No abstract

No abstract

In this work, we propose a numerical investigation of the main flow field characteristics around a free oscillating rigid circular cylinder that is immersed in a turbulent flow (Re≈5∙〖10〗^4). The cylinder is characterized by high value of mass ratio and mass damping (m^*=145; ξ=0.6÷1.14∙〖10〗^(-3);m^* ξ=0.1÷0.25). Then the numerical results are compared with previous experimental data obtained in the wind tunnel under very similar fluid dynamic conditions. There are few works in literature that consider both numerical and experimental results under these conditions. This is probably due to the experimental facilities limitations and the computational difficulties correlated to modeling the flow with high Reynolds number. With the aim of matching the experimental analysis, developed in the last years in the Politecnico di Milano Wind Tunnel on a suspended oscillating cylinder, with numerical results, we set-up a numerical URANS model through a CFD commercial code using a k-ω SST turbulence model in a 3D domain.\ud The numerical setup is characterized by the use of the DFBI-Morphing (Dynamic Fluid Body Interaction) model that allows the modeling of the body motion in response to fluid forces treating the cylinder as a mass-damping-spring system by introducing spring and damping forces acting on it.\ud A preliminary check of this numerical setup was provided by a benchmark involving a simple case of fixed cylinder at the same Reynolds number, where the movements of the cylinder were disabled. The numerical results of this case have been compared with experimental and numerical results reported in literature by means of Drag and Lift coefficients and Strouhal number at high Reynolds (Re≈5∙〖10〗^4). After that benchmark, the full setup has been checked by considering specific fluid dynamic conditions where the cylinder was out of the lock in region in which the oscillations of the cylinder are negligible.\ud Finally we have investigated two points of the steady state oscillating response curve of the cylinder in the lock in region. The numerical model gave good results in terms of amplitude response of the cylinder and aerodynamic forces if compared with experimental results.\ud The analysis of the numerical reconstruction of the flow field evolution are therefore considered to have more information on the vortex shedding mode especially in the transition region between 2S and 2P mode

The recent developments in numerical tools and computing resources seem to provide a suitable environment to perform numerical analyses of Fluid-Structure Interaction problems. The Co-Simulation technique, in particular, develops the idea of coupling a CFD software with a structural one in order to simulate complex FSI phenomena with a partitioned approach, stressing the concept of software modularity. In this way, it is possible to adopt software tools at the cutting edge of technology. Nonetheless, several difficulties may arise in the choice of the partitioning scheme and of the algorithmic details for the step-by-step time integration. This paper deals with the application of the Co-Simulation technique to a benchmark case experimentally investigated in previous works: the vortex-induced vibrations (VIV) of a beam supported sphere (that is, a sphere fixed to the end of a slender cantilever beam) in a free surface flow. This problem is challenging although apparently simple and it seems quite absent from literature so far. In this paper, the computational issues are thoroughly investigated and the model is validated by comparison with the experimental data. In this way, a robust framework is created in order to deal with VIV problems