Numerical simulations of turbulent liquid-liquid dispersions with quadrature-based moment methods

The accurate description of droplet dynamics in turbulent liquid-liquid dispersions is of great importance in many industrial applications, especially when the economy of the process is determined by the involved mass transfer and chemical reaction rates. In this respect, the proper estimation of the spatial and time evolution of the droplet polydispersity can offer a useful tool to the modeler to design and scale-up relevant processes. In the latest years, computational fluid dynamics (CFD) and population balance modeling (PBM) have been coupled into a single computational tool, paving the way to full-predictive macro-scale models that incorporate sub-models for describing the rate of the relevant phenomena occurring at droplet-scale, such as coalescence, breakage, momentum and mass exchange with the continuous phase. In this work our recent advances on this topic are presented, with a particular attention to two distinct elements: 1) the choice of appropriate coalescence and breakage closures, pointing out the need to account for high-order turbulent phenomena, such as turbulent intermittency through the use of the so-called multifractal formalism; 2) the possibility to carry out simplified spatially homogeneous simulations when there is a clear separation of scales between coalescence/breakage and mixing. CFD simulations were carried out with our own implementation of the Quadrature Method of Moments (QMOM), combined with the two-fluid model, present in a solver of the open-source code OpenFOAM