Université Paris-Est (ÉdF R&D/CETMEF/École des Ponts ParisTech)

Interaction of fluids and structures is a key issue for a variety of physical systems. The range of examples that come to mind easily in the engineering domain is vast and covers all the scales: from bio- and medical- (where the scale of problems is often less than a millimeter) to Civil Engineering (where it can be hundreds of meters). As fluid and structure computational mechanics are mainly carried out by different scientific communities, a partitioned approach is a natural choice when FSI problems are tackled.

In this talk, we present a strong coupling strategy, based on a differential method, where forces and displacements are directly exchanged between a fluid and a structure solver. This partitioned approach is subject to the known added-mass effect when coupling incompressible flows with structures, that can lead to instability. Therefore, the stability need to be mathematically studied [1]. To enlarge the stability area and to decrease the total number of iterations, dynamic relaxation is used and show good performances with inexpensive external computations. For the structure we use a Finite Elements code (FEAP) and for the fluid a Finite Volume standalone software (OpenFOAM), both able to use advanced models in their field of application. The coupling is insured using the Component Template Library (CTL) [2], an efficient middleware for scientific computing that allows the communication between existing codes programmed in different languages with good performances.

This implementation was validate on 2D examples, and applied to 3D cases with advances models (e.g. incompressible flows with complex free-surfaces in interaction with a non-linear structures) [3].

[1] C. Kassiotis, A. Ibrahimbegovic, R. Niekamp, and H. G Matthies. Nonlinear ﬂuid-structure interaction problem. Part I: implicit partitioned algorithm, nonlinear stability proof and validation examples. Computational Mechanics, 47:305–323, 2011.

[2] C. Kassiotis, A. Ibrahimbegovic, R. Niekamp, and H. G. Matthies. Nonlinear ﬂuid-structure interaction problem. Part II: space discretization, implementation aspects, nested parallelization and application examples. Computational Mechanics, 47:335–357, 2011.

[3] C. Kassiotis, A. Ibrahimbegovic, and H. G. Matthies. Partitioned solution to ﬂuid-structure interaction problems in application to free-surface ﬂows. European Journal of Mechanics – B/Fluids, 29:510–521, 2010.