Particle removal from solid surfaces via an impinging gas jet pulse: Comparison between experimental and CFD-DEM modeling results

Computational and experimental studies are performed to investigate the influence of a gas jet pulse impinging perpendicularly onto a flat solid surface seeded with a monolayer of spherical particles. A numerical resuspension model is derived to predict particle release into the gas phase during jet impingement. To this end, discrete particles are immersed in a continuous gas phase modeled via Large Eddy Simulation to capture the effect of jet turbulence on the particle detachment process. Two-way coupling between particulate and gas phase is established via a near-wall particle drag model and a lift model. Direct particle-wall interactions are captured with adhesion, rolling friction and sliding friction models. To validate the overall modeling approach, numerical results are compared with resuspension experiments for monodisperse polystyrene particles placed on a glass slide. Simulations show that the particles preferentially mobilize by rolling, followed to a limited extend by lift off from the solid surface driven by aerodynamic forces and particle-particle collisions. Resuspension occurs in the first instants after jet impingement. Computational and experimental results for removal efficiency Gamma are in good agreement in terms of the location of their r(50) parameter, i.e., the radial position where 50% of the particles have been removed by the jet; both results show a linear dependence between the r(50) value and the jet Reynolds number of the impinging jet. However, experimental Gamma(r) curves generally have a smooth sigmoidal shape whereas numerical results predict a sharp transition. Some model shortcomings are identified which lead to an underprediction of particle lift-off and which explain the observed differences. Furthermore, the experimental Gamma curves nearly collapse onto each other when plotted over the predicted local wall-shear stress.