Collaborative Research: Correlating Large-Scale Visual Structures to Entrainment Mechanisms in Buoyant and Momentum-Driven Plumes

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This research will explore the development of buoyant plumes, specifically to quantify how physical structures that develop along the plume/ambient interface result from mass transport through an outlet, and how these structures subsequently affect entrainment and mixing. This work will uncover mechanistic differences in plume evolution, depending on source conditions, thus informing transport models to appropriately incorporate physics for these phenomena. This is key to understanding and predicting the fate of nutrients or pollutants from plumes – for example, volcanic ash clouds, discharges into bays or estuaries, and a host of other environmental and industrial flows. While the fluid dynamics community has long acknowledged the range of physical length scales of eddies in turbulent flows, there exists a lack of research regarding how the exterior structure of a plume or jet is linked to the source conditions. Knowledge uncovered through this research will provide robust means for quantifying plume dynamics through image analysis of remotely acquired data. The research will support the training of two graduate students and undergraduate researchers. The research team will develop workshops for local outreach and educational programs, and data from the outreach events will be used in the research mission. Finally, this project will form the basis for a project for a graduate student in the WHOI summer program in Geophysical Fluid Dynamics.Laboratory experiments and direct numerical simulations will be conducted to satisfy two primary objectives. The first goal is to develop techniques to identify and quantify features comprising the plume structure to remotely determine source conditions of industrial or natural plumes from video or photographic recordings. The second goal is to investigate mechanisms of mixing and entrainment at the plume/ambient interface. In laboratory experiments, simultaneous spatio-temporally resolved particle image velocimetry and laser induced fluorescence measurements will be used to quantify the flow field and mass transport, respectively. Time lapse stereo photogrammetry will be used to reconstruct the dynamic three-dimensional outer edge of the plume, from which distributions of the length scales comprising the external structure can be characterized. A complementary suite of direct numerical simulations will be performed in quiescent unstratified and stratified background fluids. The turbulent/non-turbulent interface and the structures driving entrainment and mixing at the plume edges will be identified in the simulation data and subsequently be compared to the laboratory data. This research will enhance our ability to determine source conditions during plume-driven phenomena, including but not limited to volcanic eruptions, forest fires, glacial discharge plumes, undersea dispersion, and disease transmission.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.