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Membranes constitute an important category of thin‐walled and in particular tensile structures [1], for which in contrast to shells their structural rigidity is obtained by means of prestress rather than relying on bending stiffness. In particular, the structures considered in this study act in pure membrane state and have no bending stiffness. A big challenge of such structures is finding the shape of static equilibrium. This is not a trivial task since not every shape under any prestress distribution or loading condition renders a static equilibrium configuration. This is even more prominent when prestressed cables are attached to the structure. To overcome this problem for general tensile structures, various types of form‐finding methods were developed [2, 3]. In this study, the Updated Reference Strategy (URS) [4, 5] is presented in combination with multipatch isogeometric analysis [6] as discretization method. The enforcement of the continuity constraints along the common patch interfaces [7] is realized using a Nitsche‐type method [8] while the results are evaluated and compared with the Penalty‐based approach [9]. [ABSTRACT FROM AUTHOR]

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) [ABSTRACT FROM AUTHOR]

Abstract: Uncertainty quantification for multi‐physics problems like fluid‐structure interaction (FSI) is challenging in terms of the required computational effort and complexity of physics involved. A Multilevel Monte Carlo (MLMC) approach for stochastic analysis of FSI problems is presented in the current study. An overall reduction in computational cost is achieved by variance reduction in MLMC method. The efficacy of MLMC algorithm for expensive problems like FSI is compared with classical Monte Carlo(MC) method and MLMC is found to achieve the required accuracy at a significantly reduced computational cost. An FSI benchmark test case with uncertain inputs is presented here. The possibility of uncertainty quantification for FSI systems with a plausible computational cost using MLMC is demonstrated. [ABSTRACT FROM AUTHOR]

Lightweight shell structures have gained significant popularity in the engineering design as they offer high load carrying capacity for low cost. While classical Finite Element models of such structures have been extensively used in practice, the shell formulations for Isogeometric Analysis (IGA), particularly for Kirchhoff‐Love shell structures [1], have demonstrated benefits arising from the smooth geometry description and the highly accurate solutions that are enabled. Moreover, the direct use of CAD‐models for the structural simulations is possible based e.g. on the Isogeometric B‐Rep Analysis (IBRA) [2]. Herein the application of IBRA to Fluid‐Structure Interaction (FSI) simulations of wind turbines is demonstrated, thus naturally extending IBRA to coupled multiphysics problems. [ABSTRACT FROM AUTHOR]

Following the growth of computational fluid dynamics in engineering applications, adjoint methods for sensitivity analysis are being applied to an increasing range of industrial problems. In recent years, growth in computational power has led to widespread use of high‐fidelity, time‐resolved techniques, such as large‐eddy simulation, for applications, including bluff‐body aerodynamics, where time‐averaged equations may be less reliable. The solution of time‐dependent adjoint equations, however, becomes unstable in time as the Reynolds number increases and the flow becomes chaotic. The source of this instability has been explained by analysis of the system's Lyapunov exponents and several solutions have been proposed in the literature based on least‐squares shadowing. Currently, such techniques impose a higher computational cost compared to classical adjoint methods and may become infeasible when the number of unstable Lyapunov exponents is large. In this work, we explore a more recently proposed approach, which balances the adjoint energy source term with added artificial dissipation. The stability of this approach is investigated for a discrete adjoint solver based on the time‐dependent incompressible Navier‐Stokes equations. The accuracy of the resulting shape sensitivities is analyzed using a linear regression technique for the flow around a circular cylinder. [ABSTRACT FROM AUTHOR]

Due to their easy‐to‐shape and light‐weight characteristics, membranous structures are common in modern civil engineering. As all outside buildings they are exposed to wind loads and consequently undergo fluid‐structure interactions (FSI). In order to dimension these membranous constructions and to avoid the damage of the material by FSI, numerical and experimental investigations are necessary. The current paper presents the simulation part of complementary experimental and numerical investigations relying on an advanced numerical simulation methodology. [ABSTRACT FROM AUTHOR]