Estruturas de seção circular sob ação de vento via simulação numérica de alta delidade

Abstract

Slender structures of towers and chimneys commonly have circular cross-sections and are repeatedly subjected to wind action capable of inducing signi cant vibrations to the structure due to the phenomenon of vortex detachment. The cylindrical or tapered structures are more susceptible to this phenomenon than those with great cross-section variation. Therefore, it is of fundamental importance to understand how the ow develops around the structure. In this perspective, the present study focuses on the development of high delity numerical simulations of the ow around rigid xed circular structures. Initially, a case of tapered structure under a transitional regime, from laminar to turbulent, is studied, and the results are compared with numerical results available in the literature. In sequence, a series of 8 cases are developed considering two types of geometry, cylindrical and tapered, under di erent conditions of permanent and transient ow. The wind speed pro le con- guration is admitted as uniform and shear, at high Reynolds numbers; some cases are compared with experimental results available in the literature. The solution of the incompressible Navier-Stokes equations in 3D is obtained by 3D Computational Fluid Dynamics (CFD), using the nite element method, considering Smagorinsky’s LES turbulence model.The results emphasize the three-dimensional e ects from the variation of the incident wind velocity and the diameter along the height as well as the top e ect on the ow characteristics related to the vortex shedding phenomenon. These e ects are revealed as a function of a dimensionless parameter proposed for this purpose, which expresses the magnitude of these gradients.