A stochastic model of coherent structures for particle deposition in turbulent flows

In this paper, we propose a new stochastic Lagrangian model that is used to compute particle deposition rate in turbulent flows. This one dimensional boundary-layer model of the velocity of the flow seen by a particle explicitly simulates the interaction of particles with the near-wall coherent phenomena governing the wall-normal transport of particles (the so-called sweep and ejections events). For this purpose, a Markovian jump process, driving other stochastic processes, is introduced to model the coherent events. This method is believed to be one of the first attempts to include relevant geometrical features of the near-wall region in a statistical Lagrangian description. The model is first validated by comparing results obtained in the fluid-particle limit to available statistics of the boundary layer and by ensuring that the well-mixed condition is satisfied. Then, the deposition velocity is computed, and good agreement with experimental data is obtained. Furthermore, the two deposition regimes (“free flight” and “diffusional”) recently identified by direct numerical simulations are qualitatively retrieved.