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Drop impact dynamics with solidification has been a hot topic of research recently. However, numerical studies to that end mainly concentrate on spherical drops, paying less attention to non-spherical ones that are ubiquitous in industrial applications like additive manufacturing and plasma spraying. Therefore, a phase field model accelerated with the shared-memory parallelism OpenMP is proposed to simulate the impact of a non-spherical heavy metal droplet in actual additive manufacturing conditions. The tracking of the gas–liquid interface is realized by the finite difference solution of the Navier–Stokes equation and the Cahn–Hilliard equation. We use the liquid fraction defined all over the computational domain to distinguish between solid and fluid. The model was then employed to predict the impact and freezing dynamics of non-spherical droplets, with the focus on the effects of the aspect ratio, of the contact angle, and of the phase field mobility. It shows that the established model could well capture the axis switching process, that rebounding accompanying the axis switching process could be hindered by solidification, and that larger phase field mobility could smooth drop profile, rendering it round in the axis switching process. [ABSTRACT FROM AUTHOR]

A comprehensive numerical model has been developed, which is capable of predicting the spreading of a high-speed yttria-stabilized zirconia (YSZ) droplet with solidification microstructure formation under a horizontal electric field in plasma spraying processes. The numerical model entails the explicit finite difference solution of the Navier–Stokes equations and the energy balance equation, coupled with the Cahn–Hilliard equation to track the liquid–gas two-phase interface and with a phase field model for solidification microstructure formation involving polycrystalline growth. The electric force is added as a source term in the Navier–Stokes equations, and the fluids are assumed to be perfect dielectrics. The in-house code is written in Fortran and run in parallel. The results reveal that the retracting process could be completely inhibited using a horizontal electric field and that solidification time is greatly reduced. A new mechanism to suppress droplet breakup/splash could be realized, featuring reduction of the rising angle the spreading front makes with a substrate. All the cases show columnar grains within a splat. Besides, the model is validated against experimental results, with gratifying agreement achieved. [ABSTRACT FROM AUTHOR]

A novel numerical model was developed to investigate air entrapment in binary droplet impact with solidification microstructure formation under practical plasma spraying conditions. The evolving liquid–gas interface was tracked by the explicit finite difference solution to the Cahn–Hilliard equation, coupled with the Navier–Stokes equations. Another diffuse interface model was invoked to trace solid–liquid and grain–grain boundaries. The model was discretized using an explicit finite difference method on a half-staggered grid. The velocity pressure coupling was decoupled with the projection method. The in-house code was written in Fortran and was run with the aid of the shared memory parallelism, OpenMP. The time duration over which gas compressibility matters was estimated. Typical cases with air entrapment were studied with the model. The effect of droplet porosity on air entrapment was probed into as well: the larger the porosity of a droplet, the bigger the trapped air bubble. The grain growth near the air bubble is skewed. Moreover, a case without air entrapment was also shown herein to stress that air bubbles could be suppressed or even eliminated in plasma spraying by adjusting the landing positions of successive droplets. [ABSTRACT FROM AUTHOR]