Boundary conditions

In the Boundary condition menu, you must specify boundary conditions for the outer boundaries of the simulation domain. The lower boundaries in X, Y, and Z directions are denoted by XLO, YLO and ZLO respectively, and the upper boundaries likewise by XHI, YHI, ZHI.

Recommended boundary conditions are as follows: 

• EULER: uses the Euler equations, should be used for most explosion scenarios

• NOZZLE: the most robust boundary condition for wind and dispersion scenarios

• PLANE WAVE: for explosions in low confinement and for far field blast propagation, the boundary must be positioned far from the explosion

• WIND: Wind inflow or outflow 

• SYMMETRY: generally not used for realistic geometries

• EQCHAR: not recommended

• BERNOULLI: not recommended

By default, Euler boundary conditions are selected for explosion scenarios. For dispersion scenarios, nozzle boundary conditions are applied by default. When wind is defined in CASD using the Wind Wizard, the wind boundary condition will automatically be applied to the appropriate boundary.

For modelling the surface of the sea or ground, it is recommended to use a solid surface together with either the EULER or the NOZZLE boundary condition.

Setting wind conditions

Wind conditions can be defined using the boundary conditions tab however, the use of the Wind Wizard in the Scenario Settings tab is recommended. 

Running an explosion simulation based on dispersion dump file

The boundary conditions from the dispersion setup should be maintained. Changes to the boundary conditions can lead to non-physical behaviour. Ensure that grid boundaries are sufficiently far away from the explosion to allow the pressure wave to develop without interacting with the boundary.