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Details

Autor(en) / Beteiligte
Titel
Particle resuspension in turbulent boundary layers and the influence of non-Gaussian removal forces
Ist Teil von
  • Journal of aerosol science, 2013-04, Vol.58, p.103-128
Ort / Verlag
Oxford: Elsevier Ltd
Erscheinungsjahr
2013
Link zum Volltext
Quelle
Elsevier ScienceDirect Journals Complete
Beschreibungen/Notizen
  • The work described is concerned with the way micron-size particles attached to a surface are resuspended when exposed to a turbulent flow. An improved version of the Rock’n’Roll model (Reeks & Hall, 2001) is developed where this model employs a stochastic approach to resuspension involving the rocking and rolling of a particle about surface asperities arising from the moments of the fluctuating drag forces acting on the particle close to the surface. In this work, the model is improved by using values of both the streamwise fluid velocity and acceleration close to the wall obtained from Direct Numerical Simulation (DNS) of turbulent channel flow. Using analysis and numerical calculations of the drag force on a sphere near a wall in shear flow (O’Neill, 1968; Lee & Balachandar, 2010) these values are used to obtain the joint distribution of the moments of the fluctuating drag force f(t) and its derivative ḟ(t) acting on a particle attached to a surface. In so doing the influence of highly non-Gaussian forces (associated with the sweeping and ejection events in a turbulent boundary layer) on short and long term resuspension rates is examined for a sparse monolayer coverage of particles, along with the dependence of the resuspension upon the timescale of the particle motion attached to the surface, the ratio of the rms/mean of the removal force and the distribution of adhesive forces. Model predictions of the fraction resuspended are compared with experimental results. ► R’n’R model is improved by including the statistics of the fluctuating aerodynamic resultant force and its derivative. ► Distribution of these statistics normalised on their rms is highly non-Gaussian and independent of y+ in the viscous sublayer. ► Typical burst frequency ω+ is the crucial in short term resuspension and the rms coefficient frms is the key parameter for long-term. ► We have examined the implications for resuspension of using two different formula for drag force.

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