Fragmentation of small aggregates in turbulent flows

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Fragmentation of small aggregates in turbulent flows

  • Datum: 22.11.2017
  • Uhrzeit: 14:00 - 15:00
  • Vortragender: Dr. Matthäus Bäbler, Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm, Schweden
  • Ort: Max-Planck-Institut Magdeburg
  • Raum: Großer Seminarraum "Prigogine"
  • Kontakt: sek-pcg@mpi-magdeburg.mpg.de

Abstract

Fragmentation of suspended particles is in important process in many industrial and environmental applications. For example, it is the dominant mechanism in the dispersion of agglomerates and it crucially influences the particle size distribution in aggregation or flocculation processes. Also, it plays an important role in the transport of sediments in rivers and estuaries and it might be a controlling factor for the formation of microplastics in the ocean. In this seminar, I will focus on the fragmentation of small aggregates made of polymeric colloids. Such aggregates typically have small inertia such that they follow closely the fluid streamlines of the underlying flow. This prevents the aggregates from undergoing energetic collisions with solid objects, such as vessel walls, impeller blades, or other particles, leaving us with hydrodynamic stresses as the dominant fragmentation mechanism. In our work, we addressed the fragmentation of small aggregates due to hydrodynamic stress in diluted turbulent flows. Turbulence makes the problem in as far challenging as it creates strong fluctuations of the hydrodynamic stress acting on the aggregates. In a first part I will explore the role of turbulent fluctuations on the fragmentation of individual aggregates, which we studied experimentally using 3-dimenionsal particle tracking velocimetry. In a second part I will discuss the dynamics of fragmentation in turbulence studied through numerical and present a framework that allows for deriving breakup rate functions suitable to be used within population balance models.



 
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