How do You Map a Von Karman Vortex Street and How do You Use One to Generate Electricity?

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Tim Divett
Megan Griffiths


Swirling structures in calmly flowing water inspire a deep, primal sense of peace and well-being. At the same time, images of Poe’s maelstrom in turbulent oceans inspire a sense of terror.1 Throughout the duration of my PhD, modelling the flow through ocean channels full of tidal turbines, I experienced both of those feelings. The mathematical beauty in my work is involved in the equations that I use to describe the ocean flowing through a tidal channel full of turbines.  A von Karman vortex street is the repeating pattern in parallel rows of swirling eddies that form in the wake of an obstruction in flowing fluid. The beauty and terror that eddies inspire in humanity is mirrored by the blessing and curse that these cause for engineers designing tidal turbines. While the fast-flowing water provides the power to drive the turbine, the turbulent vortices in the wake of a turbine put stress on downstream turbines by bending and twisting the blade as a vortex moves past the turbine. Understanding the balance between the power in the flow that can be captured by turbines and the impact on the natural flow by building these turbines was a fundamental part of my research.

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Author Biographies

Tim Divett, Department of Physics, University of Otago.

Tim Divett is a postdoctoral fellow in the Department of Physics, University of Otago. His PhD is on computational fluid dynamics modelling of flow around arrays of tidal power turbines.

Megan Griffiths, Dunedin School of Art at Otago Polytechnic.

Megan Griffiths graduated from the Dunedin School of Art in 2016 with an Honours degree in visual arts (textiles). Now in 2018 she has returned to the Dunedin School of Art to start work on her Master of Fine Arts. Megan has been working with textiles for more than 30 years.