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Investigation on viscous droplet generation for selective coating processes

: Ye, Qiaoyan; Rhein, Sebastian; Hess, Thomas; Niemeier, Wolfgang; Tiedje, Oliver

Univ. Sao Paulo; Universidade Federal do Rio de Janeiro:
10th International Conference on Multiphase Flow, ICMF 2019 : May 19 - 24, 2019, Rio de Janeiro, Brazil
Sao Paulo, 2019
7 S.
International Conference on Multiphase Flow (ICMF) <10, 2019, Rio de Janeiro>
Fraunhofer IPA ()
Beschichtung; drop-on-demand; Nicht Newton'sche Flüssigkeit

Numerical and experimental studies on the generation of viscous droplets based on a Drop-on-Demand device have been performed. Interface method VOF (volume-of-fluid) in a CFD-code was applied to predict the paint droplet formation. A dynamic mesh model was used to simulate the valve tappet movement. Liquid filling process in the nozzle and liquid pinch-off outside the nozzle were investigated in detail. A parametric study was carried out at first with Newtonian viscous fluids to obtain the parameter dependence for a droplet generation and process optimization. Dimensionless numbers, such as Weber-Number and Capillary number were used. In order to account for the effects of non-Newtonian behaviors of paint liquids, both shear thinning and elongation viscosity models were then applied for the calculation of liquid thread and droplet formation. Validations of the used models as well as the simulation results were carried out using experimental measurements.