Numerical modeling of complex interfacial physics for the simulation of industrial multifluid processes

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Free surface flows are a common occurrence in industrial fluid mechanics.  Many industrial processes involve the flow of several fluids in complex geometries, and therefore the evolution of the interfaces separating these fluids.  Moreover, it is common to have geometries evolving with time, which influence, sometimes in a very complex way, the dynamics of free surfaces.  For example, hydraulic turbine designers have to take into account the cavitation phenomenon.  When water, in contact with runner blades moving at high velocity, is locally submitted to a pressure drop, the dissolved air nucleates to create bubbles.  This phenomenon is similar to boiling.  The fluid flow then makes the bubbles move from low pressure to higher pressure regions.  The bubbles may then violently implode on or close to a solid surface.  A jet is then created which seems to be the cause for cavitation erosion, i.e. a form of erosion responsible for the mechanical degradation of solid materials by the action of vapor bubbles.  The eroded materials make the moving components not as effective as they should be, which leads to performance loss and important replacement costs.  Direct detection of cavitation is often impossible due to the complicated structure of the enclosure.  The numerical simulation of low Mach number cavitation flows is often the only tool available to hydraulic turbine designers.  This example shows that the accurate modeling of free surface flows can have a significant economical and industrial impact. The main objective of this research project is to develop a numerical model to study the influence of interfacial physics on the dynamics of free surfaces found in complex multiphase flows involving moving boundaries, that are found in industrial applications.  The long term goal of our research program is to provide a general analysis tool for engineers in charge of the optimization of industrial processes involving multiphase systems.