Abstract
When painting complex surfaces, such as large-curvature surfaces, poor coating quality is often obtained, which may be caused by lack of an appropriate atomization model, insufficient understanding of atomization mechanisms and laws, and improper painting parameters. This paper presents a numerical model of paint atomization of air spraying using the volume-of-fluid method and large eddy simulation. The interface capture and the turbulent flow were mainly considered in the model: the former was tracked by the volume-of-fluid method and the latter was predicted by the large eddy simulation. After the computational domain being meshed by the staggered-grid method, the governing equations were discretized by the finite volume method and were solved by the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) Consistent algorithm. The results of numerical simulations show that the characteristics of atomization flow field, such as velocity variation, pressure distribution, and paint volume fraction are in agreement with the regularities of atomization. Moreover, the primary and secondary atomization phenomena can be clearly observed: as soon as the paint issues from the nozzle, the paint flow begins to distort and the paint fragments continuously eject from the main paint flow and then these paint fragments distort and disintegrate into smaller elements. A comparison with the experimental data from the literature proves that the model of the whole atomization process of air spray is effective. The model is suitable for simulating the whole atomization process and easy to obtain initial conditions, which can be applied to set the appropriate painting parameters and study paint atomization mechanisms and laws in depth.
Highlights
Painting robots have been widely applied in the manufacture of airplanes [1], ships [2], automobiles [3] and other industrial products [4]
Modeling the paint atomization process to study the atomization mechanisms and regularities in depth is of great significance for solving the quality-control problem of painting complex surfaces
The VOF method computes the volume fraction of a particular phase and is naturally volume-conserved, it can track interface location and topology as accurately as possible, and has been widely used in fuel injection modeling [18,19,20]. Turbulence modeling is another problem in modeling paint atomization of air spray, which can be solved by three methods: Reynolds averaged Navier–Stokes (RANS), direct numerical simulation (DNS) and large eddy simulation (LES)
Summary
Painting robots have been widely applied in the manufacture of airplanes [1], ships [2], automobiles [3] and other industrial products [4]. The VOF method computes the volume fraction of a particular phase and is naturally volume-conserved, it can track interface location and topology as accurately as possible, and has been widely used in fuel injection modeling [18,19,20]. Turbulence modeling is another problem in modeling paint atomization of air spray, which can be solved by three methods: Reynolds averaged Navier–Stokes (RANS), direct numerical simulation (DNS) and large eddy simulation (LES). Where u is the velocity of flow; t is time; ρ is the flow density; p is the space pressure; μ is the dynamic viscosity of flow; S is the viscous stress tensor; f is the force per unit mass; Fs is surface tension of flow
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