| Zusammenfassung |
In manifold industries, the electric charging of powder while it is transported through pipes or ducts is a potential source of ignition and, therefore, a hazard to the operational safety of plants. For pure fluid flows, the relevance of the flow pattern for their charging has been highlighted previously. However, the modulation of particles’ trajectories by the rise of an electric field, i.e., the back-coupling of charges on the flow, has not been investigated yet. To this end, we performed large-eddy simulations to shed light on the question if electric effects modulate turbulent particle-laden flows to a significant extent. Specifically, a fully developed turbulent carrier gas of a Reynolds number of 10 000 in a generic computational domain representing a squared-shaped duct was solved. The flow was seeded by monodisperse particles at a solid-gas mass loading ratio of 0.01 to which a constant amount of charge was assigned, namely, 0 pC, 0.125 pC, or 0.25 pC. It was found that uncharged particles accumulate at the duct walls and, in particular, in its corners due to their turbophoretic drift. However, if charge of the same polarity is assigned to the particles, repelling forces arise in-between them which are especially important in regions where the average particle distance is low. These forces affect a migration in the wall-normal direction leading to a more homogeneous distribution. Furthermore, assigned charge stabilizes the particle trajectories and dampens their velocity fluctuations in most regions of the flow. These findings contribute to the understanding of the role of electrostatic forces in particle-laden flows and may facilitate the control of the flow pattern by adjusting their charge. |
