Research Areas

Fluid Dynamics and Disease Transmission

Flows driven by surface tension are both ubiquitous and diverse. They  play a key role in the transmission of diseases in plants,  animals, and humans via droplet formation and  bubble bursts. The fundamental physical principles underlying such flows provide a unifying framework to interpret the adaptations of the microorganisms, animals, and plants that rely upon them.  Our group's research focuses on a range of problems where droplets, bubbles, interfacial flows, and pathogen-fluid interactions can shape disease transmission and environment contamination (e.g. hospitals). Our approach is to combine direct observations, experiments, and mathematical modeling to describe pathogen transmission from host to host.

  • Drops, Bubbles and Health

    Drops and bubbles can  expose us to diseases and harmful chemicals, or tickle our palate with fresh scents and yeast aromas, such as those distinctly characterizing a glass of champagne. Bubbles and drops are the messengers that can connect us to the depth of the waters and the air that others breath and illustrate the inherent interdependence and connectivity that we have with our surrounding environment. In our research, our group focuses on the particular applications where drops and bubbles have important impacts on the health arena. In particular, we focus on elucidating the physical processes that enable the creation of drops and bubbles and the new challenges that they raise in the presence of pathogens. Among them, the questions of violent expiration emission of droplets within a multiphase cloud; the fragmentation of complex fluids such as mucus and saliva; the interaction of pathogens and fluids that lead to various contamination patterns surrounding an infected host; the creation and selection and change of size of the pathogen-bearing droplets in hospitals. Key words:  droplet transmission, splash, fragmentation, multiphase clouds, pathogen transport, disease transmission, contact, surface contamination, sneezing, coughing, violent expirations, bubble bursting, toilet flushing, nosocomial diseases, respiratory diseases, infectious diseases.

  • Interfacial Flows and Plant Epidemiology

    Plant diseases are a leading cause of crop loss worldwide and are known to be triggered by rainfalls. The interaction between raindrop impact, foliage compliance, and pathogens remain  a black box. The common assumption from phytopathology for such link is that a splash is generated upon impact of raindrops on contaminated liquid films coating sick leaves. Relying on fluid dynamics processes, fluid-structure interactions and interfacial flows, our group focuses on elucidating the mechanisms of disease spread in the field from plant to plant via the lens of interfacial fluid dynamics. Key words:  rainfall, droplet transmission, pathogen transport, disease transmission, foliar diseases, splash, fragmentation, contact, surface-fluid interaction,  infectious diseases, food-borne diseases.

Mathematical Epidemiology and Disease Spread Modeling

Outbreaks of infectious diseases continue to occur with devastating impacts,  threatening  health,  economic and social conditions of millions. The transmission of  pathogens involves a complex interplay between the spatio-temporal dynamics of the host, the ecology of the pathogen, the indoor environment, and human activities. Despite increased monitoring,  control measures for most recurring infectious diseases or new emerging pathogens remain insufficient to mitigate  spread, occurrence, and re-occurence.  This aspect of the  research in the group focuses on revisiting the dynamics of disease spread combining mathematical modeling, data on host or pathogens and new insights gained from our study of the fluid dynamics of disease transmission.

Turbulence and Multiphase Flows

I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics and the other is the turbulent motion of fluids. And about the former I am really rather optimistic. Horace Lamb (1932)

The Komolgorov theory for three-dimensional isotropic and homogeneous turbulent flows relies on dimensional analysis and the observations of turbulent flows showing an energy transfer from the larger to smaller structures of the flow. Observations showed that the energy injected in the larger scales of the turbulent flow is dissipated at the smaller scales. The question is how the energy gets from the large to the small scales. The father of the modern concept of the “energy cascade” is Richardson (1922). His observations led him to propose a multistage process of energy cascade in which the large structures pass their energy onto slightly smaller structures, which in turn pass their energy to even smaller structures, and so on. Although well established,  these results do not describe the full myriad of turbulent flows encountered in practice, and the search for a more complete or unified theoretical approach describing all turbulent flows remains elusive. Whether we consider the terrestrial atmosphere, ocean, mantle, or clouds emitted during sneezes or coughs, turbulence is combined with a complex range of other effects such as rotation, stratification, topography, multiple fluid phases, etc. Understanding their dynamics is surely not just about recreating replicates of these flows, but studying and thus understanding a hierarchy of different but related systems (Hide, 1983). Only then will we be able to truly understand the physical picture governing such flows, and thus possibly predict them. In that spirit, various works on  homogeneous turbulent flows in rotation and multiphase flows are grouped in this section.