直方槽道内两相流动中颗粒的趋壁行为

采用大涡模拟方法研究了上行直方槽道中的气粒两相流动过程,模拟结果表明在流向横截面上气相流动存在明显的二次流现象,预报的气相平均速度与直接数值模拟DNS的结果相吻合。受气相二次流的作用,颗粒在垂直于流动方向存在扩散。模拟了入口横截面上4个典型位置上颗粒的横向扩散,结果表明在直方槽道中心附近的颗粒基本不扩散,而在壁面附近的颗粒存在不同程度的趋壁行为。对颗粒的趋壁速率进行统计发现颗粒的趋壁速率随粒径的增大而减小,且颗粒的趋壁行为导致颗粒在槽道壁面附近及边角区富集。

Particle flow towards the wall in gas-particle flows through a square duct

Co-current upwards gas-particle flow in a square duct was studied using large-eddy simulations. The simulations predicted turbulence driven secondary flow in square duct cross section. The predicted statistically averaged gas velocities also agreed well with direct numerical simulation data. The secondary gas flow dispersed the particles in the lateral direction. Lateral dispersion of particles into four representative regions at the entrance of the square duct was investigated. The results show that particles in the center of the square duct undergo little dispersion. However, particles near the walls tended to move towards the nearest wall. The averaged velocity towards the wall increased as the particle diameter decreased. As a result of this flow towards the walls, the particles tend to concentrate near the walls and the corners.