How gravity and size affect the acceleration statistics of bubbles in turbulence

ORAL

Abstract

We report results from a Lagrangian experimental investigation in the largely unexplored regime of very light (air bubbles in water) and large particles ($D / \eta >> 1$) in turbulence. Using a traversing camera setup and particle tracking, we study the acceleration statistics of $\sim 3 \ mm$ diameter ($D$) bubbles in a water tunnel with nearly homogeneous and isotropic turbulence generated by an active-grid. The experiments reveal that gravity increases the acceleration variance and reduces the intermittency of the PDF in the vertical direction. Moreover, the experimental acceleration PDF shows a substantial reduction in intermittency at growing size ratios, in contrast to neutrally buoyant or heavy particles. All these results are closely matched by numerical simulations of finite-size bubbles with Fax\'en corrections.

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Authors

  • Vivek N. Prakash

    • Physics of Fluids Group, University of Twente, The Netherlands

  • Yoshiyuki Tagawa

    • Physics of Fluids Group, University of Twente, The Netherlands

  • Enrico Calzavarini

    • Laboratoire de Mecanique de Lille CNRS/UMR, Universite Lille 1, France

  • Julian Martinez Mercado

    • Physics of Fluids Group, University of Twente, The Netherlands

  • Federico Toschi

    • Eindhoven University of Technology, The Netherlands
    • Eindhoven University of Technology
    • Department of Physics, and Department of Mathematics and Computer Science, Eindhoven University of Technology, The Netherlands

  • Detlef Lohse

    • University of Twente
    • Physics of Fluids, University of Twente, Enschede
    • Physics of Fluids, University of Twente
    • Physics of Fluids group, University of Twente, Netherlands
    • Universiteit Twente
    • University of Twente, Physics of Fluids Group
    • University of Twente, Enschede, The Netherlands
    • Physics of Fluids Group, Faculty of Science and Technology, J.M. Burgers Center for Fluid Dynamics, and IMPACT Institute, University of Twente, NL
    • Physics of Fluids Group, University of Twente, The Netherlands

  • Chao Sun

    • University of Twente
    • Physics of Fluids group, University of Twente, Netherlands
    • Universiteit Twente
    • University of Twente, Physics of Fluids Group
    • University of Twente, Enschede, The Netherlands
    • Physics of Fluids Group, University of Twente, The Netherlands