Modelling and Computation of Interfaces in Turbulent Multiphase Flows
Abstract: Droplets carried in turbulent fluids rely, for their existence, on tiny interfaces. Interfaces are not property of the drop or of the the carrier fluid and are inherently a non-place. However, in environmental and industrial processes, their role is enormously important since it is across the interfaces that momentum, heat and mass transfer fluxes coupling the drop to the carrier fluid occur: the accurate determination of their position, shape and interaction with the fluid turbulence is crucial to predict physical phenomena, and industrial and environmental processes. To this aim, Direct Numerical Simulation (DNS) of turbulence and accurate tracking of the interface are required, but the range of scales involved for most ofpractical environmental and industrial applications is so wide that performing this task is a formidable challenge for present day computers: The grid resolution for DNS of turbulence is of the order of the Kolmogorov scale, but of course physical interfaces have a much smaller scale (order of few molecules) making the direct resolution unfeasible. In this talk, we will briefly review the current computational methodologies used to interfaces and the we will focus on the phase-field approach in turbulent flows: In this Eulerian approch, the phase distribution is described by the order parameter φ. We will examine several flow instances and phenomena ranging from turbulent stratified flows to turbulent dispersion of drops and bubbles so to reveal potentials and limitations of the phase-field method. Interface interactions with turbulence, coalescence and
breakup phenomena for different values of fluids density and viscosity will be discussed in connection with the characteristics of turbulence. Finally, the physics modelling and the method required to include the effect of surfactants will also be examined.
Prochains évènements
Voir l'agendaWebinaire Rui Ni
The Wrath of the Small: Fragmentation of Bubbles in Turbulence by Small Eddies
Rui Ni est Assitant Professor en Engineering à l'Université Johns Hopkins (JHU) et a été nommé professeur DOE ORISE en 2019. Avant de rejoindre JHU, il était titulaire de la chaire Kenneth K. Kuo à la Penn State University. Il a obtenu son doctorat au département de physique de l'Université Chinoise de Hong Kong en 2011, et a travaillé comme chercheur postdoctoral à Yale et à l'Université Wesleyan. Il a reçu une bourse CAREER de la NSF dans le domaine de la dynamique des fluides, une bourse de jeune chercheur de l'ACS-PRF et une bourse Early Stage Investigation de la NASA. Ses recherches portent principalement sur le développement de méthodes expérimentales avancées pour comprendre les écoulements multiphasiques dans de nombreuses applications, telles que les systèmes énergétiques, les émulsions, l'ingestion de particules dans les turbines à gaz, les atterrissages sur des corps extraterrestres et l'atténuation des poussières pour les futures explorations spatiales.