Vincent Faucher

Advanced parallel strategy for strongly coupled fast transient fluid-structure dynamics with dual management of kinematic constraints

Simulating fast transient phenomena involving fluids and structures in interaction for safety purposes requires both accurate and robust algorithms, and parallel computing to reduce the calculation time for industrial models. Managing kinematic constraints linking fluid and structural entities is thus a key issue and this contribution promotes a dual approach over the classical penalty approach, introducing arbitrary coefficients in the solution. This choice however severely increases the complexity of the problem, mainly due to non-permanent kinematic constraints. An innovative parallel strategy is therefore described, whose performances are demonstrated on significant examples exhibiting the full complexity of the target industrial simulations.

Regularized immersed boundary-type formulation for fast transient dynamics with fluid-structure interaction

Abstract The present article deals with fast transient phenomena involving fluids and structures undergoing large displacements and rotations, associated with non-linear local behavior, such as plasticity, damage and failure. In this context, classical Arbitrary Lagrangian Eulerian approaches reach a limit where it is not possible to update the fluid grid to follow the structural motion without encountering entangled fluid cells forcing the simulations to stop. So-called immersed boundary approaches are thus frequently preferred in this situation, since they allow breaking the topological connection between the fluid and structural meshes and retrieve the expected level of robustness to handle complex structural motions. Their potential for efficient, robust and accurate simulations at the industrial level has been proven. However, it appears that the classical implementation of such approaches still imposes some constraints over the fluid mesh with respect to the structural mesh in terms of cell sizes, due to the expression of the kinematic links between fluid and structural velocities, which must be improved. It is demonstrated in the present article that an extended regularized framework can be designed to overcome the current drawbacks, but it comes with a significant increase of computational complexity and requires an extension of the classical software features encountered in fast transient dynamics simulation programs.

LOCA simulation: analysis of rarefaction waves propagating through geometric singularities

The propagation of a transient wave through an orifice is investigated for applications to Loss Of Coolant Accident in nuclear plants. An analytical model is proposed for the response of an orifice plate and implemented in the EUROPLEXUS fast transient dynamics software. It includes an acoustic inertial effect in addition to a quasi-steady dissipation term. The model is experimentally validated on a test rig consisting in a single pipe filled with pressurized water. The test rig is designed to generate a rapid depressurization of the pipe, by means of a bursting disk. The proposed model gives results which compare favourably with experimental data.Copyright