The success of the series of International Conferences on Multiphase Flow, Orlando, Florida (2001); Santa Fe, New Mexico (2003), Portland, Maine (2005), Bologna, (2007), New Forest, UK (2009), Koss, Greece (2011) and A Coruna, Spain (2013) has led to reconvening the meeting in 2015. The overall focus of this conference series is the combination of experimental and computational techniques to gain a better understanding of all classes of multiphase and complex flow. The goal of the meeting is to facilitate the exchange of ideas and experiences directly and interactively, thereby promoting the development of knowledge in this increasingly important topic. Fluid dynamics processes in nature are essentially multi-phased, i.e. involving more than one phase of a component such as liquid, gas or plasma. The range of related problems of interest is vast: astrophysics, biology, geophysics, atmospheric process and many others including a whole variety of engineering applications. Thus it is understandable that multiphase structures generate a great deal of interest. This is the motivation for experimental, analytical and numerical studies in this area. While progress is continuing in all three categories, work on numerical solutions has advanced rapidly, owing to the continuing improvements in computer power and the software tools available to researchers. Progress in numerical methods has not only allowed for the solution of many practical problems, but also helped to advance our understanding of the physics involved. Many unresolved issues are inherent in the very definition of multiphase flow, where it is necessary to consider coupled process in multiple scales, not necessarily all of them characterised by the same physics. Moreover, in the study of some of them, the approximations valid for large scale problems may no longer be physically appropriate. Close interaction between numerical modellers and other researchers is required to resolve many outstanding issues in multiphase flow. Theory and experiments are essential for validation and verification of numerical methods, with the latter providing new insights into the interpretation of experimental results and suggesting new directions of theoretical research.