Porous objects such as grated decks and walls are commonly encountered in facilities. In addition, porous volumes may be used to represent partially open/closed objects such as heat exchangers.
For a general introduction to working with a geometry database and define new objects please read the article on Working with a geometry database.

Define a grating in CASD

To define a primitive to be a grating, open the primitive in an Object window, open the window’s Edit menu and choose Properties. Alternatively press the letter “P” in the keyboard to show the Parameters window.

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Open the Properties menu from the Edit menu in CASD

In the Parameters window you need to make sure that both the volume and area porosities are set to the desired value. In the case of a thin plate, make sure the porosity in the direction perpendicular to the plate is set to the correct value.

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How to set the area and volume porosities

It is good practice to adopt a convention regarding the material (Hue/Colour) for grated decks or walls, in order to visually differentiate the grated and plated bulkheads. Gexcon’s typical material for grated decks is Hue=60 (Yellow) while that of solid decks is Hue=0 (Red).

FLACS also has a special grating model that can be used for modelling flow through the grating in dispersion and ventilation simulations. Such grating objects should not be used for explosion simulations as they do not represent the flame acceleration along the grating correctly.