Error using corss sectional area.

[toni.ho...@gmail.com]

Hello friends!

I am trying to use the variable cross section to represent a building with a pitched roof.

In the CEdit menu I can't type 0 as the top cross sectional area.

If I type 0 m2 through the text editor or a close number like 0.00001 in CEdit, then the model represented in smokeview is different from the real model. The sizes of the rooms are different

This is the real model

This is the model with corss sectional area

!! Compartments 

&COMP ID = 'DH11'

      DEPTH = 17.8 HEIGHT = 11.1 WIDTH = 79.7

      CEILING_MATL_ID = 'TEJA' CEILING_THICKNESS = 0.03 WALL_MATL_ID = 'PP' WALL_THICKNESS = 0.2 FLOOR_MATL_ID = 'SOL' FLOOR_THICKNESS = 0.3

      CROSS_SECT_AREAS = 1418.66, 1418.66, 0.1

      CROSS_SECT_HEIGHTS = 0, 6.9, 11.1

      ORIGIN = 0, 11.7, 0 GRID = 50, 50, 50 /

&COMP ID = 'DH21'

      DEPTH = 11.7 HEIGHT = 9.6 WIDTH = 79.7

      CEILING_MATL_ID = 'TEJA' CEILING_THICKNESS = 0.03 WALL_MATL_ID = 'PP' WALL_THICKNESS = 0.2 FLOOR_MATL_ID = 'SOL' FLOOR_THICKNESS = 0.2

      CROSS_SECT_AREAS = 932.49, 932.49, 0.1

      CROSS_SECT_HEIGHTS = 0, 6.9, 9.6

      ORIGIN = 0, 0, 0 GRID = 50, 50, 50 /

Any clue?

Thanks in advance

[Richard Peacock]

You are correct, CFAST does not allow a zero in the cross-sectional area (to avoid a divide by zero in the general case), but smokeview, in general, does not visualize the cross-sectional area. Rather, it just visualizes the overall volume, adjusting the length and width (maintaining the aspect ratio) and keeping the height the same as the base compartment height.  CFAST itself does a more complex calculation to determine the layer height consistent with the user input of area ad a function of height.