Direct Numerical Simulation Of Inhalable Particle Motion In Channel Flow

Inhalable particles can do great harm to people's health which remain the keypollutant affecting the air quality in China. Therefore, it is necessary to study themotions of inhalable particles.In the earlier numerical study of two-phase flow, the turbulent models are oftenused to simulate the turbulent flow. It is an effective way to simulate the motions ofbigger particles which turns impossible when the particles are smaller than theKolmogorov length. The direct numerical simulation (DNS) solves the N-S equationdirectly and can provide all the data of the turbulent flow. Therefore, it had beenwidely used in the simulation of micro particles.Firstly, a three dimension, incompressible, turbulent channel flow without thetemperature difference is simulated. The Lagragian method is used to track themotions of particles. The particle diameters simulated in this study are 1 μm, 2.5 μm,10 μm, 20 μm and 100 μm. The numerical results reveal that the particles tend toaccumulate in the flow. The difference among the particle concentration is discussed.Secondly, the motions of the particles with the temperature difference of 130℃and 180℃ are simulated. The comparison with the date of no temperature differenceis made. The numerical results show that the effect of thermophoresis on thedeposition near the wall decreases with increasing particle diameter and the particledeposition increases as the temperature difference increases.Finally, the particle motions with mutual collisions are simulated. The resultsshow that the particles tend to collide in the region of higher particle concentration orin the region of higher kinetic energy.