Learning Forum

[Babeth]

Hello !

I'm working with Autodyn on Explicit Dynamic.

I was wondering if there is a CFL condition to respect for the time step with this solver, in order to have better results.

Does someone know which method is used in Autodyn ? (Runge Kutta method for exemple)

Or just which CFL condition need to be respected ?

Regards,

Elisabeth

[Chris Quan]

CFL time step is automatically calculated by Autodyn to ensure the stability of explicit time integration.

[Babeth]

So it's not a good idea to change it ? My calculation time is too big on my laptop, can I change this time step respecting the cfl condition ?
Regards Elisabeth

[Chris Quan]

To reduce running time, you need to make sure the End Time in the Analysis Settings is realistic. It is usually in milli-seconds, not seconds. If the End Time has to be in seconds, you may consider to use Transient Structural Analysis system, which allows to use large time steps.
Mass scaling can be used to increase stability time step in the local small elements or very hard materials and thus reduce running time. Mass scaling can be accessed in Time Step Controls under Analysis Settings.
The CFL condition has to be satisfied. Otherwise, results will not be numerically stable.