The Influence of Surface Deformation on Thermocapillary Flow Instabilities in Low Prandtl Melting Pools with Surfactants

Abstract

Heat and fluid flow in low-Prandtl number melt pools (Pr = O(10 −1)) 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 deformation 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 volumeof-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.

The Effects of Process Parameters on Melt-pool Oscillatory Behaviour in Gas Tungsten Arc Welding

“…Each simulation was executed in parallel on 80 cores (AMD EPYC 7452) of a computing cluster for a total run-time of about 800 h. To reduce the computational costs associated with running the model, possible developments can focus on performing model order reduction or decreasing the spatial and temporal resolutions of the simulations. Reliability, validity and grid independence of the present numerical model in predicting internal flow behaviour, evolution of the melt-pool shape and surface oscillations were meticulously verified in our previous works [71,53,72,18]. Moreover, the frequencies acquired from the present three-dimensional numerical simulations deviate less than 10% from the experimental data reported by Yudodibroto [73].…”

The Effect of Groove Shape on Molten Metal Flow Behaviour in Gas Metal Arc Welding

“…The adjustment factor was employed to negate changes in the total heat input due to changes in surface morphology [ 52 , 53 ], which is defined as follows: …”

“…To implement the source terms in the governing equations and the surface tension model, user-defined subroutines programmed in the C programming language were used. The computational domain contains about 2.7 × 10 6 non-uniform hexahedral cells, with the smallest cell spacing being set to 80 μm in the melt-pool region, which is sufficiently fine to obtain grid-independent solutions [ 35 , 36 , 52 , 53 ]. The cell spacing increases gradually from the melt-pool region towards the boundaries of the computational domain and the maximum cell size was limited to 400 μm.…”

The Effect of Groove Shape on Molten Metal Flow Behaviour in Gas Metal Arc Welding

“…with in meters and I in Ampere. The adjustment factor F q was used to negate changes in the total heat input due to surface deformations [52,53], which is defined as follows:…”

“…non-uniform hexahedral cells, with the smallest cell spacing being set to 80 µm in the melt-pool region, which is sufficiently fine to obtain grid-independent solutions [39,40,52,53]. The cell spacing increases gradually from the melt-pool region towards the boundaries of the computational domain and the maximum cell size was limited to 400 µm.…”