Physics and modelling of turbulent particle deposition and entrainment: Review of a systematic study

Deposition and entrainment of particles in turbulent flows are crucial in a number of technological applications and environmental processes. We present a review of recent results from our previous works, which led to physical insights on these phenomena. These results were obtained from a systematic numerical study based on the accurate resolution – Direct Numerical Simulation via a pseudo-spectral approach – of the turbulent flow field, and on Lagrangian tracking of particles under different modelling assumptions. We underline the multiscale aspect of wall turbulence, which has challenged scientists to devise simple theoretical models adequate to fit experimental data, and we show that a sound rendering of wall turbulence mechanisms is required to produce a physical understanding of particle deposition and re-entrainment. This physical understanding can be implemented in more applied simulation techniques, such as Large-Eddy Simulation. Our arguments are based also on the phenomenology of coherent structures and on the examination of flow topology in connection with particle preferential distribution. Starting from these concepts, reasons why theoretical predictions may fail are examined together with the requirements which must be fulfilled by suitable predictive models.