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Abstract. We report on an international effort to develop an open-source computational environment for high-fidelity fluid-structure interaction analysis. In particular, we will focus on verification of the implementation for application in computational aeroelasticity. The capabilities of the SU2 code for aeroelastic analysis have been further enhanced both by developing natively embedded tools for the study of largely deformable solids, and by wrapping it using Python tools for an improved communication with external solvers. Both capabilities will be demonstrated on relevant test cases, including rigid-airfoil solutions with indicial functions, the Isogai Wing Section, test cases from the AIAA 2nd Aeroelastic Prediction Workshop, and the vortex-induced vibrations of a flexible cantilever in the wake of a square cylinder. Results show very good performance both in terms of accuracy and computational efficiency. The modularity and versatility of the baseline suite allows for a flexible framework for multidisciplinary computational analysis. The software libraries have been freely shared with the community to encourage further engagement in the improvement, validation and further development of this open-source project.

This paper describes a new framework for Fluid-Structure Interaction (FSI) modelling within the open-source code SU2. SU2 has been developed to solve complex, multi-physics problems described by Partial Differential Equations (PDEs), with an emphasis on problems involving aerodynamic shape optimization. Due to its modularity, the code provides an appropriate infrastructure for the solution of physical problems in several disciplines. This work provides SU2 with new tools that expand its capabilities in the fields of structural analysis and FSI. The focus will be on geometrically-nonlinear deformable solids in low-speed external flows.A Finite Element (FE) structural solver, able to deal with geometrical and material non-linearities in a static and a dynamic setting, has been built within the framework of SU2 alongside the existing solvers. Following the original object-oriented architecture in C++, a new structure compliant with the CFD solver has been developed. These new features will serve as a basis for future developments of FE-based strategies for the solution of PDEs. The structural solver has been coupled with the original fluid solver in SU2 using a partitioned approach. The structure of the code was fully recast to allow analysis across multiple zones and physical problems, currently limited to problems involving fluid and structural analysis. Both loosely-and strongly-coupled strategies are available for the solution of the coupled FSI problem.Finally, the validity of the implementations is assessed by studying the behavior of a rigid square with a flexible cantilever at low Reynolds number. The results obtained demonstrate the capabilities of these new developments and further address the physics behind this benchmark problem. * Graduate Student, Department of Aeronautics, 363A Roderic Hill Building; r.sanchez-fernandez14@imperial.ac.uk. AIAA Student Member.

This paper presents the results of numerical and experimental investigations on the force coefficients and Strouhal numbers of circular segments considering different corner angles or chord to sagitta ratios. The research is motivated because these geometries are becoming increasingly popular in several engineering disciplines. The so-called D-section (semi-circular cylinder with a corner angle of 90 •) has been experimentally studied in the past, since it is a galloping prone geometry. However, there is a lack of research for cases with different corner angles, and the numerical investigations related to this topic are particularly scarce. In this work, a 2D Unsteady Reynolds Averaged Navier-Stokes approach has been adopted aiming to study the circular segments at the sub-critical regime, considering corner angles from 40 • to 90 • , and the flow parallel to the rectilinear side. These sections were found to be particularly challenging since they present massive flow separation on the rectilinear side, alongside the inherent difficulties related to modeling the flow along curved surfaces at high Reynolds numbers. The impact of introducing low-Reynolds-number and curvature corrections in the k − ω SST turbulence model and the performance of the Transition SST model have been extensively studied.

The design of a modular tensegrity grid requires the determination of its selfstress states, before choosing an appropriate combination defining the system's initial stresses. However, the computation of the vectorial basis associated with selfstress states generally produces results that are difficult to exploit. We therefore propose two different strategies to identify and localize selfstress states in a modular tensegrity grid more pertinently. The first is based on a heuristic approach that exploits the system's structural composition of modularity and regularity. The second is numerical and aims at redefining the vectors of the basis in a more convenient and useful way. Two methods based on transformations of the vectorial basis of selfstress states have been developed for a minimal number of involved components. Finally, we suggest a selfstress state classification based on the number of components and their localization as well as on their mechanical behavior.