/DT/ALE

Engine Keyword Time step control for ALE or EULER cells.

Format

$Δ T_{s c a}$ $Δ T_{\min}$

Field	Contents	SI Unit Example
$Δ T_{s c a}$	Scale factor on critical time step. Default = 0.5
$Δ T_{\min}$	Minimum time step.

If the ALE time step becomes less than $Δ T_{\min}$ , then the simulation will stop and a restart file will be written.
As of the 2018.0 release, /DT/BRICK and /DT/QUAD are only relevant for Lagrangian elements.
As of the 2018.0 release, time step for ALE or EULER cells can only be controlled with /DT/ALE. This allows the time step control for the ALE cells to be different when you have both Lagrangian and ALE bricks in the input file.
By default, scale factor $Δ T_{s c a}$ is 0.5 which is the recommended value for ALE or EULER cells. As a result, if you did not use /DT or /DT/BRICK or /DT/QUAD with $Δ T_{s c a}$ =0.5, you will have by default, different time step from version 2018.0. To retrieve your previous result, you must set the relevant time step with /DT/ALE.

2017.0 Engine File

2018.0 Engine File

/DT/BRICK with $Δ T_{s c a}$ =0.3

Add /DT/ALE with $Δ T_{s c a}$ =0.3

/DT/QUAD with $Δ T_{s c a}$ =0.0

Add /DT/QUAD with $Δ T_{s c a}$ =0.9

/DT with $Δ T_{s c a}$ =0.4

Not applicable

No time step control

Add /DT/ALE with $Δ T_{s c a}$ =0.9 (3D case), or

$Δ T_{s c a}$ =0.67 (2D case)