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- PostDynamic Behaviour of a Fixed-end Square Hollow Section Steel Column Subjected to Wind Flow(2022) Arafat, Ahmad; Chalmers tekniska högskola; Yao, Huadong; Yao, HuadongSteel lattice structures are widely used in the structural engineering. These structures are light in weight and usually all structural elements are exposed to wind. This forms that fact that wind loads are highly dependent of the cross-section of structural elements. Although there are several design codes available for assigning wind loads on lattice structures such as Eurocode - EN 1991-1-4 (2005), the resulted assigned wind loads in these codes are conservative and considering the upper bound solution. Additionally, these codes do not provide clear procedure for investigating the dynamic behaviour of the lattice structures. Therefore, this project has been directed towards investigating the dynamic behaviour of a fixed-end square hollow section steel column under wind flow. To carry out this project, finite element analysis (FEA) and computational fluid dynamics (CFD) analysis were coupled. The first analysis was built using Abaqus, where the material and boundary conditions of the column were assigned. The second analysis was composed of two steps, where the first step has been aimed to carry out a quasi-steady simulation using STAR-CCM+. Whereas, in the second step, codes of Abaqus and STAR-CCM+ were coupled. As expected, the column under wind loading will have wind-induced vibration frequencies in both directions (X and Y). The major frequency (in X-direction) is less dependent on mesh size and Time-step. Nevertheless, the minor frequency (in Y-direction) is highly dependent on the mesh size and Time-step, and has lower amplitude. Finally, calculation according to Eurocode reveals conservative results in comparison with the numerical solutions.
- PostFluid-Structure Interaction; Stiffness Effects on Airfoil Flutter: A numerical study of airfoil flutter in STAR-CCM+(2022) Tylén, Oskar; Chalmers tekniska högskola; Yao, Huadong; Yao, HuadongThis report looks in to the phenomenon called flutter, a type of flow induced vibration in structures occurring at specific flow conditions. Specifically, the project looks at how flutter affects airfoils, and how the structural stiffness of the airfoil impacts the flutter effects at a certain set of conditions. The analysis was carried out using commercial CFD solver STAR-CCM+. Within this software, the structural dynamics of a symmetric NACA0012 airfoil were modeled as a two-degree-of-freedom system with one bending mode and one torsional mode. Due to constraints on computational power and time, the mesh generation was adjusted to reduce computational time as much as possible without it effecting the behaviour of certain parameters, particularly the aerodynamic lift coefficient which was considered an important performance measure for the airfoil. The results indicate that with a given set of operating conditions, adjusting the structural stiffness can be used as an effective countermeasure against flutter. However due to the mesh limitations mentioned above, the quality of the results can be questioned when looking closer at the flow field and numerical instabilities effecting some parameters.