Veröffentlichungen und Präsentationen

In the field of industrial marking, continuous inkjet technology is based on high speed emission of ink drops. The printing quality is directly linked to the interactions of the droplets with their environment during flight time : electric field, aerodynamic perturbations, and droplet-droplet interactions. In a former paper, all these interactions were modelled in a fully coupled Lagrangian-Eulerian approach within the COMSOL Multiphysics® software. Particularly, aeraulic interactions between droplets were obtained thanks to the air flow induced by all the droplets by resolving Navier-Stokes equations. Numerical simulations were compared to experimental data, showing a good agreement in terms of flight time and macroscopic position of the droplets on the printed medium but also inaccuracies in the gap between droplets, leading to a biased forecast of the printing quality. Resolving accurately the surrounding air flow requires in fact an extremely fine mesh. This paper studies another approach to take into account the aeraulic interactions between two droplets using abacuses. First, steady air flows around a unique droplet are computed using the Laminar Flow physics interface of COMSOL Multiphysics® for multiple droplet velocities. Second, these results are combined within interpolation functions in order to get an abacus of the air velocity field around each droplet. Finally, this abacus is integrated in the Particle Tracing physics of the former model to estimate the drag force experienced by each droplet in the air flow induced by the other one, replacing the computation of Navier-Stokes equations in the surrounding air. This new approach makes it possible to forecast phenomena of aeraulic aspiration followed by bouncing of the droplets by electrostatic repulsion, allowing a better understanding of the mechanisms and the design parameters playing on the printing quality.