Effect of Drag Force Modeling on the Flow of Electrostatically Charged Particles

TL;DR

This study investigates how different drag force models affect the behavior of electrostatically charged particles in CFD simulations, revealing significant impacts for uncharged particles but minor effects when particles are highly charged.

Contribution

The paper evaluates the influence of various drag force correlations on charged particle flow in CFD, highlighting the importance of wall and particle interactions for uncharged particles.

Findings

Drag force correlation significantly affects uncharged particle concentration near walls.

Electrostatic forces cause particles to accumulate closer to walls, reducing drag model sensitivity.

High charge levels diminish the impact of drag force modeling on particle distribution.

Abstract

In CFD simulations of two-phase flows, accurate drag force modeling is essential for predicting particle dynamics. However, a generally valid formulation is lacking, as all available drag force correlations have been established for specific flow situations. In particular, these correlations have not been evaluated for particle-laden flows subjected to electrostatic forces. The paper reports the effect of drag force modeling on the flow of electrically charged particles. To this end, we implemented different drag force correlations to the open-source CFD tool pafiX. Then, we performed highly-resolved Direct Numerical Simulations (DNS) using the Eulerian-Lagrangian approach of a particle-laden channel flow with the friction Reynolds number of 180. The simulations generally revealed a strong influence of the precise drag correlation on particles in the near-wall region and a minor effect on the particles far from the walls. Due to their turbophoretic drift, particles accumulate close to the channel walls. For uncharged particles, the simulations show large deviations of the particle concentration profile in the near-wall region depending on the drag force correlation. Therefore, the disturbance of the flow surrounding a particle by a nearby wall or other particles is important for its drag. Driven by electrostatic forces, charged particles accumulate even closer to the wall. Contrary to the uncharged cases, when the particles carry a high charge (in our case one femto-coulomb), we found minor effects of drag force modeling on particle concentration profiles. In conclusion, for the investigated conditions, we propose to account for the effect of nearby particles and walls on the drag of low- or uncharged particles.