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The effect of triple helical grooves on the suppression of vortex-induced vibration (VIV) of a circular cylinder was investigated experimentally in a wind tunnel over Reynolds number in the range of 1 × 104 < Re < 4 × 104. It was found that the helical grooves were effective in suppressing VIV with the peak amplitude reduction of approximately 36%. In addition, the lock-on region was also reduced. To explore the mechanism for the suppression of VIV, experiments on flow structures for a stationary grooved cylinder were also conducted in a wind tunnel at a free stream velocity U∞ of 4.37 m/s, corresponding to a Reynolds number based on the bare cylinder diameter of about 3500. The data were then analyzed using the phase-averaged method to evaluate the coherent vortex structures in the wakes. The results for the stationary grooved cylinder showed that the grooves weakened vortex shedding in the near wake. In addition, the grooves also reduced the drag coefficient by 6.6%. These results help explain the reduction of VIV using helical grooves.

The mathematical model of vortex-induced vibrations (VIV) on long-span bridges is important to predict nonlinear structural responses. Such models can be divided into two categories: wake-oscillator and single-degree-of-freedom (SDOF) models. The SDOF model is widely used for wind-induced vibration calculations. However, the traditional SDOF model based on the standard van der Pol oscillator cannot simulate VIVs with multistability. In this study, a newly generalized van der Pol model is proposed to incorporate the limit-cycle oscillation (LCO) with multiple amplitudes, and the nonlinear damping is expressed by polynomial expansion. Next, the multiple LCO amplitudes can be determined from the energy evolution formula derived from the averaging method. Similarly, the evolution of the vibration amplitude during the transient response is also derived by the same method. Subsequently, nonlinear parameter identification methods based on constraint optimization are derived according to both the LCO amplitude and transient responses. In the last part of this study, the “energy map” is proposed to present the energy extracted from the fluid–structure interaction with different wind speeds and vibration amplitudes, and it is constructed by the parameters identified in the lock-in range of VIV. The “energy map” can provide a complete picture of the evolution of the energy of VIVs on bridge decks.

In this paper, fatigue analysis of oil offloading lines (OOLs) in the floating production storage and offloading (FPSO) catenary anchor leg mooring (CALM) buoy offloading system under wave and current loads in the West Africa Sea area is carried out by the numerical simulation method. The hydrodynamic coupling response is calculated, and fatigue damage is analyzed. Firstly, the numerical model is verified by comparison with the experimental results. Then, according to the environmental statistics in West Africa, the influence of various parameters on the fatigue damage of OOLs is analyzed, including tension characteristics, wave parameters, and structural parameters. Additionally, the effect of current load is studied. Results show that accumulated fatigue damage mainly occurs near the CALM buoy and is mainly caused by the 0° wind wave. Appropriately reducing the cover length of buoyancy material and increasing the wall thickness can reduce fatigue damage. Moreover, the effect of the shuttle tanker can increase the fatigue damage of the OOL near the CALM buoy by about 1.5 times, and the effect of vortex-induced vibration can increase the fatigue damage of the OOL in the middle part by up to 5–10 times.

The Vortex Self-Induced Vibration (VSIV) is a complex phenomenon, less explored than the traditional Vortex Induced Vibration (VIV), and its understanding is very important to be discussed and analyzed to determine the riser-fluid interaction on deep waters for the oil & gas industry. It may represent an additional source of fatigue in the riser design when the Floating Production Unit (FPU) imposes vertical motions at the riser top, caused mainly by the wave action, inducing vibrations in the riser plane, causing vortex-shedding and provoking oscillatory motions out of the riser plane. To deal with fundamental aspects of such a rich phenomenon, a numerical assessment of experiments with an elastically mounted cylinder exposed to an oscillating flow is carried out in the present paper. To this end, the experiments conducted by Sumer and Fredsøe were used as reference. For the numerical simulations, two types of models were investigated: one based on Computational Fluid Dynamics (CFD), the Discrete Vortex Method (DVM), and other based on a semi-empirical method, the Phase Synchronization Method (PSM), both in two-dimensional domains. Several parameters involved in DVM and PSM models need to be calibrated, and some of them are discussed in this paper. In principle, it is important to highlight that both numerical approaches were not developed for the purpose of application of prescribed motion, but for the classical VIV phenomenon, with a constant current, becoming challenging to reproduce numerically the experimental results. Besides, comparisons on scaled models are very challenging to be reproduced numerically, and another point raised in this paper is how to perform the numerical and experimental post-processing of time series to generate comparable results of relevant aspects of the phenomenon. This study represents a first step towards applying the DVM or PSM methods on risers in full scale and with different types of configurations.

In this study, uncertainty analysis of the vortex-induced vibration (VIV) tests, using a VIV test rig is presented. The VIV test rig is set up on the circulation channel in Ata Nutku Ship Model Testing Laboratory at Istanbul Technical University (ITU). The tests are performed using an elastically mounted rigid and smooth circular cylinder in low mass-damping and high Reynolds numbers conditions. The cylinder has one-degree-of freedom. It is allowed to move perpendicular to the flow while inline vibrations are constrained. The aim of the study is to demonstrate and establish a repeatable procedure to predict the uncertainty of VIV tests, utilizing some example applications of existing ITTC recommendations. Within this aim, five distinct VIV tests are carried out following ITTC guidelines and procedures measuring the amplitude (A*) and frequency response (f*) data. Uncertainty analysis study is performed for three different flow velocities, chosen from VIV tests and total uncertainty is calculated by root mean square values of precision and bias uncertainties. The precision uncertainty is predicted using response amplitude values obtained from five sets of VIV tests. The bias uncertainty is predicted utilizing the basic measurements and test results of the components of response amplitude for the cylinder. The results have demonstrated that the current test rig has low uncertainty level. Additionally, it has succeeded to reflect the characteristics of VIV phenomenon in the studied Reynolds number range, which is in the Transition Shear Layer 3 (TrSL3) flow regime. Consequently, it is believed that this study would help in spreading the application of the uncertainty analysis for VIV tests in the future.

Vortex-induced vibration (VIV) is a typical of large amplitude vibration for slender structure. Predicting the amplitude and wind speed range for VIV is vital and challenging in the wind-resistance design. The 4:1 rectangular cross-section cylinder is one of the representative structure for fundamental wind-induced vibration analysis. In this study, a novel wake-oscillator model tailored for predicting VIV in a 4:1 rectangular cylinder is proposed. Besides structural responses, this model can also conceptually reproduce the shedding behaviors of the vortices around the cylinder. For this purpose, two oscillators are employed and attached to the structure in the model. Oscillator 1, mounted on the rear face, simulates the swaying motion of the wake vortex. Oscillator 2, attached to the windward face, represents the variations in the main vortices generated from the leading edges. Governing functions of the two oscillators are derived according to the zero circulation assumption of the target region. The parameters are determined with accordance to both the rigid and aero-elastic model tests. The model’s validity is examined through the comparison of the predicted response amplitudes with experimental data. Results demonstrate that the model can effectively predict the cylinder’s responses across various Scruton numbers, using a single set of model parameters. This model is further applied to investigate the underlying mechanics of VIV excitation, focusing on the provided wind load and vibrating frequencies of Oscillators 1 and 2. These analyses helps to understand the structural VIV phenomenon.

The wind-induced vibration of cables has been widely studied over the past decades because of cables’ many applications in cable-stayed, suspension, and tied-arched bridges, and power transmission lines. They have been mostly investigated through research conducted on rigid model cables with a finite length and circular cross-sectional geometry that represents a section model of a long cable. These models have been considered accurate because the behavior of flow over a cable and circular cylinder is similar, although there are structural differences between them. Cables usually experience small- to large-amplitude vibration due to wind loads that causes fatigue failure and poses a significant threat to the safety and serviceability of these structures. Although this paper mainly focuses on reviewing the past studies about different types of wind-induced cable vibration, some general information related to circular cylinders has been briefly reported for better understanding of the flow over cables. This paper incorporates an extensive review based on the existing papers about different sources of wind-induced cable vibration consisting of vortex-induced vibration, rain-wind-induced vibration, dry galloping, ice galloping, and wake galloping. Furthermore, this paper explains the mechanism, vibration source, and a mitigation solution for each type based on the past studies using wind tunnel experiments, computational fluid dynamics, field measurements, or analytical approaches. This review helps to better understand the aerodynamics and fluid–structure interactions of cables with or without ice/rain on the surface, while static and dynamic wind loads act on the structure.

Wind energy is a promising renewable energy source for a low-carbon society. This study is to develop a fully packaged vortex-induced vibration triboelectric nanogenerator (VIV-TENG) for scavenging wind energy. The VIV-TENG consists of a wind vane, internal power generation unit, an external frame, four springs, a square cylinder and a circular turntable. The internal power generation unit consists of polytetrafluoroethylene (PTFE) balls, a honeycomb frame and two copper electrodes. Different from most of the previous wind energy harvesting TENGs, the bouncing PTFE balls are fully packaged in the square cylinder. The distinct design separates the process of contact electrification from the external environment, and at the same time avoids the frictional wear of the ordinary wind energy harvesting TENGs. The corresponding VIV parameters are investigated to evaluate their influence on the vibration behaviors and the energy output. Resonant state of the VIV-TENG corresponds to the high output performance from the VIV-TENG. The distinct, robust structure ensures the full-packaged VIV-TENG can harvest wind energy from arbitrary directions and even in undesirable weather conditions. The study proposes a novel TENG configuration for harvesting wind energy and the VIV-TENG proves promising powering micro-electro-mechanical appliances.

As a fundamental fluid-structure interaction (FSI) phenomenon, vortex-induced vibrations (VIVs) of circular cylinders have been the center of the FSI research in the past several decades. Apart from its scientific significance in rich physics, VIVs are paid great attentions by offshore engineers, as they are encountered in many ocean engineering applications. Recently, with the development of research and application, wake-induced vibration (WIV) for multiple cylinders and galloping for VIV suppression attachments are attracting a growing research interest. All these phenomena are connected with the flow-induced vibration (FIV). In this paper, we review and give some discussions on the FIV of offshore circular cylinders, including the research progress on the basic VIV mechanism of an isolated rigid or flexible cylinder, interference of multiple cylinders concerning WIV of multiple cylinders, practical VIV suppression and unwanted galloping for cylinder of attachments. Finally, we draw concluding remarks, give some comments and propose future research prospects, especially on the major challenges as well as potentials in the offline/online modelling and prediction of real-scale offshore structures with high-fidelity CFD methods, new experimental facilities and applications of artificial intelligence tools.

Vortex-induced vibration (VIV) systems with stiffness nonlinearity have received increasing attention because the stiffness nonlinearity can broaden the effective flow velocity range for energy harvesting or achieve broadband VIV suppression. Reduced-order mathematical models are useful when it is necessary to analyze and optimize a VIV-based system with stiffness nonlinearity. However, the accuracy of existing reduced-order models in simulating the VIV of a structure with nonlinear stiffness remains unknown. This investigation proposes to predict the VIV of a circular cylinder with nonlinear stiffness using harmonically forced vibration data. The transverse force coefficients of a circular cylinder at a Reynolds number of Re  = 150 are identified based on computational fluid dynamics (CFD) simulations with harmonically forced vibrations. The forced vibration data are utilized to predict the VIV responses of a circular cylinder with cubic nonlinear stiffness and a circular cylinder with a nonlinear energy sink (NES) attachment. The predictions based on forced vibration data are compared with free vibration CFD simulations to validate the accuracy of the proposed method. Numerical examples suggest that the forced vibration data can qualitatively and to some extent quantitatively predict the VIV responses of the considered nonlinear systems. Hence, the reduced-order model with forced vibration data can serve as an effective tool for analyzing and optimizing VIV systems with stiffness nonlinearities.