Integrated modeling and validation for phase change with natural convection

Water-ice systems undergoing melting develop complex spatio-temporal interface dynamics and a non-trivial temperature field. In this contribution, we present computational aspects of a recently conducted validation study that aims at investigating the role of natural convection for cryo-interface dynamics of water-ice. We will present a fixed grid model known as the enthalpy porosity method. It is based on introducing a phase field and employs mixture theory. The resulting PDEs are solved using a finite volume discretization. The second part is devoted to experiments that have been conducted for model validation. The evolving water-ice interface is tracked based on optical images that shows both the water and the ice phase. To segment the phases, we use a binary Mumford Shah method, which yields a piece-wise constant approximation of the imaging data. Its jump set is the reconstruction of the measured phase interface. Our combined simulation and segmentation effort finally enables us to compare the modeled and measured phase interfaces continuously. We conclude with a discussion of our findings

Thermal Behavior and Geometry Model of Melt Pool in Laser Material Process

Melt pool geometry and thermal behavior control are essential in obtaining consistent building performances, such as geometrical accuracy, microstructure, and residual stress. In this paper, a three dimensional model is developed to predict the thermal behavior and geometry of the melt pool in the laser material interaction process. The evolution of the melt pool and effects of the process parameters are investigated through the simulations with stationary and moving laser beam cases. The roles of the convection and surface deformation on the heat dissipation and melt pool geometry are revealed by dimensionless analysis. The melt pool shape and fluid flow are considerably affected by interfacial forces such as thermocapillary force, surface tension, and recoil vapor pressure. Quantitative comparison of interfacial forces indicates that recoil vapor pressure is dominant under the melt pool center while thermocapillary force and surface tension are more important at the periphery of the melt pool. For verification purposes, the complementary metal oxide semiconductor camera has been utilized to acquire the melt pool image online and the melt pool geometries are measured by cross sectioning the samples obtained at various process conditions. Comparison of the experimental data and model prediction shows a good agreement