Title: A Variational Projection Scheme for Nonmatching Surface-to-Line Coupling between 3D Flexible Multibody System and Incompressible Turbulent Flow,
Abstract: This paper is concerned with the partitioned iterative formulation to
simulate the fluid-structure interaction of a nonlinear multibody system in an
incompressible turbulent flow. The proposed formulation relies on a
three-dimensional (3D) incompressible turbulent flow solver, a nonlinear
monolithic elastic structural solver for constrained flexible multibody system
and the nonlinear iterative force correction scheme for coupling of the
turbulent fluid-flexible multibody system with nonmatching interface meshes.
While the fluid equations are discretized using a stabilized Petrov-Galerkin
formulation in space and the generalized-$\alpha$ updates in time, the
multibody system utilizes a discontinuous space-time Galerkin finite element
method. We address two key challenges in the present formulation. Firstly, the
coupling of the incompressible turbulent flow with a system of nonlinear
elastic bodies described in a co-rotated frame. Secondly, the projection of the
tractions and displacements across the nonmatching 3D fluid surface elements
and the one-dimensional line elements for the flexible multibody system in a
conservative manner. Through the nonlinear iterative correction and the
conservative projection, the developed fluid-flexible multibody interaction
solver is stable for problems involving strong inertial effects between the
fluid-flexible multibody system and the coupled interactions among each
multibody component. The accuracy of the proposed coupled finite element
framework is validated against the available experimental data for a long
flexible cylinder undergoing vortex-induced vibration in a uniform current flow
condition. Finally, a practical application of the proposed framework is
demonstrated by simulating the flow-induced vibration of a realistic offshore
floating platform connected to a long riser and an elastic mooring system.