Interaction fluide-structure pour des configurations multi-corps. Applications aux liaisons complexes, lois de commande d'actionneur et systèmes souples dans le domaine maritime.

摘要

The aim of this work is to develop a coupling between two solversin order to study complex mechanical systems which are in stronginteraction with a fluid. The co-simulation provides the ability tocarefully model without significant approximations the fluid physics,the dynamics of the mechanical systems and their coupling. TheReynolds-averaged Navier-Stokes equations for incompressible,isothermal, turbulent and multiphase flows are solved by ISIS-CFD.The mechanical problem is solved by MBDyn which is an open-source solver dedicated to dynamic multi-body systems. A generaland formal formulation of the coupling problem is realised using theSteklov-Poincaré formulation. An implicit, efficient and stablecoupling algorithm is proposed, tested and validated. The algorithmstabilisation is achieved through a relaxation operator whichdepends on the added mass effects. Thus, a method to evaluatethe added mass effects is implemented in ISIS-CFD. Due to thefinite-volume formulation adopted in this solver, this method isgeneral. For instance, complex geometries or the free surfacedeformation can be taken into account. Moreover, the proposedalgorithm does not require any modifications to be made to bothsolvers. Only the implementation of interfaces is required. Inaddition, it is shown that the number of iterations to reach aconverged state, is of the same order when the kinematics aresolved or when the motion is known in advance and imposed(optimal configuration). The coupling algorithm is validated on thefollowing cases: vortex induced motions of simple shapes,evaluation of the transfer functions of a frigate in regular headwaves, computation of the motion of very low density bodies(strong anisotropic added mass effects), analysis of the roll decayof a frigate with active fins (control of actuators) and simulation of amoored ship in shallow water disturbed by a nearby ship (breakingof mooring lines). Two simulations with flexible beams are alsopresented. The framework is proven to be efficient for all the abovecases. For instance, the computed transfer functions of a frigate inregular head waves are in good agreement with experimental dataand the effect of the stabilizer fins on the roll decay of a frigate isperfectly captured.