Abstract
This paper analyses the approach of using a two-pressure two-fluid model with instantaneous pressure relaxation, comparing it to the more traditional approach of using a single-pressure two-fluid model. To do that, the multi-stage centred (MUSTA) scheme for non-conservative two-fluid models of Munkejord, Evje and Flåtten [Submitted, 2008] is applied to and tested for the two-pressure two-fluid model. Within this framework, example calculations show that from a modelling point of view, using the two-pressure two-fluid model with instantaneous pressure relaxation is not different from using the single-pressure two-fluid model. From a computational point of view, however, the former approach has the significant disadvantage of introducing a large amount of numerical smearing.