Particle Removal and Re-entrainment in Turbulent Flows using Direct
Numerical Simulation (DNS)
Aerosol particle removal and re-entrainment in turbulent channel flows are studied. The instantaneous
fluid velocity field is generated by the direct numerical simulation (DNS) of the Navier-Stokes equation
via a pseudospectral method. Particle removal mechanisms in turbulent channel flows are examined and
the effects of hydrodynamic forces, torques and the near-wall coherent vorticity are discussed. The particle
resuspension rates are evaluated, and the results are compared with the model of Reeks. The particle equation
of motion used includes the hydrodynamic, the Brownian, the shear-induced lift and the gravitational forces.
An ensemble of particles is used for particle resuspension and the subsequent trajectory analyses. It is found
that large size particles move away roughly perpendicular to the wall due to the action of the lift force. Small
particles, however, follow the upward flows formed by the near wall eddies in the low speed streak regions.
Thus, turbulent near wall vortical structures play an important role on small particle resuspension, while
the lift is an important factor for re-entrainment of large particles. The simulation results suggests that small
particles primarily move away from the wall in the low speed streaks, while larger particles (with are mostly
removed in the high speed streaks.
Funded by NYSTAR through Center for Advanced Materials Processing (CAMP)