Investigation of granular dispersion in turbulent pipe flows with electrostatic effect

The electrostatic effect on granular dispersion in circular pipe flows at Reb = 44,000 was investigated using Large Eddy Simulation (LES) in one-way coupling Lagrangian granule tracking method. Granule motion equation is governed by drag force, gravity and electrostatic force. LES results obtained for single phase flow agree well with experimental data and DNS results. Three granule sizes (dp = 20, 80, 200 μm) were considered in this work. It is found that in the absence of electrostatic effect granular dispersion near the wall mainly depends on local flow characteristics. Electrostatic effect was found to change the effect of turbulent flows on granular dispersion particularly near the pipe wall. Granules were found to accumulate in the near-wall region (y/R > 0.95) but well distribute in most pipe (0 < y/R < 0.95). In the near-wall region, it is electrostatic force that dominates granular concentration, which is independent of granule size. In addition, the electrostatic force is found to be obviously larger than drag force and gravity for all sized granules in this region. In most pipe region (y/R < 0.95) electrostatic effect tends to decrease granular concentration and it becomes more significant with granule size. © 2020 Society of Powder Technology Japan