Study of Convective Non-Newtonian Alloy Solidification in Molds by the PSIMPLER/Finite-Volume Method

Abstract

A numerical study is made of the solidification of an Al-Si alloy with 1.5-2% Si in a graphite mold, considering the pseudo-plastic behavior of the liquid alloy, based on a non-Newtonian model of the power law with n = 0.5. The fluid mechanics and heat transfer description of the transient convection-diffusion model is made using the finite-volume method. The pressure-velocity-temperature coupling is made using a new sequential algorithm called PSIMPLER which is validated by comparing it with the results from the literature for Newtonian fluid behavior solved with the SIMPLE algorithm. The stability and efficiency of the PSIMPLER method is also determined by solving natural convection and mixed convection in rectangular cavities with SIMPLE. The final results make it possible to infer that the Newtonian or non-Newtonian nature of the convection model affects the time and shape of the solidification process. It is concluded that the PSIMPLER algorithm allows the use of subrelaxation coefficient values close to one for the velocities, decreasing calculation time by more than 50%.