Refinement of the Mass Conservation Algorithm Used in CATHENA

Abstract

The need to correct mass conservation errors is an integral part of the numerics underlying CATHENA. In the past, it was found necessary for stability reasons to neglect mass conservation errors when the code ran at the minimum time step or a re-do occurred. This could potentially lead to significant discrepancies in fluid inventory during some simulations. In CATHENA MOD-3.5b/Rev 0, a revised mass conservation strategy was implemented that addresses the weaknesses of the previous strategy. Mass is now conserved at all times, and a redistribution strategy has been implemented to ensure numerical stability when rapidly varying conditions could lead to node overfilling. This work outlines the refined algorithm, and illustrates its effectiveness.