  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.
