Direct numerical simulations of droplet break-up in turbulence in inertial and viscous regimes

Droplet break-up in complex flows is critical in various environmental and industrial applications, including oil spill mitigation strategies, and the manufacturing of pharmaceuticals and petrochemical products. These problems are characterized by a wide range of scales, from the device and forcing scales to the smallest drops being created, making their modeling challenging and limiting the efficiency of industrial processes. The viscosity of the droplet can vary significantly from one application to another as well as during emulsification processes and can be orders of magnitude larger than the career flow. Understanding the role of the droplet viscosity on the fragmentation dynamics, from the time scale of deformation to the size of the resulting drops being formed remains an active scientific challenge. The present research award will leverage novel computational techniques to resolve complex flows associated with break-up processes, advancing our fundamental knowledge, and informing the development of practical models used in environmental and engineering applications. Direct numerical simulations of the drop break-up processes will be performed, resolving from the smallest scale of the turbulent flow and interfacial feature to the larger scale responsible for initial deformation. The full two-fluids Navier-Stokes equations will be solved, leveraging novel adaptive mesh refinement algorithm to resolve the large range of scales. Large campaigns of simulations will be performed, scanning the physical parameters in order to propose a general theoretical framework describing the role of turbulence, viscosity in the break-up occurrence, time, geometry and mechanisms and the resulting size and number of droplets being produced. These results will then be integrated within population balance models used in environmental and industrial applications. The present award will lead to improved fundamental understanding in break-up of drops in turbulent environment. Through this award, undergraduate and graduate students at Princeton in Engineering and Environmental sciences will be exposed to these critical industrial and environmental challenges that requires research on fundamental multi-phase flows. The use of open-source methods will be promoted through teaching and K-12 outreach activities. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.