Berkeley Fluids Seminar

University of California, Berkeley

Bring your lunch and enjoy learning about fluids!

Monday, April 9, 2018

12:00-13:00, 3110 Etcheverry Hall

Dr. Alexandra T. King (Cornell University)

A k-epsilon model for flow through aquatic vegetation

Abstract: Flow and transport through aquatic vegetation is characterized by a wide range of length scales including water depth (H), stem diameter (d), the inverse of the plant frontal area per unit volume (af), and the scale(s) over which af varies (the most easily identified is the plant height, h). Turbulence is generated both at the scale(s) of the mean vertical shear, set by the inverse of af, and at the scale(s) of the stem wakes, set by d. While turbulence from each of these sources is dissipated through the energy cascade, some shear-scale turbulence bypasses the lower wave numbers as shear-scale eddies do work against the form drag of the plant stems, converting shear-scale turbulence into wake-scale turbulence. We have developed a k-epsilon model that accounts for all of these energy pathways. The model is calibrated against laboratory data from beds of rigid cylinders under emergent and submerged conditions. The new model outperforms existing models, none of which include the d scale, both in the emergent case, where existing models break down entirely, and in the submerged case, where existing models fail to predict the strong dependence of turbulent kinetic energy on d. The success of the new model supports our current understanding of the turbulent kinetic energy budget in flow through vegetation. The new model was developed with applications in real aquatic vegetation in mind, and may be easily incorporated into larger hydrodynamic solvers for field applications.

Bio: Allie King has a B.S. in Civil Engineering from Rice University and M.S./Ph.D. degrees in Civil & Environmental Engineering from Cornell University. As a doctoral student, Allie developed a new RANS model for flow through aquatic vegetation, which she will talk about today. As a Postdoc in the same department, Allie worked on coupling near-field dynamics of cooling water outfalls to three-dimensional hydrodynamic models. As a Research Associate in Cornell's Department of Ecology & Evolutionary Biology, Allie is working to understanding the role of internal waves in delivery of Phosphorus to cyanobacteria.

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