Modulation of turbulence by dispersed charged particles in pipe flow

Abstract

Turbulent gas–solid two-phase flow with electrostatic effects is studied. The turbulent pipe flow is treated using large-eddy simulation, while the particles are tracked using a Lagrangian approach. Simulations are carried out with one-way coupling, two-way coupling, and two-way coupling taking account of electrostatics, and the results are compared. The bulk Reynolds number is Reb = 44 000, and the Stokes number is St = 3.9 (dp = 5 μm). The results show that the maximum electrostatic field strength in the saturated state is found near, but not at, the wall. The electrostatic effect increases the particle concentration in the viscous sublayer (0 ≤ y+ ≤ 5) and the particle dispersion in the buffer layer (5 ≤ y+ ≤ 30). Owing to the electrostatic effect, the feedback effect of particles on the fluid is increased, which leads to increase in the average fluid velocity in the buffer layer and in the velocity fluctuations. In addition, the electrostatic effect is found to increase the turbulent kinetic energy near the wall, while this trend decreases with distance away from the wall. The areas of high- and low-speed streaks near the wall are increased by the electrostatic effect. Therefore, it can be concluded that electrostatics changes not only the particle behavior, but also the flow field.