Numerical simulations of aggregate breakup in bounded and unbounded turbulent flows

Breakup of small aggregates in fully developed turbulence is studied by means of direct numerical simulations in a series of typical bounded and unbounded flow configurations, such as a turbulent channel flow, a developing boundary layer and homogeneous isotropic turbulence. The simplest criterion f...

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Bibliographic Details
Published in:Journal of fluid mechanics 2015-03, Vol.766, p.104-128
Main Authors: Babler, Matthaus U., Biferale, Luca, Brandt, Luca, Feudel, Ulrike, Guseva, Ksenia, Lanotte, Alessandra S., Marchioli, Cristian, Picano, Francesco, Sardina, Gaetano, Soldati, Alfredo, Toschi, Federico
Format: Article
Language:English
Subjects:
Aggregates
Boundary layers
Breakup
breakup/coalescence
Channel flow
Computational fluid dynamics
Computer simulation
Configurations
Energy dissipation
Energy exchange
Fluids
Hydrodynamics
Inhomogeneity
Isotropic turbulence
multiphase and particle-laden flows
Physics
Scaling
Studies
Thresholds
Turbulence
Turbulent flow
turbulent flows
Variation
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Summary:Breakup of small aggregates in fully developed turbulence is studied by means of direct numerical simulations in a series of typical bounded and unbounded flow configurations, such as a turbulent channel flow, a developing boundary layer and homogeneous isotropic turbulence. The simplest criterion for breakup is adopted, whereby aggregate breakup occurs when the local hydrodynamic stress ${\it\sigma}\sim {\it\varepsilon}^{1/2}$ , with ${\it\varepsilon}$ being the energy dissipation at the position of the aggregate, overcomes a given threshold ${\it\sigma}_{cr}$ , which is characteristic for a given type of aggregate. Results show that the breakup rate decreases with increasing threshold. For small thresholds, it develops a scaling behaviour among the different flows. For high thresholds, the breakup rates show strong differences between the different flow configurations, highlighting the importance of non-universal mean-flow properties. To further assess the effects of flow inhomogeneity and turbulent fluctuations, the results are compared with those obtained in a smooth stochastic flow. Furthermore, we discuss the limitations and applicability of a set of independent proxies.
ISSN:0022-1120
1469-7645
1469-7645
DOI:10.1017/jfm.2015.13