Numerical simulation of molten pool dynamics in high power disk laser welding

► This paper describes the modeling process of heat source and driving forces in disk laser welding to analyze the heat transfer and fluid flow in weld pool. ► Calculated fusion zone profile is in good agreement with the experimental result. ► The effects of laser beam profile (Gaussian vs. measured), vapor shear stress, vapor heat source and sulfur content are analyzed. ► The effects of beam profile, vapor shear stress and Marangoni flow by sulfur addition are insignificant. ► Vapor heat source has a profound effect on the upper part of the molten pool shape.