Brown University School of Engineering

Fluids at Brown, Division of Applied Mathematics Fluids and Thermal Sciences, School of Engineering Joint Seminar Series

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Tuesday, October 17, 2017 3:00pm - 4:00pm
Barus and Holley, Room 190

Francesca Bernardi, Ph.D. Candidate Department of Mathematics University of North Carolina at Chapel Hill Symmetry-breaking in passive scalars advected by laminar shear flow Abstract: The dispersion of passive tracers in laminar shear flow is a classic problem in fluid dynamics. The boost in the tracer dispersion due to the interplay between advection and diffusion was first described mathematically and observed experimentally by Sir G. I. Taylor in 1953 for laminar flow in a straight circular pipe. This effective diffusivity sets in after the typical diffusive timescale and as such it is considered a long-time asymptotic result. This talk focuses on what happens at short and intermediate timescales for rectangular and elliptical pipes, before the effect of Taylor Dispersion is observed. In particular, at these timescales the tracer distribution is strongly asymmetric and understanding how its behavior relates to the cross-sectional geometry of the pipe is largely unexplored. Through analysis, simulation, and experiment, we explore the role different geometries play in controlling emerging longitudinal asymmetries in the cross-sectionally averaged distribution. Our results highlight the significance of the aspect ratio of the channel in controlling asymmetries and have potential implications for the design of fluidic channels in microfluidic devices. Ongoing and future directions will be discussed.