As a necessary step toward the quantitative predictions of macro-segregation commonly found in metal castings, classical experiments and numerical benchmarks have been used to validate a simplified binary- alloy solid...As a necessary step toward the quantitative predictions of macro-segregation commonly found in metal castings, classical experiments and numerical benchmarks have been used to validate a simplified binary- alloy solidification model. The model consists of fully coupled conservation equations for the transport phenomena （heat transfer, solute redistribution, ~tnd melt convection） that lead to macro-segregation in a solidifying ingot with a fixed solid phase. Simulations were performed for solidification of either a Pb-48wt.%Sn or a Sn-5wt.%Pb alloy in a rectangular cavity. The present predictions were compared with experimental data and numerical reference results reported in the literature. Subsequently, the model was applied to a numerical benchmark problem described in the literature for solidification of a Sn-10wt.%Pb alloy. Simulation results for flow velocity, liquid fraction evolution, and macro-segregation maps also were compared with literature predictions, showing similar trends. It is concluded that additional comparisons to experimental results are still required to assess more complex solidification models.展开更多
The aim of this paper is to numerically investigate the influence of nanoparticles shape on heat and mass transport phenomena in a moving lid cavity under the combined effect of thermo-solutal buoyancy force and magne...The aim of this paper is to numerically investigate the influence of nanoparticles shape on heat and mass transport phenomena in a moving lid cavity under the combined effect of thermo-solutal buoyancy force and magnetic force.The governing equations are transformed into velocity-vorticity form of equations and solved using Galerkin's weighted residual finite-element-technique.The analysis has been carried out with parameters like buoyancy ratio(−5≤N≤5),magnetic field inclination angle(0°≤ϕ≤90°)with four shapes of Al_(2)O_(3) nanoparticle like bricks,blades,platelets and cylinders.The results revealed that the shape factor on Nusselt number is significant depending upon the inclined magnetic field and buoyancy ratio whereas on mass transfer the shape effect is negligible.The diffusion mode of transport process is stronger than the convection mode at higher inclination angle of magnetic field.Based on a given value of N andϕ,blade and cylinder shows the best performance in Nusselt and Sherwood number respectively except the platelet shape that shows maximum frictional loss in terms of wall shear stress.展开更多
A mathematical model coupling the momentum, energy and species conservation equa-tions was proposed to calculate the macro--segregation of Fe--C alloy ingot during solid-ification. The corresponding simulation softwar...A mathematical model coupling the momentum, energy and species conservation equa-tions was proposed to calculate the macro--segregation of Fe--C alloy ingot during solid-ification. The corresponding simulation software which concurrently solves the macro-scopic mass, momentum, energy and species conservation equations has been developedby applying the SIMPLE algorithm.The thermo--solutal convection in a NH_4 Cl--H_2O ingot is verified and the result showsgood agreement with that reported. Then macro--segregation in a steel ingot is simu-lated by using the developed program. The steel ingot is in a rectangular mold with ariser. The fluid flow is mainly induced by the temperature field and the solid fraction.The macro--segregation pattern is mainly affected by the thermo--induced convectionin the mushy zone. The negative segregation forms along the walls of the casting.The positive segregation forms at the top center of the casting into the riser. Thespecies concentration reaches the peak in the center of the ingot where solidificationends lastly.展开更多
基金supported by the National Science and Technology Major Project of China(No.2011ZX04014-052)the National Basic Research Program of China(No.2011CB012900)
文摘As a necessary step toward the quantitative predictions of macro-segregation commonly found in metal castings, classical experiments and numerical benchmarks have been used to validate a simplified binary- alloy solidification model. The model consists of fully coupled conservation equations for the transport phenomena （heat transfer, solute redistribution, ~tnd melt convection） that lead to macro-segregation in a solidifying ingot with a fixed solid phase. Simulations were performed for solidification of either a Pb-48wt.%Sn or a Sn-5wt.%Pb alloy in a rectangular cavity. The present predictions were compared with experimental data and numerical reference results reported in the literature. Subsequently, the model was applied to a numerical benchmark problem described in the literature for solidification of a Sn-10wt.%Pb alloy. Simulation results for flow velocity, liquid fraction evolution, and macro-segregation maps also were compared with literature predictions, showing similar trends. It is concluded that additional comparisons to experimental results are still required to assess more complex solidification models.
文摘The aim of this paper is to numerically investigate the influence of nanoparticles shape on heat and mass transport phenomena in a moving lid cavity under the combined effect of thermo-solutal buoyancy force and magnetic force.The governing equations are transformed into velocity-vorticity form of equations and solved using Galerkin's weighted residual finite-element-technique.The analysis has been carried out with parameters like buoyancy ratio(−5≤N≤5),magnetic field inclination angle(0°≤ϕ≤90°)with four shapes of Al_(2)O_(3) nanoparticle like bricks,blades,platelets and cylinders.The results revealed that the shape factor on Nusselt number is significant depending upon the inclined magnetic field and buoyancy ratio whereas on mass transfer the shape effect is negligible.The diffusion mode of transport process is stronger than the convection mode at higher inclination angle of magnetic field.Based on a given value of N andϕ,blade and cylinder shows the best performance in Nusselt and Sherwood number respectively except the platelet shape that shows maximum frictional loss in terms of wall shear stress.
基金This work was financially supported by the National NSFC BaoSteel Conjunct Foun dation(No.50174031).
文摘A mathematical model coupling the momentum, energy and species conservation equa-tions was proposed to calculate the macro--segregation of Fe--C alloy ingot during solid-ification. The corresponding simulation software which concurrently solves the macro-scopic mass, momentum, energy and species conservation equations has been developedby applying the SIMPLE algorithm.The thermo--solutal convection in a NH_4 Cl--H_2O ingot is verified and the result showsgood agreement with that reported. Then macro--segregation in a steel ingot is simu-lated by using the developed program. The steel ingot is in a rectangular mold with ariser. The fluid flow is mainly induced by the temperature field and the solid fraction.The macro--segregation pattern is mainly affected by the thermo--induced convectionin the mushy zone. The negative segregation forms along the walls of the casting.The positive segregation forms at the top center of the casting into the riser. Thespecies concentration reaches the peak in the center of the ingot where solidificationends lastly.
