WALL DEPOSITION OF SMALL ELLIPSOIDS FROM TURBULENT AIR FLOWS__A BROWNIAN DYNAMICS SIMULATION

Brownian dynamics simulations of the motions of ellipsoidal particles in the turbulence near-wall coherent vortices are carried out. The kinematics and the dynamics of an ellipsoidal particle moving in shear flows are outlined. Eulerʹs four parameters (quaternions) are used for describing the particle orientation. The particle equation of motion includes the hydrodynamic forces and torques, the shear-induced lift force, and the Brownian forces and torques. The near-wall coherent structures are simulated using vortical flow models. A turbulence mean flow is used in the streamwise direction, and the spanwise direction is assumed to be periodic. The wall is modeled as an absorbing (a sticky surface) boundary condition. Ensembles of particle trajectories are evaluated and statistically analyzed. For various particle sizes, aspect ratios, and densities, the deposition velocities of elongated particles in turbulent air streams are evaluated. An empirical equation for the turbulent deposition rate of ellipsoidal particles is also developed. The results are compared with earlier studies and the available experimental data.