Centrum voor Wiskunde en Informatica Modelling, Analysis and Simulation Riemann-problem and level-set approaches for two-fluid flow computations I. Linearized Godunov scheme B. Koren, M.R. Lewis, E.H. van Brummelen, B. van Leer REPORT MAS-R0112 AUGUST 2001 MAS Modelling, Analysis and Simulation