Verification of a numerical model of macrosegregation in direct chill casting

Purpose - This paper aims to point out the critical problems in numerical verification of solidification simulation codes and the complexity of the verification and to propose and apply a procedure of generalized verification for macrosegregation simulation. Design/methodology/approach - A partial verification of a finite-volume computational model of macrosegregation in direct chill (DC) casting of binary aluminum alloys, including the coupled transport phenomena of heat transfer, fluid flow and species transport, is performed. The verification procedure is conducted on numerical test problems, defined as subproblems with respect to the complexity of the physical model, geometry, and boundary conditions. The studied cases are thermal convection with solidification in DC casting, thermal natural convection of a low-Prandtl-number liquid metal in a rectangular cavity and 1D directional solidification of a binary Al-Cu alloy. Grid-convergence studies, code comparison with an alternative Chebyshev-collocation method, and comparison with a reference similarity solution are used for verification. Findings - An excellent ability of the model to accurately resolve the thermal convection in the pertinent range of Prandtl and Rayleigh numbers is shown. Concerns regarding the solution of species transport in the mushy zone remain. Research limitations/implications - The proposed verification procedure is not completed in its entirety. Further verification of the solutal and thermosolutal convection problems is required. Originality/value - This paper proposes verification techniques for complex coupled solidification problems involving significant convection in the melt.