800k cells will be about 2-3GB RAM (rough estimate) so it's more dependent on the parcel count. The collision models also work with transient particles on a steady flow. Check the model runs OK steady with no particles, then add steady particles to check and then transient particles. Unless the particles cause a major change in the flow then you may not need transient flow.
Segmentation failures can be nondiagnostic. Can you post the residuals up to the point it failed (last few is enough) from the TUI and whether there were any other complaints from the code.
You are navigating away from the AIS Discovery experience