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The flow around circular smooth fixed cylinder in a large range of Reynolds numbers is considered in this paper. In order to investigate this canonical case, we perform CFD calculations and apply verification & validation (V&V) procedures to draw conclusions regarding numerical error and, afterwards, assess the modeling errors and capabilities of this (U)RANS method to solve the problem. Eight Reynolds numbers between Re = 10 and Re=5×105 will be presented with, at least, four geometrically similar grids and five discretization in time for each case (when unsteady), together with strict control of iterative and round-off errors, allowing a consistent verification analysis with uncertainty estimation. Two-dimensional RANS, steady or unsteady, laminar or turbulent calculations are performed. The original 1994 k-ω SST turbulence model by Menter is used to model turbulence. The validation procedure is performed by comparing the numerical results with an extensive set of experimental results compiled from the literature.

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After one decade of experimental investigation, the Vortex-Induced Motion – VIM phenomenon deserves a comprehensive survey concerning the advances related to its understanding, mainly under the consideration of the fundamental aspects that keep it in a close relationship to the dynamic behavior of the same phenomenon acting on slender bodies, the well known Vortex-Induced Vibration – VIV. A considerable amount of results can be found in the literature, although there are few works dealing with a general view of the problem. Probably, the main reason for such a large amount of works with no interaction between themselves and, consequently, without a common understanding about VIM might be due to its technological origin, featured by huge platforms with a variety of geometrical details, which ends up placing the researches more on the field of the faithful reproduction of the features in small-scale and less on the global understanding of the phenomenology regardless the floating system, e.g. a spar platform, a monocolumn or even a semi-submersible or a tension-leg platform. Obviously, no one should disagree that there is part of the research that must keep a faithful relationship with the full scale, however, in most of them it is possible to identify the common fundamentals concerning the fluid-structural interaction. The aim of the present work is to address a comprehensive evaluation of the experimental investigations during the past decade on the VIM, trying to gather a general understanding about its phenomenology including some comparisons to VIV. As a result, some relevant aspects are pointed out for a more prospective way of research.

A great deal of works has been developed on the spar vortex-induced motion (VIM) issue. There are, however, very few published works concerning VIM of monocolumn platforms, partly due to the fact that the concept is fairly recent and the first unit was only installed last year. In this context, a meticulous study on VIM for this type of platform concept is presented here. Model test experiments were performed to check the influence of many factors on VIM, such as different headings, wave/current coexistence, different drafts, suppression elements, and the presence of risers. The results of the experiments presented here are motion amplitudes in both in-line and transverse directions, forces and added-mass coefficients, ratios of actual oscillation and natural periods, and motions in the XY plane. This is, therefore, a very extensive and important data set for comparisons and validations of theoretical and numerical models for VIM prediction.

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The flow around free-surface piercing, low aspect-ratio circular cylinder is investigated by means of unsteady Reynolds averaged Navier-Stokes (URANS) calculations together with verification procedures and comparison with small-scale experimental and Particle Image Velocimetry results. A two-phase interface capturing model is used to handle the free-surface flow, together with k-ω SST turbulence model. We investigate physical and modeling aspects of this problem in order to gain more knowledge about the interaction of free-surface and free-end effects so that this mechanism is better understood and taken into account when modeling the problem in engineering-applied situations, such as the vortex induced motion of spars, tension-leg platforms and semi-submersibles. The case herein presented is a captive, low aspect-ratio cylinder (L/D = 2.0) with flow velocity corresponding to Reynolds and Froude numbers (both based on diameter) of Re = 4.3 × 104 and FnD = 0.31, respectively. We will show that appreciable free-surface effects are perceived on the flow, but with dominance of free-end effects, at least in terms of forces. Furthermore, we investigate different boundary conditions that would represent this free-surface problem to show that the separation of viscous and free-surface effects is not valid in this instance. Therefore, the interaction between viscous and free-surface effects is also tangentially investigated. In order to support our conclusions, we will show forces with uncertainty estimation and field variables obtained with different modeling strategies, unveiling physical and numerical aspects of this problem.