SINOPSIS

A transition element for incompressible Navier-Stokes flows easing the merge of computational domains with different finite element (FE) mesh refinements is deviced : only normal balance of heat flow and fluid momentum (through the viscous shear forces) is enforced, with variable linking parameters that can be fixed by the user and differ from one problem to the other. Particular cases are the impervious boundary between non mixing flows or the completely permeable boundary where temperature and velocities continuity is assumed in the weak sense. Independent meshes with their own refinements can then be merged easily with very little topological interaction, while retaining (nearly) complete physical interaction. The effectiveness of the transition element has been validated on academic computational examples dealing with 2-D situations and applied to thermal control problems encountered in electronic devices where local power dissipations, thin channels and their boundary flows require local refinements which would otherwise diffuse through the whole computational domain and yield untractable models.