Research

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:

Hydrocarbon release from the sea floor is a vertical transport mechanism and the dynamical process between water and bubbles determines the maximal height of rise. This is an important process to ocean biogeochemistry, microbial population, and ecosystem structures. Understanding seep dynamics also has significant implications on the fate and transport of oil and gas particles in oceans. 
Funded by the National Science Foundation (NSF), we conducted field observations of natural seeps at Green Canyon (GC) 185, collected rich data using our newly developed RPiPIV system, along with measurements of gas flux and acoustic backsatter from bubbles using several single-beam and multi-beam echo-sounders mounted on the research vessel and two underwater robots (AUV Sentry and ROV Jason).  
Transport of Carp Eggs in Large Rivers
Invasive carps often spawn in high turbulence areas of rivers.  The eggs are initially small and dense, which requires substantial turbulence to keep them suspended. While drifting downstream, they increase their volume by taking on large amount of water and approach a near-neutrally buoyant density (slightly heavier than water) before hatching. In large rivers, highly three dimensional turbulence are present. Along with the current in the rivers, they dominate the location, timing of the dispersion of carp eggs in rivers, which serves the critical role in survival of these eggs.
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. 
Dispersal of grass seeds in wind 
Grasses are ubiquitous components of the natural and human-influenced environment, covering as much as 40% of the Earth's land surface. This global distribution reflects their ability to disperse their seeds. While the major domesticated grasses have been selected for their large seeds and high nutritional value, most of the more than 11,000 species of grasses have tiny seeds, which may be subject to dispersal by wind. The seeds are enclosed in papery leaf-like structures or bracts (glumes and lemmas), one of which bears a long tail-like appendage known as an awn; together the seed plus the bracts and awn form the spikelet, which is the dispersal unit.
We studied the flight dynamics of a bent-awn plumegrass called Saccharum contortum. We applied both laboratory experiments and numerical simulations. The goal of this study is to determine how the tiny hairs can affect the seed drag in various wind conditions. From experiment, we found that the Saccharum contortum seeds have a terminal free fall velocity primarily in the range of 1–2 m/s. The seed lacking hairs exhibited a significantly higher terminal velocity, reaching 2.34 times the average velocity observed in seeds with hairs. For seeds with hairs, terminal velocity exhibited a linear relationship with seed mass, while the drag coefficient displayed a power-law dependence on the Reynolds number. The CFD simulation demonstrates that the body of Saccharum contortum seeds possesses a streamlined shape, with frictional forces within the boundary layer dominating drag during free fall and upward wind conditions. The presence of hairs leads to an increase in pressure drag, suggesting the formation and influence of eddy motions in the wake of seeds. See our publication here.