The Nepf Lab, May 2014 (Left to right) Brenda Pepe, Ad. Ass't., Beihan Jiang, Judy Yang, Julia Hopkins,
Johannes Gerson Janzen, John Kondziolka, Elizabeth Follett, Erin Grace Connor, Heidi Nepf
Donald and Martha Harleman Professor
Civil and Environmental Engineering
Email: hmnepf (at) mit.edu
Heidi Nepf's Civil and Environmental Engineering webpage Professor Nepf's teaching includes Physical Limnology and Transport Processes in the Environment.
Elizabeth Follett Graduate Student (Email: efinn (at) mit.edu)
By forecasting the spread of fungal spores, we can reduce the amount of fungicide applied each year to crops such as corn, wheat, and soybeans. My research focuses on developing an understanding of the processes governing spore escape from a crop canopy, so that we can refine existing estimates of the probability of spore escape. Using a rigid model crop canopy, I study the impact of canopy scale vortices on particle transport using a combination of flow visualization techniques and measurements of deposition following an experimental particle release. I have also developed a simple random walk particle tracking model to explore particle escape across a wide range of canopy densities and ratios of spore settling velocity to canopy turbulence.
My research is focused on the effect of vegetation patches on turbulence generation and sediment deposition. I use a laboratory flume to simulate a fluvial environment and try to understand how patches of vegetation can change overall flow dynamics and sedimentation spatially. I am interested in how different types of vegetation affect flow dynamics and sediment distribution. So if you have a flexible plant, versus a rigid plant, does it change where sediment will build up. The retention or erosion of sediment preferentially from different areas around and within a patch of vegetation can influence different aspects of the river's ecosystem and physical characteristics.
Qingjun "Judy" Yang
Graduate Student (Email: qjyang (at) mit.edu)
My current research is focused on the sediment transport inside a vegetation patch. Vegetation is a basic component of most natural water environments and has been widely used in river restoration. Yet few practical models exist to predict the incipient motion and rate of sediment transport in a canopy. Using a LDV, a high-speed camera and a sediment-recirculating flume, I will be able to quantitatively connect the sediment motion with the flow characteristics inside vegetation canopies.
Beihan Jiang Graduate Student(Email: jbeihan (at) mit.edu) The mutual influences between biological and physical processes, called biogeomorphic feedbacks, play a key role in the landscape evolution. I am currently studying the feedback between patches of
vegetation, flow, and deposition in connection to the geomorphologic evolution of rivers and tidal flats. In particular, I am examining how neighboring patches of vegetation alter the flow field and promote deposition and growth into larger vegetation structures. The initial vegetation is modeled as a pair of adjacent patches, constructed from rigid circular cylinders. The wakes of the patches create conditions for deposition that favor patch expansion in the downstream direction. In addition, the merger of wakes from the individual patches creates regions of low velocity on the centerline between the patches that promotes eventual merger of the two original patches. We recreate the cycle of deposition-growth-flow adjustment by progressively applying artificial vegetation growth in regions of enhanced deposition. The goals are to provide new insight into the feedbacks between vegetation, flow and morphologic evolution, and to understand how vegetation adapts to and develops in different fluid environments.
Graduate Student (Email: garylei (at) mit.edu)
My project aims to understand how the rate of nutrient flux to the plant changes with the motion and posture of individual blades. The impacts of neighboring blades on nutrient flux will also be examined. I will work with both meadow and model blades which are constructed from low-density polyethylene (LDPE). The LDPE blade can absorb chemicals injected in the flume water, to simulate the nutrient-uptake of sea grass and freshwater macrophytes. This project will extend existing models for drag /flux to individual blades in current, and also explore a predictive model for mass flux based on different flow conditions.