In this contribution the multi-physics problem of fluid-structure-control interaction (FSCI) is solved by an iterative, partitioned approach utilizing Gauss-Seidel formulations. The aim is to conduct a fully coupled co-simulation of the FSCI problem, where the controller actively influences the dynamics of the structure. The purpose of this manuscript is twofold: In the first part, in order to get a profound idea of the behavior and parametric sensitivity of such systems involving multiple couplings, the simplified model problem introduced for fluid-structure interaction (FSI) by Joosten, Dettmer and Perić is extended by a generic control unit. Since a monolithic solution for this simplified model problem can be found, it is used for first investigations concerning solvability and stability. On this basis, three different variants for coupling the subsystems fluid, structure and controller by a Gauss-Seidel scheme, are derived and systematically investigated. More precisely the FSCI problem is solved without nesting of the subsystems in the first variant and with nesting of two of the respective subsystems in the second and third variant. In the second part, the resulting algorithms are applied to a complex, non-linear, multi-degree of freedom problem, which is a well-known benchmark problem in the FSI community and is therefore extended to FSCI. Applying those algorithms to the multi-degree of freedom problem shows good results and substantiates the applicability to such problems. It follows, actively influencing the dynamics of the structure in the FSCI problem by a controller reduces the structural vibrations induced by the fluid flow significantly.

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One research objective in the Priority Program 1897 "Calm, Smooth and Smart" of the German Research Foundation (DFG -SPP 1897) is the development of model order reduction techniques for parametric non-linear mechanical systems to enable efficient design, simulation, analysis, optimization and control of those. As a starting point for our research, this contribution provides an overview of the main challenges and well-established reduction techniques in this research area, at that stage, neglecting parameter dependencies. This includes simulation-based as well as simulation-free reduction bases generation and hyperreduction of the non-linear force terms. An extension of the Krylov directions in moment matching based on the concept of modal derivatives is also sketched.

This contribution gives a short introduction into the topic of fluid‐structure‐control interaction (FSCI). This is a multi‐field problem, where three fields are coupled, namely a fluid‐flow, structural dynamics and closed‐loop control of structures. The interactions are identified as surface‐coupling of fluid flow and structural dynamics as well as signal‐coupling of structural dynamics and closed‐loop control. At first a simple model problem is introduced, which allows an efficient investigation of the convergence behavior and stability of such kind of problem. In this context an iterative partitioned approach, using a serial Gauß‐Seidel scheme, is presented. Finally, the insights gained by the model problem are used to set up a multi‐dimensional numerical experiment. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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