Learning Forum

[Nikita]

In Explicit Dynamics, why is the "Euler Cell Over Emptied"; message issued?

[vganore]

The Euler Cell Over Emptied warning message indicates that a large volume fraction of a material ( > 0.9) is being transported into or out of an Euler cell in a single time step. AUTODYN issues this message to notify the user of potential numerical error caused by transporting excessive material in a single time step. The following recommendations may help alleviate this issue. 1. Use Internal Energy Transport (Global -> Transport). The AUTODYN default is Total Energy Transport. However, in explosive detonation calculations where the detonation products escape into a void at high speed, a better result may be achieved using internal energy transport, because that approach provides a more accurate determination of the internal energy in a cell, which in turn is then used in the explosive equation of state. 2. Increase the minimum Euler density (Material -> Modify -> Cutoffs). The escaping detonation products are typically at very low density. It is useful to limit the diffusion of extremely small masses by increasing this cutoff value. 3.Use a Maximum velocity cutoff of approximately 10,000 m/sec. The predicted velocities of very small masses of material escaping into a void can sometimes be unrealistic. You can limit this behavior by setting the Maximum velocity cutoff using Global -> Cutoffs.