Email: ytanino @ mit.edu
Web page
I am currently investigating the effect of rigid, emergent vegetation on lateral mixing, focusing on slower flows (stem Reynolds numbers of 200 or less) through dense vegetation. In a laboratory flume, fluorescent dye is released within a model canopy and the lateral concentration profile is measured at different distances downstream. The lateral diffusivity is then calculated from these profiles and compared with theoretical predictions.
My next project will examine the hydrodynamic effects of rigid aquatic vegetation on convective currents, which are flows driven by spatial gradients in density. The goal is to develop a predictive model for the horizontal velocity and the vertical structure of gravity currents.
Email: xyzhang @ mit.edu
I am studying the exchange flow in a water body driven by spatial heterogeneity of water temperature. The presence of emergent or submerged vegetation may shelter the water and reduce the incident solar radiation. Spatial temperature gradient may arise from the difference in energy absorption, and these gradient drive lateral exchange flows. In addition, the vegetation provides significant drag that may reduce the magnitude of resulting exchange flows. The objective of the project is, by means of experiments and modeling, to evaluate the impacts of vegetation on the thermally-driven exchange flows.
Email: mluhar @ mit.edu
I am studying the hydrodynamic impact of submerged seagrass meadows, an important component of coastal ecosystems. In addition to providing habitat for a variety of fauna, seagrass meadows have a significant impact on the fate and transport of nutrients and contaminants. Physical processes, such as mass exchange between the seagrass canopy and the overlying open water (i.e. water renewal), are often important factors regulating biogeochemical cycles in these environments. Through laboratory experiments and physically intuitive analytical models, I aim to quantify mass and momentum exchange rates between submerged seagrass meadows and the overlying open water for varying seagrass blade densities in different flow conditions involving waves and unidirectional currents. Eventually, I also hope to study an interesting, related hydrodynamic problem: the wave damping effects of the high-drag, submerged seagrass canopies.
Email: jtr @ mit.edu
I am investigating the interaction between currents and patch-scale aquatic vegetation. Patches of vegetation occur naturally in rivers, lakes and coastal zones and are of vital importance to the overall ecosystem. The effectiveness of this vegetation at controlling sedimentation, removing nutrients from the water, and providing a habitat for microorganisms often depends on how water moves through the vegetation, and therefore how long the water is in contact with the vegetation. Currently, the hydrodynamics associated with this patch-scale vegetation are not well understood. I am using acoustic doppler velocimetry (ADV), and laser doppler anemometry (LDA) to understand how water moves through and around these regions. These laboratory experiments will enable me to describe hydrologic retention times for different flow regimes. Field studies on different types of vegetation will be used to confirm the laboratory models. These results will be useful for river engineers, biologists and many other researchers interested in the fluid mechanics of aquatic ecosystems.
Current Position: Assistant Professor of Marine Sciences
University of North Carolina at Chapel Hill
Email: bwhite @ unc.edu
I worked on flow in channels partially filled with vegetation, typical of those in river-floodplain systems, mangroves, and salt marshes. These are interesting because, due to the drag discontinuity between the vegetation and the main channel, a shear layer develops across the vegetation interface, giving rise to an instability that forms coherent vortices. The coherent structures induce strong, periodic fluctuations in the velocity, and dominate momentum and scalar fluxes across the interface. In natural systems, these structures likely contribute to significant transport of biological and chemical material between stands of vegetation and the main channel.
Current Position: Assistant Professor of Marine Sciences
St. Anthony Falls Laboratory
I explored the effect of transverse deep zones on the hydraulic performance of constructed wetlands that contain short-circuiting channels. I used laboratory physical models to study the effect of short-circuiting channels in wetlands and the ability of transverse deep zones to correct for these inefficiencies. Techniques include particle image velocimetry (PIV) to study flow and laser-induced fluorescence (LIF) to study transport. Concurrent field work tests whether these laboratory models replicate a real-world constructed wetland. The eventual goal is to produce design criteria that could be used by designers of constructed wetlands.
Email: murphye @ alum.mit.edu
I investigated the effects of vegetation on mass transport in aquatic systems. This is a subject that is highly relevant to water quality control, channel management, wetland design, and predicting the effects of land use change. My work involves constructing tracer studies in a laboratory flume to determine dispersion coefficients for a wide range of flow regimes. This will be helpful in developing a predictive model for longitudinal dispersion in vegetated channels. The transition from deeply submerged to emergent vegetation is of particular interest, since this is a common environmental condition about which little is known. I am also working on a numerical, random walk particle-tracking model, which will give insight into mixing time scales and incorporate biological/chemical effects.