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Clustering of gyrotactic microorganisms in turbulent flows

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We study the spatial distribution of gyrotactic microorganisms swimming in a three-dimensional turbulent flow by means of direct numerical simulations. We find that gyrotaxis combines with turbulent fluctuations to produce small scales patchiness with fractal clustering. We explain our observations by showing that gyrotactic swimming cells behave like tracers transported by an effective compressible flow. We derive an explicit expression for the compressibility in the limit of fluid acceleration much smaller than gravity.

Author(s):

Guido Boffetta    
University of Torino
Italy

Michael Barry    
Massachusetts Institute of Technology
United States

Massimo Cencini    
ISC-CNR
Italy

Eric Climent    
University of Toulouse
France

Filippo De Lillo    
University of Torino
Italy

William Durham    
University of Oxford
United Kingdom

Roman Stocker    
Massachusetts Institute of Technology
United States