Hauggaard-Nielsen, Anders Boe1; Damkilde, Lars2; Krenk, Steen3
1 Department of Structural Engineering and Materials, Technical University of Denmark2 Department of Civil Engineering, Technical University of Denmark3 Lund Institute of Technology
Phase change problems, occurring e.g. in melting, casting and freezing processes, are often characterized by a very narrow transition zone with very lareg changes in heat capacity and conductivity. This leads to problems in numerical procedures, where the transition zone propagates through a mesh fixed in space. An iterative time-stepping method has been developed within a finite element context which improves upon present methods in three ways: a flux based evaluation of the conductivity matrix replaces the traditional temperature based method, a predictor is introduced for the properties in the mid-point of the current time step and full energy balance is restored in each iteration by adjusting the local temperature. Examples demonstrate improved accuracy, a reduction of the numerical disturbances introduced by the passage of the transition zone and a smaller number of timesteps needed compared with other methods currently in use.