • 0.25 corresponds to a gap of b/4 (onset of funnelling).

  • 1.0 corresponds to a gap of b (no funnelling).

  • The maximum suction effect occurs at a funnelling ratio of 0.5 (gap = b/2).

How MasterSeries calculates funnelling

  • The software uses BS 6399-2, Table 5 to determine modified cpe​ values for zones A, B, and C on the windward walls.

  • The input ratio (0.25–1.0) tells the software where your gap lies in relation to b.

  • MasterSeries then:

    • Applies the appropriate funelling coefficient from Table 5.

    • Interpolates between values when necessary (e.g. for intermediate D/H ratios, as per the note at the foot of Table 5).

Important notes

  • The funnelling ratio can be different for each wind direction, because the building breadth b changes depending on the face the wind is acting on.

  • Always check the geometry carefully for each wind case before entering a ratio.

  • If the structure is not within the funnelling gap limits (<b/4 or >b), enter no value (or 1.0) → building treated as isolated.

In summary:

  • Input = gap / building breadth b.

  • Valid range: 0.25 ≤ Funn ≤ 1.0.

  • Maximum effect = 0.5.

  • MasterSeries applies BS 6399-2, Table 5 with interpolation to compute adjusted cpe.

Related Videos

Jump to 43:40m - Can we take a kind of funneling from nearby buildings (How To Calculate Wind Loading on Building Structures)


Funnelling in MasterKey Wind (Jump to 46m 33s)