The Cadarache CEA/IRESNE R&D unit on nuclear system modelling investigates passive safety devices to minimize the flow of water out of the reactor vessel of a pressurized water reactor and to manage the water reserves available for safety injections, in the event of a loss-of-coolant accident. These devices, such as in-vessel flow limiters or advanced accumulators, operate on the principle of hydraulic diodes, to prevent or delay core dewatering and its possible degradation.
The subject of this thesis is the Penalized Direct Forcing numerical modeling of turbulent thermal-hydraulic flows under various spatial discretizations. The technique of introducing a direct forcing term into the Navier-Stokes equations allows obstacles to be taken into account in an incompressible flow. It combines projection and velocity penalization methods. It leads to a natural treatment of boundary conditions for pressure correction at the edges of obstacles. The doctoral student will build on the achievements of two recent PhD theses, dedicated to the simulation of laminar or turbulent flows using the PDF method in Finite-element spatial discretization using a scalar model of turbulence. He/she will extend this work to other spatial discretizations (Finite-Element Volumes, Finite-Difference Volumes) and to turbulence-model evolution equations.
The computational methodology will be verified/validated on test cases and applied to the simulation of hydraulic diodes envisaged for passive safety systems in nuclear reactors.
The doctoral student will develop competence in thermohydraulics simulation and numerical methods.