Oscillatory flow convection in a melted pool

Abstract

A two‐dimensional laser surface remelting problem is numerically simulated. The mathematical formulation of this multiphase problem is obtained using a continuum model, constructed from classical mixture theory. This formulation permits the construction of a set of continuum conservation equations for pure or binary, solid‐liquid phase change systems. The numerical resolution of this set of coupled partial differential equations is performed using a finite volume method associated with a PISO algorithm. The numerical results show the modifications caused by an increase of the free surface shear stress (represented by the Reynolds number Re) upon the stability of the thermocapillary flow in the melting pool. The solutions exhibit a symmetry‐breaking flow transition, oscillatory behaviour at higher values of Re. Spectral analysis of temperature and velocity signals for particular points situated in the melted pool, show that these oscillations are at first mono‐periodic them new frequencies appear generating a quasi‐periodic behaviour. These oscillations of the flow in the melted pool could induce the deformation of the free surface which in turn could explain the formation of surface ripples observed during laser surface treatments (surface remelting, cladding) or laser welding.