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Separated rows structure of vortex streets behind triangular objects

Published online by Cambridge University Press:  10 January 2019

Ildoo Kim Open the ORCID record for Ildoo Kim [Opens in a new window]
Ildoo Kim*
Affiliation:
School of Engineering, Brown University, Providence, RI 02912, USA
*
†Email address for correspondence: [email protected]
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Abstract

We discuss two distinct spatial structures of vortex streets. The ‘conventional mushroom’ structure is commonly discussed in many experimental studies, and the exotic ‘separated rows’ structure is characterized by a thin layer of irrotational fluid between two rows of vortices. In a two-dimensional soap film channel, we generate the exotic vortex arrangement by using triangular objects. This setting allows us to vary the thickness of boundary layers and their separation distance independently. We find that the separated rows structure appears only when the boundary layer is thinner than 40 % of the separation distance. We also discuss two physical mechanisms of the breakdown of vortex structures. The conventional mushroom structure decays due to the mixing, and the separated rows structure decays because its arrangement is hydrodynamically unstable.

JFM classification

Vortex Flows: Vortex breakdown Vortex Flows: Vortex instability Vortex Flows: Vortex shedding
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 862 , 10 March 2019 , pp. 216 - 226
Copyright
© 2019 Cambridge University Press 

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