FEM technique for convective - diffusion problems with moving boundary

Heat transfer is often in practice joint with solid-liquid phase change and convection in the liquid phase. The subdomain where flow of the liquid phase takes place changes then its shape in time. As an example of a such process the ground freezing with flowing groundwater is analysed in the paper. The flow of the groundwater is assumed to be incompressible. The velocity of the groundwater is related to the velocity potential by Darcy's law. As a consequence this potential is described by Laplace equation. The temperature distribution is described by standard unsteady - state heat conduction equation with convective term in the unfrozen part of the domain and Stefan's boundary condition on the phase change interface. Both the groundwater flow and the temperature field are calculated using FEM. The original technique is proposed, because the unfrozen part of the domain, where the groundwater flows, changes its shape in time.