A hybrid sharp-diffuse interface approach to accurately model melt pool dynamics with rapid evaporation in laser-based processing of metals

2026-06-17

AI Summary

This work addresses the challenge in laser metal processing where conventional diffuse-interface methods fail to accurately resolve the steep thermal gradients across the gas–liquid interface, leading to inaccurate predictions of vapor recoil pressure and surface tension. To overcome this limitation, the authors propose a hybrid interface modeling strategy that combines a sharp-interface CutFEM approach for high-fidelity heat conduction with a level-set-based diffuse-interface single-fluid finite element method for multiphase flow simulation. Coupling between the two solvers is achieved through a narrow-band temperature field extension. The resulting framework preserves robustness in capturing complex interfacial dynamics while significantly enhancing interfacial temperature accuracy, achieving second-order spatial convergence in the thermal model. Compared to purely diffuse-interface approaches, the method permits mesh sizes two orders of magnitude larger at equivalent accuracy, yielding an overall improvement of one order of magnitude in solution accuracy for representative test cases.

Abstract

Predictive simulation of melt pool dynamics in laser-based processing of metals, e.g., laser beam welding or laser powder bed fusion additive manufacturing, requires accurate resolution of thermo-hydrodynamic interactions at the melt-gas interface. Here, evaporation-induced recoil pressure and temperature-dependent surface tension govern the flow. Because these mechanisms depend sensitively, often exponentially, on the interface temperature, reliable predictions demand highly accurate heat transfer models. Popular diffuse-interface formulations smear the extreme thermal gradients as typical for laser-metal interactions, leading to interface temperature errors that critically degrade the accuracy of interface force predictions and melt pool dynamics. We present a hybrid sharp-diffuse interface approach for high-fidelity modelling of melt pool thermo-hydrodynamics with rapid evaporation. The heat transfer problem is represented using a sharp-interface unfitted finite element (CutFEM) formulation, enabling accurate prediction of the temperature field. The multi-phase flow problem, characterized by large density ratios and complex interface dynamics, is accurately captured using a robust level-set-based one-fluid diffuse-interface finite element formulation. Consistent coupling is achieved by extending the sharp-interface temperature into a narrow interface region to evaluate temperature-dependent interface forces within the diffuse-interface flow framework. In practically relevant benchmarks, the sharp-interface thermal model exhibits second-order spatial convergence, enabling finite element sizes two orders of magnitude larger than the diffuse-interface approach for 1 accuracy. In a novel coupled thermo-hydrodynamic benchmark representative of laser-metal interactions, the hybrid approach is one order of magnitude more accurate than a purely diffuse-interface model on the same mesh. Robu

Problem

• melt pool dynamics
• laser-based metal processing
• sharp-diffuse interface
• evaporation
• thermo-hydrodynamics

Innovation

• hybrid sharp-diffuse interface
• melt pool dynamics
• CutFEM
• level-set method
• laser-metal interaction