Modelling of particle impact using modified momentum source method in thermal spraying

Abstract

Thermal spraying is a coating process in which the feedstock material is accelerated and impacts on a substrate in form of molten or semi-molten particles. Particle impact simulation is helpful for understanding the coating build-up during thermal spraying. In this study, a computational fluid dynamics (CFD) model, based on the volume of fluid (VOF) approach, is used to model the impact and solidification of nickel particles on a flat substrate in 2D and 3D. Temperature dependent viscosity and momentum source are commonly used for solidification modelling. The former is accurate, but computationally too expensive for multiple particle impact simulations. In the momentum source method, the momentum equation of the particle is manipulated in order to reduce its velocity to zero as it solidifies. ANSYS Fluent employs this method for solidification. However, this method is proven to be inadequate for the simulation of multiple-particle solidification. In the context of this study, a modification to this method has been introduced. Temperature dependent viscosity and validated numerical studies from literature are used to validate the modified method. The developed method is proven to be capable of simulating the deposition of a 60 μm thick coating in a more feasible computational time, in comparison to temperature dependent viscosity method.