Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Archives of Thermodynamics

2 2003

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Eulerian equilibrium and non-equlibrium macroscopic modelling of binary system solidification

Banaszek J., Furmański P., Browne D.

Archives of Thermodynamics

2003

Vol. 24, no 1

37-57

Two models of macroscopic computer simulation of binary system solidification on a fixed grid are discussed. First, it is shown that the single-domain enthalpy-porous medium model not only provides complete information on the evoluation of macroscopic entities, but also enables a detailed analysis of the role of the mushy zone properties in the progress of solidification. In this context, the results of FEM calculations for aqueous ammonium chloride solutions are presented showing the importance of anisotropy of permeability and thermal conductivityof the mushy zone. Next, to account for non-equilibrium phenomenon of the constitutional undercooling a new front tracking technique on a fixed grid, which is based on the kinetics of dendritic growth, (see a companion paper [13]), is used. The model is compared with the enthalpy approach showing its superiority in the detection of the undercooled zone in front of dendrite tips and, thus, in modelling of columnar /equiaxed grain structures. It is, then, further used to address the question of the influence of alloy composition on the size of the undercooled liquid zone in front of columnar dendrite tips during solidification of Al-Cu alloys driven by conduction in a square mould. Eventually, a possible scenario of the coupling of both models, in order to develop a comprehensive computer simulation of binary alloys solidification driven by both conduction and natural convection, is outlined.

An interface-tracking model of moving boundaries in multi-phase systems: application to solidification

Browne D., Hunt J.

Archives of Thermodynamics

2003

Vol. 24, no 1

25-36

A new approach to modelling of phase boundary migration is presented. In particular, a meso-scale model of alloy solidification, which can resolve solid grain boundaries as they grow through the diminishing liquid phase, has been developed. The initial condition is of a superheated, but cooling, liquid alloy in a domain with a mixed thermal boundary condition. After activation via nucleation of solid, the model tracks the phase boundaries as discrete fronts across a fixed computational grid, and the kineticsof motion are derived from theories of dendritic growth. Each interface is formed by interpolation between representative computational markers, and is the boundary between liquid and partial solid with a dendritic morphology. The model simulates the non-equilibrium growth of both a columnar front and equiaxed grains, and can thus be used to predict the final grain structure in metallic alloy castings. The evolution of microstructure and heat are fully coupled in the formulation. The method is illustrated by the example of the simulation of Al-Cu alloy solidification.