URANS SIMULATIONS USING OPENFOAM
Fredi Cenci1; André Luís Condino Fujarra1
1 Universidade Federal de Santa Catarina
doi:10.20906/CPS/CILAMCE2017-0838
Resumo
Cylindrical geometries are frequently present in offshore structures such as monocolumns and spar oil platforms. The flow around these structures may result in complex vortex shedding systems, hence resulting in undesirable vibrations and motions known as Vortex Induction Vibration (VIV) and Vortex Induction Motion (VIM) phenomena. This article shows how to perform a URANS simulation of a two-dimensional clamped cylinder using the Open source Field Operation and Manipulation (OpenFOAM) as a basic approach of offshore platforms. The primary target of this paper are beginners in CFD modeling, thus it presents details and relevant information about the set up process as well as the verification and validation analysis. This paper gradually built a two dimensional clamped cylinder test case at subcritical region (Re = 10000), then process 18 cases varying the time step and number of cells, following with the verification and validation procedure. All cases were analyzed quantitatively upon drag and lift coefficients and Strouhal number, and qualitatively upon the flow visualization. The study recovered the main vortex-shedding present in experiments, also found secondary vortex present in the near wall behind the cylinder, the last reported in others numerical studies. This article has shown that URANS simulation is deeply dependent of a set of computational parameters and they must be carefully investigated in order to achieve reliable results. In addition, the process of verification and validation have exposed an essential role in numerical studies due to the variety of error sources that may lead to inaccurate results. Further, the problem approached in this article could be the initial investigation for futures CFD modeling of real offshore oil platforms.
Palavras-chave: Vortex shedding ; Computer fluid dynamics; Clamped cylinder