Our research focus on a wide range of applications of environmental fluid dynamics. We use both observations and modeling to understand turbulence, particle-fluid interactions, and transport phenomena. Our primary research subjects are within water resources, including natural water bodies and engineered water systems. We also collaborate with scientists and physicians to study broader fluid problems.
Current research topics:
Natural seeps of hydrocarbon bubbles from shallow to deep seas
Developing new instrument to better understand marine seeps
Underwater gas blowout in high-speed releases
Turbulence structures in the Missouri River and their influences on transport of fish eggs and larvae
Sediment impacts on freshwater mussels
Understanding mechanisms of environmental transmission of avian flu
Wind-driven seed dispersal and the effect of the seed morphology
Funded by the USGS Aquatic Invasive Species program, we are investigating the effect of turbulence on the egg drift in a unique reach of Missouri River, where a series of channel-training structures and bedforms are present (see upper left figure). We are collaborating with USGS scientists on using observations and modeling to quantify the fine-scale turbulent structures and their influence on the dispersion of egg particles in water.
The lower panel figure shows an example of cross-sectional void fraction calculation from the images. The void fraction map provides quantitative information about the trajectory of release gas and the volume distribution of gas in the water column and the size of fountain when they reach the surface. We will also be able to calculate bubble size distribution as a function of released gas volume so that we can predict how much gas are dissolved in the water, and how much gas can reach to the water surface in such accidents.
Transport and fate of human expiratory droplets play a key role in the transmission of respiratory infectious diseases. The dynamics of virus transmission is not well understood, with one challenge being the complicated fluid and flow characteristics involved in the fate and transport of virus, including source dynamics (e.g., exhale velocity and temperature, droplet sizes, virus load, and droplet–virus correlations), ambient conditions (e.g., mean and turbulent flows, temperature, and humidity), and virus dynamics (e.g., virus viability and infectious rate). Collaborating with experts in influenza virus transmission, we recently developed a fate and transport model to simulate droplet evolution during normal human respiratory activities (talking, coughing, etc.). We improve the model prediction by using a continuous random walk model to better characterize the correlated velocity fluctuations in these respiratory flows.
The simulation shows strong influences of ambient conditions, exhaled velocities and temperatures. The dispersion and evolution of droplets with different initial diameters have very different sensitivity to ambient environments. In the future, we will incorporate the correlation between droplets and viruses to understand the transport of viruses and the risks of exposure at different locations.