Fluid Dynamics and Disease Projects

Fluid fragmentation shapes rain-induced foliar disease transmission

Plant diseases represent a growing threat to the global food supply. The factors contributing to pathogen transmission from plant to plant remain poorly understood. Statistical correlations between rainfalls and plant disease outbreaks were reported; however, the detailed mechanisms linking the two were relegated to a black box. In this combined experimental and theoretical study, we focus on the impact dynamics of raindrops on infected leaves, one drop at a time. We find that the deposition range of most of the pathogen-bearing droplets is constrained by a hydrodynamical condition and we... more

Rain-induced foliar pathogen ejection

Plant diseases are a major cause of losses of crops worldwide. Although rainfalls and foliar disease outbreaks are correlated, the detailed mechanism explaining their link remains poorly understood. 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. We examine this assumption using direct high-speed visualizations of the interactions of raindrops and leaves over a range of plants. We show that films are seldom found on the surface of common leaves. We quantify the leaf- surface’s... more

Interactions between bubbles and microorganisms

Bubbles are ubiquitous in biological environments, emerging during the complex dynamics of waves breaking in the open oceans or being intentionally formed in bioreactors. From formation, through motion, until death, bubbles play a critical role in the oxygenation and mixing of natural and artificial ecosystems. However, their life is also greatly influenced by the environments in which they emerge. This interaction between bubbles and microorganisms is a subtle affair in which surface tension plays a critical role. Indeed, it shapes the role of bubbles in mixing or oxygenating... more

Surface-tension phenomena in organismal biology: human

Flows driven by surface tension are both ubiquitous and diverse, involving the drinking of birds and bees, the flow of xylem in plants, the impact of raindrops on animals, respiration in humans, and the transmission of diseases in plants and animals, including humans. 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. The symposium on ‘‘Surface-Tension Phenomena in Organismal Biology’’ assembled an interdisciplinary group of researchers to address a large... more

Violent Expirations: importance of the turbulent multiphase flow

Violent respiratory events such as coughs and sneezes play a key role in transferring respiratory diseases between infectious and susceptible individuals. We present the results of a combined experimental and theoretical investigation of the fluid dynamics of such violent expiratory events. Direct observation of sneezing and coughing events reveals that such flows are multiphase turbulent buoyant clouds with suspended droplets of various sizes. Our observations guide the development of an accompanying theoretical model of pathogen-bearing droplets interacting with a turbulent buoyant... more

Fluid fragmentation from hospital toilets

Hospital-acquired infections represent significant health and financial burdens to society. Clostridium difficile (C. difficile) is a particularly challenging bacteria with the potential to cause severe diarrhea and death. One mode of transmission for C. difficile, as well as other pathogens, which has received little attention is the potential air contamination by pathogen-bearing droplets emanating from toilets. In the fluid dynamics video submitted to the APS DFD Gallery of Fluid Motion 2013, we present flow visualizations via high-speed recordings showing the capture of the product of... more

Surface-tension phenomena in organismal biology: plants

Flows driven by surface tension are both ubiquitous and diverse, involving the drinking of birds and bees, the flow of xylem in plants, the impact of raindrops on animals, respiration in humans, and the transmission of diseases in plants and animals, including humans. 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. The symposium on ‘‘Surface-Tension Phenomena in Organismal Biology’’ assembled an interdisciplinary group of researchers to address a large... more

Drops and bubbles in the environment

Bubbles and drops are ubiquitous in nature and play critical roles in many important environmental processes. Most familiar is the life-sustaining role of rain. Less familiar are their roles in the thermal budget of the atmosphere and their role in pathogen dispersal. In this paper, we highlight new  applications where drops and bubbles have important impacts on the environment and health arenas. The paper highlights the physical processes that enable the creation of drops and bubbles and the new challenges that they raise. Among them, we discuss, in particular, the role of drops and... more