A multi-scale simulation method for powder coating with moving powder guns

A mathematical model and numerical method, supported by experiments, to simulate industrial scale powder coating for moving coating guns is developed. The numerical method is based on a model reduction procedure that starts with a three species electrostatic model for the negative corona discharge at the nozzle exit of the gun. It is reduced to a one species electrostatic model away from the gun, which is coupled to a RANS fluid model and Lagrangian particle tracking and charging in a detailed stationary simulation. The final part consists of coating simulation with a moving gun, enabled by immersed boundary methods that do not require a body fitted mesh. In the coating simulation the detailed simulation results are reinjected, preserving the size and charge distribution of the powder particles. The method is validated with coating thickness measurements for horizontal and vertical lines on flat and two sets of bent panels: towards and away from the applicator. The bent panels are used to validate the performance on highly convex and concave objects.