Wed, Nov 01, 2017 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Antonino Ferrante, Associate Professor, University of Washington
Talk Title: On the Physical Mechanisms of Droplet/Turbulence Interaction
Abstract: The interactions of liquid droplets with turbulence are relevant to both environmental flows and engineering applications, e.g., rain formation and spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown. The main goal of this research is to investigate the physical mechanisms of droplet-turbulence interaction for both non-evaporating and evaporating droplets.
Droplets in turbulent flows behave differently from solid particles, e.g., droplets deform, break up, coalesce and have internal fluid circulation. We have developed a new pressure-correction method for simulating incompressible two-fluid flows with large density and viscosity ratios. The method's main advantage is that, for example, on a 10243 mesh, our new pressure--correction method using the FFT-based parallel Poisson solver is forty times faster than the standard method using multigrid. In general, the new pressure-correction method could be coupled with other interface advection methods such as level-set, phase-field, or front-tracking. We have coupled the pressure-correction method with a volume-of-fluid method for its properties of being mass conserving and sharp-capturing of the interface.
We performed direct numerical simulation (DNS) of finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale in decaying isotropic turbulence. We studied the effects of Weber number, viscosity ratio and density ratio. We derived the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. This allows us to explain the pathways for TKE exchange between the carrier turbulent flow and the flow inside the droplet. The role of the interfacial surface energy is explained through the power of surface tension term of the two-fluid TKE equation. Also, we derive the relationship between the power of surface tension and the rate of change of total droplet surface area. This allows us to explain how droplet deformation, breakup and coalescence plays a role on the temporal evolution of TKE. Our DNS results show that increasing Weber number, the droplet to fluid density or viscosity ratios increases the decay rate of the two-fluid TKE relative to that of single-phase flow. Via analysis of the DNS results, the revealed physical mechanisms will be presented.
Recently, we have also extended the volume-of-fluid method to simulate evaporating droplets. The verification and validation of the method and the DNS results will be presented in comparison to theory and experiments.
Biography: Antonino Ferrante is an Associate Professor of the William E. Boeing Department of Aeronautics & Astronautics at the University of Washington (UW). In 2004, he received the Ph.D. in Mechanical and Aerospace Engineering from the University of California, Irvine, where he continued his research as Postdoctoral Scholar until 2007. From 2007 to 2009, he was Postdoctoral Scholar in Aeronautics at the California Institute of Technology at GALCIT. In 2009, he joined the UW as Assistant Professor where was tenured in 2015. Ferrante is recipient of the NSF CAREER Award (2011). His research is focused to the understanding of the physical mechanisms of complex flows, e.g. multiphase and wall-bounded turbulent flows, and enable that through the development of parallel computational methodologies for simulating such flows on supercomputers.
Host: Department of Aerospace and Mechanical Engineering
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Posted By: Ashleen Knutsen