Modelling turbulent thermofluid flow in stationary gas tungsten arc weld pools

The effects of turbulence in stationary gas tungsten arc (GTA) welds in AISI 304 stainless steel were examined using a finite element themofluids model. The model includes buoyancy, Lorentz and Marangoni driven fluid flow, a large deformation model of the free surface, and a k-epsilon turbulence model. To facilitate implementation of the wall function boundary conditions for the k-epsilon turbulence model, a dynamic numerical grid remapping technique was used to clearly separate elements in the liquid from those in the solid. The influences of sulphur content of AISI 304 stainless steels on the turbulent viscosity, fluid flow, and weld pool dimensions were simulated. Good correlation between experimentally observed and predicted weld pool shapes and dimensions was obtained. Also, the effect of sulphur concentration on AISI 304 weld pool dimensions was correctly predicted. The simulations indicate that the flow in such stationary GTA weld pools in AISI 304 stainless steel is not laminar and that quantitatively accurate predictions of weld pool fluid flow and weld shapes and dimensions will only be possible if the effects of turbulence in GTA weld pools are modelled correctly.