Numerical Simulation of Aerosol Particle Deposition in an Impinging Jet

Eid Alatawi (1), Edgar Matida (2)

(1) Carleton University, (2) Carleton University

     Abstract Number: 374
     Last modified: May 11, 2010

Abstract
The flow of a turbulent jet laden with particles and impinging vertically onto a surface has several applications ranging from sand blasting, inkjet printing, surface erosion, cascade impactors, and pharmaceutical aerosols. Aiming at the better understanding of the physics behind impinging jet effects from inhaler devices, the deposition of 5 micro-meter particles over the impingement wall is predicted for three cases of nozzle-to-surface distances, L, i.e., L/D = 2, 4 and 6, where D is the diameter of the nozzle (15 mm). The continuous phase flow was solved using Reynolds Averaged Navier Stokes (RANS) along with the shear stress transport (SST) turbulence model (CFX 12.0, Ansys, Inc.). The particulate phase was simulated using a Lagrangian random-walk eddy-interaction model (EIM), where the trajectories of individual particles are tracked in the computational domain by solving the particle equation of motion. 3D structured multi-block meshes of 0.75x10$^6, 1.5x10$^6 and 2.25x10$^6 nodes were used in the modeling of the L/D=2, 4 and 6 cases, respectively. A constant velocity profile for the inlet condition is assumed. The Reynolds number based on the inlet nozzle diameter is 10,000 with u = 10.5 m/s. A constant zero gauge pressure was applied at the outlet opening of the computational domain. The particles were modelled to be solid and one–way coupling was used to govern the particle-fluid interaction. By considering particles with higher densities than the fluid, the particle equation of motion is reduced to account only the viscous drag force. The deposition patterns using the turbulent dispersion (with a random- walk EIM model using different levels of correction by different eddy viscosity ratios) and mean flow tracking (no modelling) were predicted. The results showed that the deposition of the particles exhibits a ring-like pattern similar to separate experimental data when the turbulent tracking was used. This pattern was absent and few particles were deposited on the wall when the mean flow tracking was used, as expected.