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Break-up of aerosol agglomerates in highly turbulent gas flow

Lookup NU author(s): Dr Yasmine Ammar, Emeritus Professor Mike Reeks

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Abstract

Agglomerate aerosols in a turbulent flow may be subjected to very high turbulent shear rates which through the generation of lift and drag can overcome the adhesive forces binding the constituents of an agglomerate together and cause it to break-up. Based on the analysis of experimental measurements of breakup of agglomerates of characteristic size in the range 0.1 to 10 µm, carried by a turbulent pipe flow followed by an expansion zone with a Reynolds numbers in the range 105 to 107, this paper shows that even in wall bounded turbulence, the high turbulent shear stresses associated with the small scales of turbulence in the core can be the main source of breakup preceding any break-up that may occur by impaction at the wall. More importantly from these results, a computationally fast and efficient solution is obtained for the General Dynamic Equation (GDE) for agglomerate transport and breakup in highly turbulent flow. The evolution of the aerosol size distribution is consistent with the experimental results. This analysis shows that in the turbulent pipe flow section, the agglomerates are exposed continuously to turbulent shear stresses and experience more longer term breakup than in the expansion zone (following the pipe flow) where the exposure time is much less and break-up occurs instantaneously under to the action of very high local turbulent shear stresses. The validity of certain approximations made in the model is considered. In particular, the inertia of the agglomerates characterised by a Stokes Number from 0.001 for the smallest particles up to 10 for 10 µm


Publication metadata

Author(s): Ammar Y, Dehbi A, Reeks MW

Publication type: Article

Journal: Flow, Turbulence and Combustion

Year: 2012

Volume: 89

Issue: 3

Pages: 465-489

Print publication date: 30/05/2012

ISSN (print): 1386-6184

ISSN (electronic): 1573-1987

Publisher: Springer

URL: http://dx.doi.org/10.1007/s10494-012-9398-8

DOI: 10.1007/s10494-012-9398-8


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