Vorticity based turbulence model for thermofluids modelling of welds

A comprehensive thermofluids model of stationary gas tungsten arc welding (GTAW) has been developed and used to examine the effects of thermofluids phenomena on the predicted temperatures and flow field in the weld pool, as well as their impact on the resultant weld pool dimensions in 304 stainless steel and 6061 aluminium plates. A dynamic numerical grid remapping technique was used within the finite element based model to model the geometry of the solid/liquid interface and free surface of the weld pool. Initial work showed that correlation between experimental and predicted weld pool dimensions was only possible provided that the effects of turbulence were modelled using a well posed k - turbulence model. However, the two-equation k - turbulence model introduces additional complexity and requires considerable additional computational effort. To overcome these shortcomings, a simpler vorticity based turbulence model has been developed in which the turbulent viscosity and thermal conductivity are based upon the magnitude of the vorticity in the flow field as predicted through solution of the continuity, momentum and energy equations. Excellent correlation was obtained between the weld pool dimensions predicted by the vorticity based turbulence model, the predictions from the k - turbulence model and the experimental data from welds made in 304 stainless steel with three different sulphur impurity concentrations and in 6061 aluminium. The advantage of the vorticity based turbulence model is that it is significantly less computationally intensive than the standard k - turbulence model and has, therefore, the potential of providing tractable and practical computations of fully three-dimensional welding processes.