The influence of surface deformation on thermocapillary flow instabilities in low Prandtl melting pools with surfactants

TL;DR

This study uses advanced 3D numerical simulations to show that surface deformations significantly influence thermocapillary flow instabilities in laser melting pools with surfactants, improving prediction accuracy.

Contribution

It introduces a comprehensive numerical model that incorporates surface deformations and a dynamic heat source to better predict melt pool behavior during laser processing.

Findings

Surface deformations increase flow instability predictions.

Including surface effects improves melt pool morphology accuracy.

Dynamic heat source modeling affects energy absorption predictions.

Abstract

Heat and fluid flow in low Prandtl number melting pools during laser processing of materials are sensitive to the prescribed boundary conditions, and the responses are highly nonlinear. Previous studies have shown that fluid flow in melt pools with surfactants can be unstable at high Marangoni numbers. In numerical simulations of molten metal flow in melt pools, surface deformations and its influence on the energy absorbed by the material are often neglected. However, this simplifying assumption may reduce the level of accuracy of numerical predictions with surface deformations. In the present study, we carry out three-dimensional numerical simulations to realise the effects of surface deformations on thermocapillary flow instabilities in laser melting of a metallic alloy with surfactants. Our computational model is based on the finite-volume method and utilises the volume-of-fluid (VOF) method for gas-metal interface tracking. Additionally, we employ a dynamically adjusted heat source model and discuss its influence on numerical predictions of the melt pool behaviour. Our results demonstrate that including free surface deformations in numerical simulations enhances the predicted flow instabilities and, thus, the predicted solid-liquid interface morphologies.