Ignition

The ignition location can be set by expanding the Ignition tab in CASD. The following ignition properties can be defined:

• Position: should be located in the centre of a control volume within the cloud volume. It is not recommended to ignite inside a partially blocked control volume.

• Dimension: can be a point (0D), a line (1D), a plane (2D) or a volume (3D). For gas explosions a point ignition is normally used to simulate a spark ignition. For fire simulations, a large ignition region has less effect on the overall results and is recommended for easier ignition.

• Time of ignition: should normally be zero for gas explosions. For fire scenarios a reasonable delay should be implemented to allow for some gas accumulation. For jet leaks a typical time would be 0.1-0.25s and 0.5-2s for a diffuse leak.

• Duration of ignition: a non-zero duration is highly recommended for fire simulations.

Below is an example of setting an ignition location for an explosion scenario. The ignition location is set within the fuel region and within the centre of a cell where the grid cell size is 0.5m. Dimension, time and duration are kept as default values of zero as is recommended for explosion scenarios.