Coherent structures and the distribution of age
The transformation, growth and decay of chemical and biological species in environmental flows depend on the time history of these species within a fluid body. For example, the water quality in a lake depends on the residence time distribution (RTD) and path of each water parcel as it passes through the lake. However, most current laboratory fluid mechanical measurement techniques return Eulerian velocity and species concentration fields, which can only be used indirectly to infer residence time. We are developing a new technique that directly resolves the residence time field in laboratory experiments and is well-suited to linking fluid dynamics to environmental and ecological applications.
The video above shows the age field in a river plume experiment using the new technique on our rotating table. The colors correspond to the fluid age, normalized by the table rotation period (equivalent to days). The experiment was carried out by Melyssa Nagamine, an undergraduate working with our research group.
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