Modeling and simulation of particle–wall adhesion of aerosol particles in particle-laden turbulent flows

Abstract

© 2016 Elsevier Ltd The present study is concerned with the development of a computational model for predicting particle–wall adhesion (deposition) of aerosol particles in turbulent particle-laden flows. Particularly, the standard hard-sphere model is extended to include the adhesion during sticking or sliding particle–wall collisions. For both impact types the deposition condition of a particle on bounding walls is determined. The strategy of the proposed model is based on the momentum-based agglomeration model by Breuer and Almohammed (2015). The main advantage of the proposed model compared to the state-of-the-art in the literature is that the adhesive impulse is determined more reasonably taking the time intervals of the compression and the restitution phase into account. Furthermore, if the deposition condition is not satisfied, the treatment of the particle motion after the impact including adhesion depends on the particle–wall type (sticking or sliding). To examine the effect of the particle–wall adhesion, the developed model is first evaluated using simple test cases including oblique particle–wall collisions with friction. In the second step, the performance of the adhesion model is validated based on a horizontal turbulent channel flow against existing experimental data of Kvasnak et al. (1993) and numerical results by Fan and Ahmadi (1993)based on an energy-based deposition model. The predictions of the present model agree very well with the experiments and the numerical results chosen for the validation study as well as the empirical relation by Wood (1981). Third, the adhesion model is employed to investigate the influence of different simulation parameters (normal restitution coefficient for particle–wall collisions and particle diameter) on the particle–wall adhesion and deposition process in a vertical turbulent channel flow laden with a huge number of primary particles. The results show that the inclusion of the adhesion significantly reduces the number of particle–wall collisions, whereas the number of particle–particle collisions is only slightly reduced. Furthermore, the number of deposited particles is higher for small particles than for large particles, since the adhesive impulse is inversely proportional to the diameter of the primary particles. The proposed adhesion model is developed and tested in the context of large-eddy simulation, but it can also be applied in DNS or RANS predictions.