The following Material Point Method (MPM) simulation of sloshing fluid goes “haywire” at the end, just when things are starting to settle down:
(if the animated gif isn’t visible, please wait for it to load)
Similar anomalies have been observed in penetration simulations, where a sudden pressure pulse forms in material that had been once deformed severely but is, at the time of the anomalous pulse, now relatively quiescent. The fundamental reason for this anomaly (much less its resolution) remains an open research question, which is why it is being described here in this blog posting.
The problem definition is provided in WaterColumnKinematicAnomalyProblemStatement.pdf. We challenge (or plead with) the MPM community to articulate proper algorithms that will give realistic and stable solutions to this problem for a range of realistic material property values.