Multiscale simulation of electrostatic powder coating sprays

Powder coating is a finishing process used in various industries where electrostatically charged particles are sprayed onto metal surfaces. High-fidelity simulation is becoming increasingly popular to optimize this technique. However, the current standard approaches based on modeling the individual particles require substantial computational effort, which limits their practical application. To alleviate this drawback, the multiscale pseudo-direct numerical simulation method (P-DNS) is extended for the study of the turbulent flow of charged particles. In an offline process, representative volume elements (RVEs) are simulated considering the particles and their interactions with the surrounding gas and electrostatic field, and the dynamic response of the mixture is homogenized. On the global scale, where a continuous field for the particulate phase is used, the effects of turbulence and coupling forces are obtained by evaluating synthetic models of the RVEs with local dimensionless parameters. Additionally, a coat film model is presented to quantify the coating layer thickness on the target surface. The numerical tool is first validated with experimental data from the literature. Then, it is applied to the coating of a surface of complex geometry, analyzing the impact of particle diameter, applied voltage, and spray gun trajectory. The reliable results obtained with modest resources confirm the potential of the methodology as a rapid predictive tool in processes involving this coating technology.