Resumo:
The present work consists of the study of two phenomena involved in fluid-structure interaction analysis, that is, the ground effect and Vortex-Induced Vibrations (V.I.V.). The purely Lagrangian Discrete Vortex Method is used for the numerical solution of the forced oscillation problem on a circular cylinder immersed in a fluid flow, with the body having a degree of freedom to oscillate only in the in-line direction, that is, in the streamwise direction. Under these conditions, there is an intense interaction between fluid and structure, and complex phenomena that characterize V.I.V. studies are manifested, such as the appearance of different regimes of formation and structural vortex shedding, the competition between these regimes and the phenomenon of synchronous coupling, lock-on, or lock-in. For the study and accuracy of fluid dynamic loads in the situation of forced vibration, this work contributes to the theoretical development and numerical implementation in the calculation of inertial effects in the integral formulation of the specific stagnation enthalpy. Separately, investigations are carried out regarding the influence caused purely by the proximity of a flat surface to the cylinder immersed in a flow using a numerical artifice which decouples the boundary layer originated along the flat wall, which produces a similar effect to the situation where the ground moves at the same speed as the fluid. The occurrence of phenomena such as the change in the stagnation point and the separation points of the boundary layer on the stationary bluff body, significant variations in the loads and suppression of the vortex shedding regime when the distance between the ground and the cylinder is very small were verified. In the end, investigations were carried out where situations of ground and V.I.V. effects are simultaneously present, investigating the dominance of one phenomenon over the other in situations where the effects were adverse. All simulations are performed for a Reynolds number equal to 105. In general, the studies had excellent correspondence with the literature. However, a study involving a similar situation with the performance of the two interference effects is rarely found in the literature for comparison.
