Time-Implicit Integral Formulation for Fluid Flow Modelling in Congested Media

The thesis issue is the modelling of fluid flows in congested media by solid obstacles. The purpose is to design an integral approach reconciling the local and the component global scale for the numerical simulation of the coolant flow in the nuclear reactor components. The approach affords the advantage of embedding the local and 'component' representation scales in the same formalism, in ensuring the coherence between the two scales. This technique consists of a multidimensional integral formulation of the fluid flow governing equations allowing to naturally recover the CFD (Computational Fluid Dynamics) standard fluid approach when refining the mesh. The discretization is based on a time-implicit collocated finite volume numerical scheme using a pressure-correction algorithm. The scheme is relevant for weakly compressible flows and preserves the positivity of both the density and the internal energy, at the discrete level. Numerous unsteady or steady numerical tests are carried out and show the integral approach ability to simulate channel flows congested by axial or transversal rods. (author)