Modelling spray washing with Lagrangian differencing dynamics

Spray washing is commonly used in car manufacturing to clean and prepare surfaces for subsequent processes like coating and painting. It uses high-pressure spray to deliver cleaning solutions or water onto vehicle surfaces to remove dirt, oils, metal shavings, and contaminants. In the washing, for optimal washing quality, it is important to have proper nozzle arrangements, spray configuration, and vehicle positioning. Numerical simulations can be used to minimize the trial-and-error process and improve the quality. Spray washing involves strong discontinuities, fragmentation, violent free-surface changes, and complex multiphase flow, which are difficult to simulate using conventional grid-based methods. Lagrangian differencing dyanmics (LDD) [1] is a novel numerical method which has the features of being Lagrangian, meshless, and second-order accurate. It employs a meshless finite difference approximation scheme over scattered points, and solves the incompressible Navier-Stokes equations in an implicit way. It is suitable for spray simulation because of the Lagrangian and meshless properties. In this work, we apply LDD to the simulation of spray washing of a car body. Important information, including fluid reachability, surface-water contact time, drainage condition and duration, and impact forces are obtained from the simulation and the results are analyzed. The influence of nozzle arrangement and configuration are discussed.