Establishing next-generation pioneering models for interface mass transfer, breakup and coalescence in turbulent flow

A variety of industrial processes rely on or have challenges with the presence of bubbles or drops dispersed in a liquid. Many of these industrial processes operate the system such that the liquid with the dispersed bubbles or drops are flowing in a turbulent/chaotic manner. Although the chaotic nature of the turbulent flow, we believe that there exists a certain organized structure in the flow that can be described mathematically. Yet, we have not understood how these organized flow structures interact with the bubbles or drops to deform and possible fragment these. We neither understand the role of the organized flow structures in the molecular transport across the boundary between the bubble/drop and the surrounding liquid. This project has initiated studies that will reveal fundamental understanding of dispersed multiphase flows. Qualitative causality between flow structures and droplets has been uncovered in the project's initial phase. These results will be reported in a scientific article. The project's initial phase has further developed numerical methods for detailed simulations of phase transitions in dispersed multiphase flows, and these numerical further developments will be reported in a scientific article. Numerical simulation results have been generated and will be analyzed to reveal the relationship between phase transition and flow structures. The ultimate goal of the project is to use the new knowledge to propose a completely new basis for next-generation models for droplet/bubble breakup and mass transport across phase boundaries. The results initially achieved in the project have been communicated through participation in two international conferences. Project meetings have also been arranged with international partners.

Turbulence plays an enormous importance in many industrial applications. In industries concerned with dispersed drops-in-liquid or bubble-in-liquid flow, the drops/bubbles may fragment (the breakup phenomenon), merge (the coalescence phenomenon), or undergo phase transition (the interface mass transfer phenomenon). The available (CFD) models for these phenomena share the common feature that they are based on simplistic hypothesis for how turbulence interacts with the drop/bubble interface. The absent understanding of the mechanisms of turbulence-interface interactions constitutes a bottleneck for developing predictive models. Our underdeveloped understanding of these mechanisms has remained since the first proposed models; thus, constituting a nearly half-century-old problem. With the significant development of numerical methods and computational capacities in recent years, this model problem can finally be addressed. This project will break with the old traditions, and approaches the modelling of turbulence in interface mass transfer, breakup, and coalescence from a wholly new direction. For the first time the underlying mechanisms for turbulence-interface interactions will be uncovered. This will be a breakthrough in our physical understanding and allow a new theoretical foundation for developing the models for interface mass transfer, breakup, and coalescence without today's gross limitation. The ultimate results from this project is to establish the next-generation framework for modellers and users of CFD who are concerned with turbulent dispersed flow. This project certainly addresses a hard problem and its realization requires an interdisciplinary approach. It has thus been a great emphasis on international collaboration to enable the ambiguous scientific advancements of the project.