The proposed project is a continuation of an ongoing line of research at NTNU and SINTEF Energy Research aimed at the numerical solution of three-dimensional transient compressible multi-fluid models for multiphase flow. Emphasis will be given to flows wi th particles (i.e. droplets), as encountered in electrocoalescer separators, and the project will aim at calculating such separators. The current project involves improving and developing models for momentum transfer between the phases, and models for elctrocoalesence. The models will be implemented and tested in the SPIDER computational fluid dynamics (CFD) program. The numerical metho d will use compressible, explicit solution with Runge-Kutta integration. The development of three-dimensional multiphase flow models is necessary to improve the design of separators and other process equipment in the oil and gas industry. An improved design tool for multiphase flow in offshore applications has a potential to g ive cost reductions in millions of NOK, as well as large energy savings.