Estudo de vibrações induzidas por vórtices em um corpo rombudo utilizando o método de vórtices discretos com modelo de rugosidade superficial

Abstract

In the literature, there is scarcity of tests with combined effects of vortex-induced vibrations (VIV) and rough surface to control drag force behaviour of bluff bodies. In this context, the present work contributes to the limited studies on the surface roughness effects into the VIV of a single circular cylinder. The body is forced to oscillate with respect to the free stream. The numerical approach utilizes a purely Lagrangian description through the Discrete Vortex Method (DVM) with surface roughness model. Previous works in the literature have also demonstrated that two-dimensional roughness model is more sensitive than a single turbulence modeling to capture nonlinear multi-physics phenomenon with a variety of applications in different engineering areas. In the present results, the dimensionless oscillation amplitude was fixed at A/D = 0.13 (D is the outer cylinder diameter) and the body oscillation frequency varied in the range 0.04 ≤ f0 ≤ 0.80. These values were chosen to compare with experimental data, when possible. Three relative roughness sizes were chosen, i.e. ε/D = 0.001, 0.0045 and 0.007. The test cases with no roughness effects, when compared to the experimental data, captured two basic antisymmetrical modes, namely modes AI and AIV, and also the chaotic mode. The symmetric mode with coalescence was captured. Those modes indicate that the vortex shedding frequency, obtained from the time history curve of the drag coefficient force, is synchronized with the body oscillation frequency at a fixed Reynolds number of 100,000. In certain tests involving the surface roughness model, a desynchronization between the forced and vortex shedding frequencies was observed, and significant drag force variations, representing the main contribution of this study.