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A simplified stochastic model of coherent structures for particle deposdition in turbulent boundary layers
Lookup NU author(s)
Dr Ian Potts
Emeritus Professor Mike Reeks
Jin C, Potts I, Reeks MW
Conference Proceedings (inc. Abstract)
7th International Conference on Multiphase Flow (ICMF 2010)
Tampa, Florida, USA
Year of Conference
30 May - 4 June 2010
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In this paper, we deal with inertial particle deposition in a fully developed turbulent boundary layer using a stochastic Lagrangian particle tracking method. The stochastic Lagrangian model was inspired by the quadrant analysis first proposed by Willmarth & Lu (1972). The coherent structures, such as sweeps and ejections, in the inhomogeneous turbulent boundary layer seen by particles are simulated through categorized normal velocity fluctuations and relative frequency in the four quadrants, which were obtained through Large Eddy Simulation using FLUENT v6.3.26. The corresponding data agree well with the quadrant analysis ofWei &Willmarth (1991) and Willmarth & Lu (1972). This simplified stochastic model based on the physical features of the turbulent boundary layer is simpler than the previous similar model accounting for sweeps and ejections proposed by Guingo&Minier (2008). The results for dimensionless particle deposition velocity compare favorably with the experimental measurements of Liu & Agarwal (1974), in particular for large particles, as shown in Figure 1, but they under-predict deposition for small particles. However, the under-predicted dimensionless particle deposition curve is in good agreement with Guingo & Minier (2008). In both cases the under-prediction may be due to over estimation of the efficiency of ejections in removing particles from the region near the wall to the outer flow. Marchioli & Soldati (2002) have described physical mechanisms which may cause the efficiency of ejections in removing particles from the wall to be less than that of sweeps causing particles to migrate to the wall. This issue will be investigated further.
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v-velocity fluctuations in a turbulent channel flow in the context of sediment transport, Journal of Fluid Mechanics, Vol.
223, pp. 241-252, 1991 Guingo M. and Minier J. P., A stochastic model of coherent structures for particle deposition in turbulent flows, Physics of Fluids, Vol. 20, pp. 053303-053317, 2008 Liu B. Y. H. and Agarwal J. K., Experimental observation of aerosol deposition in turbulent flow, Journal of Aerosol Science, Vol. 5, pp. 145-155, 1974 Marchioli C. and Soldati A., Mechanisms for particle transfer and segregation in a turbulent boundary layer, Journal of Fluid Mechanics, Vol. 468, pp. 283-315, 2002
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