| Particulate matter is common in nature and engineering applications.When the airflow with fine particles flew through a wall,the particles will be deposited due to factors such as the turbulent structure near the wall,the interaction between the particles and the wall,and the wall material.Due to the processing problem,there is no absolutely smooth surface in engineering practice.In this paper,the rough wall surface was simplified by arranging the transverse rib structure on the surface.The presence of the rough structure disturbed the flow field near the surface,generated a series of turbulent eddies,and changed the flow field which made the flow field more complicated.Moreover,the particle-to-particle,particle-to-wall collision,rebound,and particles agglomeration behavior make the particle deposition process unclear.Therefore,it is necessary to study on particles deposition behavior on the rough surface in-depth.In this paper,the CFD(Computational Fluid Dynamics)—DEM(Discrete Element Method)coupled method was used to study the deposition behavior of monodisperse particles and polydisperse particles on rough surface,take the collision,rebound and adhesion between particles into consideration.The influence of the inlet air velocity on particle deposition characteristics reveals the particle deposition mechanism from the particle motion trajectory,collision force,adhesion force,coupling force and collision angle.And the simulation results and the experimental data were compared and verified.The simulation results of the monodisperse particles deposition characteristics on the rough surface showed that:In the vortex diffusion collision area,due to the interception of the rough structure,the turbulent vortex entrainment and the adhesion between particle and rough surface,the dimensionless deposition velocity of the small particles(10-1<?p+<10)on the rough surface was significantly higher than that of the smooth surface;For larger particles(?p+>10),the particle-rough surface collision,rebounds,and the vortex is not enough to entrain the particles to deposit,resulting in the particle deposition velocity of the rough surface was smaller than that of the smooth surface.Due to adhesion,agglomeration occurs between the particles and forms the chain structure,and the chain structure is more obvious when the particles were larger.When the particles diameter were between 10 ?m and 50 ?m,the adhesion is about 100 times that of 2 ?m particles,so the particle-to-particle adhesion had a certain effect on the dimensionless deposition velocity of large particles.For the particles of 10 ?m,30 ?m and 50 ?m,the dimensionless deposition velocity of the particles decreases first and then stabilizes with the increase of the collision recovery coefficient,the overall change velocity of the 2 ?m particles deposition velocity of is very small.The simulation results of the polydisperse particles deposition characteristics on the rough surface showed that:When the air velocity is changed,the thickness of the boundary layer is not the significant factor that caused the particle deposition to change.Near the two rough structures at the entrance of the channel,the particle deposition probability density is almost not affected by the particle mass concentration,starting from the third rough structure,the particle deposition probability density reaches a maximum at a mass concentration of 2.78 g/m3.As the air velocity increased,the non-dimensional particles deposition velocity decreased,and the decrease is larger and larger.This was because the coupling force of the fluid to the particles increases when the air velocity increased.The coupling force at 8 m/s air velocity is 2.3 times that of 4 m/s,resulting in an increase in the collision force between the particles and the surface,and the rebound angle after the collision increased.For each 2 m/s increase in the air velocity,the rebound angle of the particles to the first rough structure increased by approximately 10°. |
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