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Drop impact is common in industrial applications and nature. As in the 3D printing, the drops squeezed out of the nozzle do not have to take on a spherical shape. This paper delves into the role of drop shape in drop impact with solidification under the 3D printing conditions. To track the rapidly evolving liquid-gas interface, the Cahn-Hilliard-based phase field method is employed. The solid-liquid interface is tracked by the liquid fraction. The model is discretized using an explicit finite difference scheme on a half-staggered grid. The code was written in FORTRAN and enhanced with the OpenMP technique. After being validated against experimental data, the model was applied to various cases. Moreover, the paper took into account a number of factors influencing drop impact and solidification dynamics, such as aspect ratio, contact angle, and thermal contact resistance. It was found that the aspect ratio exerts little effect on drop profile for the cases under consideration when solidification is on, but that the contact angle could drastically reduce freezing time, converting the convex solidfication pattern to a concave one. [ABSTRACT FROM AUTHOR]

In thermal spraying, molten YSZ (Yttria Stabilized Zirconia) drop impact is crucial to the understanding of formation of splats and hence coatings. However, existing studies hardly cast attention to the possible rebounding dynamics when successive molten YSZ drops impinge onto newly solidified splats whose temperature is still high so that freezing may be delayed. This work uses a newly developed numerical model based on the conservative level set method to probe into the rebounding dynamics of YSZ drops in practical thermal spraying conditions. The free-energy-based surface tension model in the phase field method was introduced to avoid the computing of curvature, which is however necessary in the continuum surface tension model. The projection method was invoked to solve the Navier–Stokes equations. The model was validated against an experiment of drop impact with rebounding, showing reasonable agreement. Moreover, the model was applied to both dense and hollow YSZ drop impact, with the details of fluid flow being analyzed. The maximum spread factor was found in agreement with existing scaling laws. [ABSTRACT FROM AUTHOR]