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Nonspherical particles in turbulence and the locomotion of meso-scale aquatic organisms

February 29, 2016

  • Dr. Margaret L. Byron
  • University of California Irvine
  • Surge 117 A
  • 4:00 p.m.
  • Faculty Host: Dr. Paterson

Abstract: Interactions between suspended particles and turbulent fluid flow are everywhere in the natural and built environment, from sandy ocean floors to smoggy city skies. However, the complexity of these interactions is scale-dependent: very small particles behave as passive tracers, and very large particles may pass through turbulent eddies without being affected by them. For particles or organisms at intermediate scales, the spatiotemporal heterogeneity of the ambient flow translates to buffeting, fluctuating forces that are markedly different than those experienced by the very small or very large.  This in turn affects things like transport, settling, aggregation, and preferential concentration (in particles) and swimming, feeding, and reproduction (in aquatic organisms).

This talk will present recent experimental measurements of intermediate-size, non-spherical, near-neutrally-buoyant particles which are suspended in homogeneous isotropic turbulence. Using novel techniques in refractive-index matching, we obtain simultaneous measurements of suspended particles and the surrounding flowfield, allowing us to directly measure particles’ slip velocity and rotation and see how they are inherited from the ambient turbulence.  We will discuss how particles of this size, shape, and density can serve as models for large aggregates, small underwater vehicles, or the larger plankton. Lastly, we will outline current work on the locomotion of comb jellyfish (Earth’s largest ciliates) which employ unique propulsive strategies within this intermediate size range

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