There are numerous situations where the gas cloud shape is not a just a regular box. A typical example is a release filling two rooms connected by a door. In this case, multiple clouds have to be defined.

Define multiple gas clouds

A single gas cloud can be defined in the Gas composition and volume section in the CASD scenario menu. When you want to define multiple gas clouds, you have to do so in a separate section called Multiple or custom gas cloud. This section is by default not shown in the scenario menu. To show the section, you need to right-click on the top in the white area of the scenario sidebar, and enable the section in the context menu.

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How to enable the Multiple or custom gas cloud in the CASD scenario menu

The simplest way to create a new cloud is to right-click in the white area and choose Create cloud.

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Create a new cloud

A window will open where you can fill in the cloud characteristics such as shape, position, rotation, size, subdivision, and fuel mass fraction. Most of the parameters are self-explanatory. The parameter subdivision denotes the number of planar surfaces a shape is divided into; it is used for curved shapes.

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Create a new gas cloud characteristics window

You can add multiple clouds by repeating the above procedure, creating one cloud at a time filling in the necessary parameters (shape, position, etc.).
Alternatively, you can right-click on the cloud and click on Arrange in grid.

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Adding multiple gas clouds by using the Arrange in grid option

A window opens where you can arrange multiple clouds in a 3D array, within a plane, along a line or in a custom shape.

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Arrange multiple clouds in a 3D array, within a plane, along a line or in a custom shape