Based on improved understanding of multi-phase physics, large-scale experiments and field data, a new transient multi-phase flow simulator concept using leading edge technology will be developed. This knowledge can be applied to understand complex multi-phase flows in large diameter pipelines and sections with complex geometries relevant to upstream production. Further, LEDA- software will model long pipelines and simulate two- and three phase flows relevant to deepwater upstream development. The LEDA- program will develop the modelling- and simulation software needed to design deepwater pipelines of tomorrow.