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Recently, the phenomenon of tail-sustained swaying of the 160 km/h EMU in single-track tunnels has gained much attention, especially for the rear-powered vehicle. This phenomenon is investigated from the perspective of aerodynamic fluid–structure coupling vibration in this study. The aerodynamics simulation model of the train in tunnels and the multi-body dynamics model of the rear-powered vehicle were respectively established through the software of XFlow and Simpack, and then the fluid–structure coupling vibration was simulated by using real-time data dynamic exchange between the two models. Moreover, the carbody's vibration acceleration and the aerodynamic loads acting on the carbody under various wheel–rail contact geometrical conditions were discussed. Finally, the train tail swaying in field was tested, and the dominant frequencies were analyzed. The results show that the periodic aerodynamic loads and the frequency locking effect caused by the coupled vibration are the main factors for ride comfort deterioration. The violent vibration caused by fluid–structure coupling is named vortex-induced vibration (VIV) in some industries such as bridge and submarine pipeline. For the vehicle in this work, with the decrease of equivalent conicity in wheel–rail contact, the amplitude of carbody swaying increases owing to the carbody hunting, which enhances the fluid–structure coupling vibration, and further deteriorates the ride comfort. The swaying of the carbody is dominated by the vehicle hunting frequency, and the improvement of vehicle lateral stability can weaken this phenomenon. [ABSTRACT FROM AUTHOR]

The Vortex-Induced Vibration (VIV) phenomenon can cause fatigue damage. Usually, countermeasures are implemented to mitigate the VIV amplitudes. However, its cost is high. Therefore, approaches have been developed to avoid VIV at an early stage of design. Most such studies have focused on avoiding the coincidence of the vortex shedding frequency with the natural frequency of the structure and delaying VIVs by including geometrical changes to the leading and trailing edges in order to divide the oncoming flow. In this study, a new framework is proposed to find the optimal deck cross-sectional shape of Trans-Tokyo Bay Bridge, based on Reliability-Based Design Optimization (RBDO) and aiming to mitigate the VIV effects under uncertainty. Validation of the optimal designs is conducted via Computational Fluid Dynamics (CFD) simulations for different target reliability indices. [ABSTRACT FROM AUTHOR]

The existence of water-filled barriers alters the cross-sectional shape of the main girder, which may lead to vortex-induced vibrations (VIVs) in suspension bridges. However, the mechanism and occurrence conditions of VIVs in the main girder that is affected by water-filled barriers are still unclear. To this end, this study investigates the effect of water-filled barriers on the VIV performance of suspension bridges. The evolution of the vortex structure during one VIV cycle and the corresponding pressure variations, including the average and fluctuating values on the surface, were analyzed. Additionally, the spatiotemporal distribution of the surface pressure was studied using proper orthogonal decomposition (POD). The results show that VIV occurs in the main girder when the height of the water-filled barriers exceeds a threshold value of 0.317. Moreover, a significant negative pressure vortex occurred when the barriers were installed. The vortex underwent the following distinct phases in one VIV cycle: generation, separation, reattachment, and shedding. However, the negative pressure vortex behind the barrier did not vary substantially when the water-filled barriers were installed without VIV. Additionally, the average pressure on the surface of the main girder remained constant regardless of the occurrence of VIVs. In the presence of VIVs, the pressure fluctuations became much more pronounced and were mainly concentrated on the top surface and leading edge of the main girder. Additionally, the dominant modes of the pressure variations correlated with the evolution of the vortices and pressure distribution. [ABSTRACT FROM AUTHOR]

To analyze the dynamic response of a rigid M-shaped jumper subjected to combined internal and external flows, a one-way coupled fluid–structure interaction process is applied. First, CFD simulations are conducted separately for the internal and external fluid domains. The pressure histories on the inner and outer walls are exported and loaded into the finite element model using inverse distance interpolation. Then, FEA is performed to determine the dynamic response, followed by a fatigue assessment based on the obtained stress data. The displacement, acceleration, and stress distribution along the M-shaped jumper are obtained. External flow velocity dominates the displacements, while internal flow velocity dominates the vibrations and stresses. The structural response to the combined effect of internal and external flows, plus the response to gravity alone, equals the sum of the structural responses to internal flow alone and external flow alone. Fatigue damage is calculated for the bend exhibiting the most intense vibration and higher stress levels, and the locations with significant damage correspond to areas with high maximum von Mises stress. This paper aims to evaluate multiple flow fields acting simultaneously on subsea pipelines and to identify the main factors that provide valuable information for their design, monitoring, and maintenance. [ABSTRACT FROM AUTHOR]

This paper delves into the dynamics of the pipe-in-pipe system, crucial in offshore oil and gas exploration, featuring an inner drill string nestled within an outer riser. A reduced-order model with five degrees of freedom is proposed to capture the coupled dynamics of this system. Here, the inner drill string is depicted as a torsional-lateral coupled rotor constrained by the outer riser. In contrast, the outer riser is modeled as a suspended stator subjected to vortex-induced excitations and contact forces. The model incorporates nonlinearities, including dry frictions, collisions, loss of contact, and nonlinear damping through the van der Pol wake oscillator. This comprehensive model allows an in-depth exploration of the dynamics of the coupled pipe-in-pipe system. The research revealed that the overall coupling frequency of the PIP system is slightly lower than the natural frequency of a single riser. Additionally, vortex-induced vibration of the pipe-in-pipe system predominantly occurs near the coupling frequency (cross-flow vibration) and its second frequency (in-line vibration). Furthermore, the coupling frequency and its higher harmonics are significant frequency components of drill string whirl. Parametric analysis is conducted based on the non-dimensional numerical model, revealing a novel and stable whirling phenomenon termed "following whirling" at low rotary speeds of the drill string. This phenomenon arises from a combination of vortex-induced vibration and dry friction. During this stable following whirling, the riser's vortex-induced vibration traces an "8"-shaped trajectory, while the drill string follows suit, oscillating between forward- and backward-whirling, forming a "C"-shaped trajectory relative to the riser. Additionally, within the frequency lock-in region of the vortex-induced vibration, frequency analysis indicates induced nonlinear resonances through the continuous contact whirling of the drill string, showcasing a strong coupling between the drill string and the riser. In contrast, within the non-lock-in region, the system dynamics are primarily dominated by the backward whirling of the drill string. Furthermore, the parametric study reveals that the backward whirling of the drill string can significantly reduce both the cross-flow and the in-line vortex-induced vibration of the riser. However, as a side-effect, the backward whirling of the drill string can lead to higher-frequency vibrations, potentially causing fatigue damage to both the outer riser and the inner drill string. This research lays a foundation for comprehending the coupled dynamics of pipe-in-pipe systems in offshore drilling applications. [ABSTRACT FROM AUTHOR]

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Vortex-Induced Vibration (VIV) is a complex fluid–structure interaction in offshore structures. Traditionally, this phenomenon is considered periodic; however, many of its signals show chaotic behavior. The basic model already employed by other researchers is a rigid circular cylinder with linear springs and dampers. In this work, nonlinear snapping support is used to model nonlinearity in the system. To numerically simulate the flow, Reynolds-Averaged Navier–Stokes (RANS) equations for two-dimensional incompressible unsteady flows are applied. The degree of nonlinearity of the system can be changed by manipulating γ , which is one of the geometric properties of the spring and takes values between 0 and 1. The 0–1 test, Poincaré section, and Fast Fourier Transform are used to analyze the cylinder and lift force behavior. Also, the Hilbert transform is applied to the signals, and the phase shift between displacement and lift force is obtained. The results show that the system behavior consists of branches: branch I and branch II. The large amplitudes occur in branch II. It is found that chaos emerges at the beginning of branch II, regardless of the value of γ. By raising the γ value, the span of branch II becomes more expansive, and its first point is placed at lower reduced velocities. Also, the wake dynamics becomes more regular at the end of branch I and more irregular at the beginning of branch II with the increase in γ. When the cylinder displacement signal is chaotic, the lift force behavior is also chaotic, but not vice versa. [ABSTRACT FROM AUTHOR]

Based on VIV time histories growing from still to limit cycle oscillations, the motion-amplitude dependence of the VIV loading model is determined. Energy-trapping properties corresponding to the entire process of motion evolution are described by the model parameters. The influence of nonlinear mechanical damping on the VIV loading model parameter is analyzed. Prediction of VIVs under higher mechanical damping ratios is performed by the identified VIV model. The results show that, while the model parameter 휀 varies drastically with the motion amplitude, the aerodynamic damping involves gently and monotonically towards a final value corresponding to an LCO state. Neglecting the nonlinearities in mechanical damping would result in significant deviations in model parameters and predicted VIV responses. By comparing the traditional fixed-휀 model with the proposed nonlinear-휀 model, it is found that the VIVs predicted by the former are about 1.5 ∼3.0 times those predicted by the latter or tested, which underlies the necessity of consideration of motion-amplitude-dependence of an aerodynamic model. [ABSTRACT FROM AUTHOR]

The vortex-induced vibrations of two side-by-side flexible cylinders in a uniform flow were studied using a three-dimensional direct numerical simulation at Reynolds number Re = 350 with an aspect ratio of 100, and a center-to-center spacing ratio of 2.5. A mixture of standing-traveling wave pattern was induced in the in-line (IL) vibration, while the cross-flow (CF) vibration displayed a standing-wave characteristic. The ninth vibration mode prominently occurred in both IL and CF directions, along with competition between multiple modes. Proximity effects from the neighboring cylinder caused the primary frequency to be consistent between IL and CF vibrations for each cylinder, deviating from the IL to CF ratio of 2:1 in isolated cylinder conditions. Repulsive mean lift coefficients were observed in both stationary and vibrating conditions for the two cylinders due to asymmetrical vortex shedding in this small gap. Comparatively, lift and drag coefficients were notably increased in the vibrating condition, albeit with a lower vortex shedding frequency. Positive energy transfer was predominantly excited along the span via vortex shedding from the cylinder itself and the neighboring one, leading to increasing lower-mode vibration amplitudes. The flip-flopping (FF) wake pattern was excited in the stationary and vibrating cylinders, causing spanwise vortex dislocations and wake transition over time, with the FF pattern being more regular in the stationary cylinder case. [ABSTRACT FROM AUTHOR]

• A partitioned fluid-structure interaction (FSI) framework is developed. • The meshless Vector Form Intrinsic Finite Element (VFIFE) is innovatively used as a solid solver. • Various benchmarks involving vortex-induced vibration phenomena are studied with the new algorithm. • Strong adaptability and accuracy of the VFIFE method are proved by numerical results. • An experimental case of flow past flexible curtain in a water tank is investigated. The Vector Form Intrinsic Finite Element (VFIFE) is an advanced meshless Lagrangian structural solver. This study introduces a partitioned framework to integrate Arbitrary Lagrangian-Eulerian and VFIFE methods into fluid-structure interaction (FSI) problems featured by large structural displacements and deformations. The VFIFE method enables the FSI simulations with deformable structures due to the nature of Lagrangian particles, which is challenging for traditional computational fluid mechanics techniques. In addition, the VFIFE can be effectively equipped with the partitioned coupling schemes because of the versatility of governing equations. In this algorithm system, several matrix problems in finite element methods and mapping and interpolation in the fluid-structure interface can be avoided. The significant potential of this algorithm in tackling complex FSI problems is demonstrated through various benchmarks, encompassing scenarios like Taylor-Green vortex, flow over a rigid cylinder (Re = 40 ∼ 200), forced vibration of a rigid cylinder, vortex-induced vibration (VIV) of an elastically mounted cylinder, and VIV of a rigid cylinder with an attached flexible cantilever beam. Finally, an experiment on flow past a curtain in a water tank is conducted to further evaluate the precision and stability of the current coupling strategy in three dimensions, demonstrating the feasibility of such methods in flexible structures. [ABSTRACT FROM AUTHOR]

We investigate the effectiveness of a vibration absorber on the vortex-induced vibration response of turbine blades during the frequency lock-in phase. A reduced-order model of a turbine blade and van der Pol oscillator is used to represent the fluid–blade interaction caused by the vortex shedding. A spring-mass-damper system is considered to model the vibration absorber. The advantage of the vibration absorber is demonstrated by simulating the nonlinear coupled four-degree-of-freedom aeroelastic system for the different sets of system parameters. We observe the dominance of a nonlinear vibration absorber over the linear vibration absorber only for the higher coupling parameter values. The analytical solution of the nonlinear coupled system is obtained through the method of multiple scales for the case of 1:1 internal resonance to identify the critical design parameters of the vibration absorber. We observe the high sensitivity of the system's frequency response to the distance of the vibration absorber from the elastic axis, along with the absorber's damping, stiffness, and mass. Finally, we perform a parametric analysis on the lock-in of the stability region to better understand the effect of the vibration absorber on the instability region. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In order to study the response law of vortex-induced vibration (VIV) of marine risers under the combined action of roughness and interference effects, and to reveal the coupling mechanism of roughness and interference effects on the riser, a VIV experiment of rough risers in tandem arrangement was conducted in a wave–current combined flume. The experiment characterized the risers' roughness by arranging different specifications of attachments on the surface of the risers. Three rough risers with different roughness and smooth risers were arranged in tandem arrangement, with the rough risers arranged downstream. The experimental results indicate that the suppression of the attachments on the downstream risers' vibration are more significant both in the CF and IL directions as the reduced velocity increases. For the downstream riser, the amplitude response of rough riser is more significantly weakened compared with the smooth one at high reduced velocity. For the upstream risers, changes in the roughness and spacing ratio have an impact on their 'lock-in' region. When the roughness of downstream risers is relatively large (0.1300) and the spacing between risers is small (S/D=4.0), the reduced velocity range of 'lock-in' region in the CF direction of upstream risers is obviously expanded, and the displacement in the 'lock-in' region is severer. [ABSTRACT FROM AUTHOR]

Based on the flow induced motion energy conversion system, the combined triangular prisms with the section form and stiffness as variables to evaluate the amplitude, frequency and other indicators was studied. The combined triangular prisms were selected for model test, as well as the influence of arrangement and stiffness on the combined triangular prisms were studied by changing the arrangement of the prisms and system stiffness. The aim is to explore the optimal condition for flow induced motion of the three triangular prisms in different arrangements, and to expand ideas for subsequent research on flow induced motion of multiple oscillators. The experimental results show that all the combined triangular prisms have good performance with different stiffness. Both the motion of type I prism and type III prism perform typical vortex induced vibration with the increase of flow velocity, the type I prism has the best performance. [ABSTRACT FROM AUTHOR]

Design load and vibration for parked conditions are gaining in importance for large-scale modern wind turbines with increasing flexibility, especially edgewise vibration when the blade is at a high angle of attack. In this work, flow-induced vibration of the wind turbine airfoil at 90 degrees of attack angle is studied with the fluid-structure interaction (FSI) simulation. The unsteady aerodynamic force due to flow separation and vortex shedding at the high angle of attack causes the chordwise vibration of the airfoil. When the vortex shedding frequency f v gets close to the chordwise natural frequency f n of the airfoil, vortex-induced vibration (VIV) of high amplitude occurs accompanied with the frequency lock-in phenomenon. In the post lock-in regime, it is found that period-3 and torus bifurcation occur successively and the vibration response becomes aperiodic. Dynamic mode decomposition(DMD) technique is used to investigate the mechanism of bifurcation from the perspective of energy balance, through analyzing the vorticity field in the wake and pressure distribution on the airfoil surface. For the certain incoming velocity in the post lock-in regime, since the frequency of the DMD mode f = 2 f v / 3 is close to the natural frequency f n , both the vibration of frequency 2 f v / 3 and f v get excited, leading to the onset of bifurcation. The Lissajou curves are obtained through reconstructing the transient pressure of each DMD mode, which indicates that energy transfer mainly exists in modes f = f v . In addition, the reconstructed Lissajou curves based on the leading DMD modes agree well with the original time-domain Lissajou curves. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of the top-end dynamic boundary of risers caused by floater motions on their vortex-induced vibration (VIV) characteristics, a combined model comprising a buoyancy can with a relatively simple structural form and a riser is taken as the research object in the present study. The aspect ratios of the buoyancy can and the riser model are 5.37 and 250, respectively. A set of experimental devices is designed to support the VIV test of the riser with a dynamic boundary stimulating the vortex-induced motion (VIM) of the buoyancy can under different uniform flow and regular wave conditions. Several data processing methods are applied in the model test, i.e., mode superposition, Euler angle conversion, band pass filter, fast Fourier transform, and wavelet transform. Based on the testing results, the effect of low-frequency VIM on the high-frequency VIV of the riser is discussed in relation to a single current, a single wave, and a combined wave and current. It is found that the coupling effect of VIM on the riser VIV presents certain orthogonal features at low current velocities. The effect of the cross-flow VIM component on VIV is far more prominent than that of its counterpart, the in-line VIM, with increasing flow velocity. The VIM in the combined wave–current condition significantly enhances the modulation of vibration amplitude and frequency, resulting in larger fluctuation peaks of vibration response and further increasing the risk of VIV fatigue. [ABSTRACT FROM AUTHOR]

An electromagnetic vibro-impact nonlinear energy sink (EM-VINES) is proposed in the application of vortex-induced vibration, for both purpose of vibration suppression and energy harvesting. The considered system consists of a cylinder-like bluff body subject to an oncoming flow, coupled to a magnet attachment moving in coil of gap enclosure. The fluid–structure interaction is treated using the classical Van der Pol oscillator model, and the non-smooth dynamics is formulated in a measure differential complementarity problem adapted with a Moreau–Jean time integration scheme. Comprehensive analyses are then conducted concerning the targeted energy transfer mechanism, as well as the internal competition of the energy flow. A performance indicator is defined over the lock-in region, to obtain the optimal balance between vibration suppression and energy harvesting. It is found that when the system is working in a strongly modulated regime with less than 2 impacts per cycle, a fast-scale targeted energy transfer could be activated over the whole lock-in region, making the EM-VINES behave efficiently for both vibration suppression and energy harvesting in the application of vortex-induced vibrations. [ABSTRACT FROM AUTHOR]

Harvesting energy from flow using vortex-induced vibration (VIV) piezoelectric transducers has gained significant attention in recent decades due to their advantages, such as simple structure, blade-less layout, and low maintenance costs. However, most existing studies have focused on designing and analyzing a single piezoelectric energy harvester (PEH), without investigating the fluid-structure interaction and coupling of multiple PEH arrays. Here, we conducted an experimental study using a 2 × 2 PEH array to investigate its dynamic response under different wind speeds and spacings. Results show that the output voltage of the PEH array increases as the vertical spacing decreases, and the maximum average output voltage of 20.6 V per PEH is obtained when the minimum vertical spacing, maximum horizontal spacing, and resonance wind speed conditions are met. Compared to a single PEH, the 2 × 2 array arrangement increases the average output voltage by up to 168%. Additionally, the average output power under the resistance of 1 MΩ increases by 629% to 4.3×10−4 W per PEH, and the maximum output power increases by 792% to 5.3×10−4. Experiments indicate that the vortex shedding coupling can induce higher vibration in a well-defined array, which paves a new way for developing bladeless wind farms. [ABSTRACT FROM AUTHOR]

The oscillation of a cylinder, which is excited by steady fluid flow, is investigated. Regarding the nonlinearity of real practical structures like marine risers and the stay cable of a long-span bridge, the dynamic behavior of a circular cylinder is described using two nonlinear equations, and the aerodynamic force performance of the wake flow is expressed by the wake oscillator equation. Unlike previous studies, in the present investigation, attention is focused on coupling the wake oscillator equations, considering quadratic terms. Following this approach, the cylinder's mixed in-line and crossflow vortex-induced vibrations (VIV) are accurately modeled. Experimental coefficients are corrected using previous credible experimental studies and the effects of changing coefficients of the VIV parameters are studied in the sub-critical Reynolds number range of about 2×103–5×104. The oscillating amplitude calculated by the present model is close to that of the experiment. The present model has a lower relative error compared to the previous model. The model presented can predict the lock-in range with greater accuracy for bluff bodies near the plate than previous models. Moreover, the present model successfully predicts the moving trajectories of a circular cylinder under VIV in a figure-of-eight shape. [ABSTRACT FROM AUTHOR]

In recent years, there have been numerous failures in submarine power cables caused by seawater erosion. Vortex-induced vibration is the main cause of fatigue damage or breakage in submarine power cables. In this paper, model similarity theory was introduced into finite element modeling of submarine power cable for the first time, which dramatically reduced the amount of model calculation. The resonance frequency, amplitude and corresponding flow rate were determined and the stress distribution was analyzed of submarine power cable with different length-to-diameter ratios by acoustics modal and harmonic response. A relationship equation between fatigue life and length-to-diameter ratio was established. The results show that the resonance frequency ranges from 2.651 to 6.633 Hz and the resonance amplitude was 0.64 times the cable diameter when the 110 kV submarine power cable had a length-to-diameter ratio between 70 and 110. The fatigue life was a power function of different length-to-diameter ratios. This research overcomes the difficulties of conducting physical tests and full-scale modeling of vortex-induced vibration of submarine power cable. It provides a viable method and data support for the characterization and fatigue analysis of vortex-induced vibration of submarine power cable.

Steel tube members with high slenderness ratios in transmission towers are susceptible to vortex-induced vibration (VIV), which can lead to fatigue damage once the vibration amplitude exceeds a certain threshold. This study proposes a VIV prediction framework for transmission tower steel tube members with semi-rigid constraints, based on the developed generalized wake oscillator model (GWOM). Firstly, the GWOM is established by coupling the nonlinear Van der Pol oscillator with the Euler–Bernoulli beam equation and incorporating semi-rigid boundary conditions. Meanwhile, the identification methods for the rotational stiffness and empirical parameters in the GWOM are presented, respectively. Second, a numerical solution scheme of the GWOM is derived based on the central difference method, and then a VIV prediction framework for steel tube members with arbitrary structural configuration is established. Comparisons with published experiments demonstrate that the proposed GWOM-based prediction framework has a promising accuracy in estimating the lock-in range and maximum VIV amplitude. The influence of semi-rigid constraints on the VIV of steel tube members is mainly manifested in the critical wind speed, but it has little effect on the amplitude branch. The proposed framework provides an efficient and cost–effective alternative to traditional experimental methods and computational fluid dynamics CFD simulations for predicting the VIV of steel tube members in transmission towers. [ABSTRACT FROM AUTHOR]

Vortex-induced vibration (VIV) of long-span bridges can be of large amplitude, which can influence serviceability. Therefore, it is important to predict the response of vortex-induced vibration to aid the management of long-span bridges. A novel data-driven model is proposed to predict the time history of the dynamic response of VIV events. Specifically, the proposed model consists of gated recurrent unit (GRU) neural networks and the Newmark-beta method. GRU neural networks can perform accurate sequential prediction, and the Newmark-beta method can complement the physical meaning of the middle output of the proposed model. To aid the accurate prediction of the amplitude of VIV events, the proposed model employs weighted mean square error as the loss function, which can put more emphasis on the amplitude. The proposed model is validated on measured VIV events of a long-span suspension bridge. The weighted mean absolute percentage error and Pearson correlation coefficient of the trained model indicate the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

In this study, an L-beam vortex-induced vibration piezoelectric energy harvester with interference step is proposed. The experimental results show that the interference step can broaden the effective wind speed bandwidth in the second resonance region of the energy harvester and increase its energy output amplitude significantly. When the load resistance is 90 kΩ, the effective wind speed bandwidth in the second resonance region of the energy harvester can be expanded by a maximum of more than 200%, and the peak output power can be increased by a maximum of 291% by adjusting the position, width and height of the step. [ABSTRACT FROM AUTHOR]

Offshore pipelines of different diameters are often seen in piggyback arrangements in close proximity. Under the effects of external flows, the pipelines may experience vibration. Reliable prediction of the vibration amplitudes is important for the design and operation of these structures. In the present study, the effect of the position angle (α) and gap ratio (G/D) of a piggyback pipeline on the amplitude of 1DOF vortex-induced vibration (VIV) was investigated experimentally in a wind tunnel. The diameter ratio d/D of the two cylinders was 0.5. Five position angles, namely, α = 0°, 45°, 90°, 135°, and 180°, and six gap ratios at each angle, G/D = 0, 0.1, 0.2, 0.3, 0.4, 0.5, were tested. It was found that both α and G/D affected the amplitude of vibrations significantly. For all gap ratios, the amplitude of vibrations increased from α = 0° to α = 90° and then decreased to a minimum value around α = 135°. The maximum amplitude occurred around α = 90° when G/D = 0, and the minimum occurred around α = 135°, when G/D = 0.2–0.3. At other position angles, the vibration amplitude was less sensitive to G/D, especially when the latter was between 0.1 and 0.4. These results verified those obtained using numerical methods and are invaluable to engineers when designing offshore piggyback pipelines. [ABSTRACT FROM AUTHOR]

This paper proposes a novel wake-induced vibration (WIV)-based energy harvesting system consisting of two bluff bodies. An inverted C-shaped bluff body is stationary installed at the upstream position to generate an interference wake street, and a cylinder bluff body equipped with a transducer is elastically suspended at the downstream position to harness WIV energy. The hydrodynamics and energy harvesting (EH) performance of the proposed system are investigated via experimental studies. The reduced velocity (U*) ranging from 2 to 14 (the corresponding Reynolds number ranging from 15100 to 106200) is considered in the present study. It is found that the wake generated by the inverted C-shaped bluff body significantly affects the EH performance. Enlarging the opening angle (α) of the C-shaped bluff body increases the vibration amplitude of the downstream cylinder, thereby increasing the harvested power. When the spacing (L) between two bluff bodies is two times the cylinder diameter (D), the wake-induced vibration (WIV) mode is observed, while the combined WIV and wake galloping (WG) mode occurs when α is 150°, and L equals 3D or 4D. The average drag coefficient becomes negative when L is 2D, 3D, or 4D. By carefully configuring a C-shaped bluff body, the wake generated by it can bring an augmenting effect on the vibration of the downstream EH cylinder. For example, the RMS power output of the proposed EH system reaches a maximum of 0.31 W at U* = 8 and L = 4D, which is 300% greater than that of its traditional counterpart. Furthermore, after a number of case studies, it is identified that the proposed EH system can achieve the best performance when α is 150° and L = 2D. [ABSTRACT FROM AUTHOR]

A vortex-induced vibration (VIV) experiment of rough risers with coupling interference effect under a side-by-side arrangement was carried out in a wave-current combined flume. The roughness of the riser was characterized by arranging different specifications of surface attachments on the surface of the riser. Rough risers with three different roughnesses were arranged side by side with smooth risers to explore the VIV response of the riser under the combined action of roughness and interference effect, and to reveal the coupling mechanism between roughness and interference effect. The experimental results show that, compared with that of a smooth riser, the VIV of a rough riser under the coupling interference effect has a wider "lock-in" region, and the displacement decreases more significantly at a high reduced velocity, which is more likely to excite higher-order modes and frequency responses. In addition, the displacement response and frequency response of the smooth riser are not significantly affected by wake interference from the rough riser, which is caused by the decrease of the wake region due to the delay of the boundary layer separation point of the rough riser. [ABSTRACT FROM AUTHOR]

The Π -shaped open section girder is a very common section, which has been widely used in the construction of modern bridges. However, compared with a streamlined box girder, it is easy to cause vortex-induced vibration (VIV) in bridges due to its bluff section shape and poor aerodynamic stability. In this paper, a typical open section with a height–width ratio of 10:1 is taken as the research object. Through wind tunnel tests and numerical simulation technology, the time-history data of VIV of the Π -shaped section are obtained. By selecting three different neural network models to establish the relationship between external parameters (wind attack angle, wind speed, turbulence) and structural response parameters (the onset wind speed of VIV, the length of the lock-in interval). After comparing different machine learning methods, the most suitable machine learning model is selected to predict the VIV response characteristics of the main girder. The research results show that the typical open section has a serious VIV phenomenon. The BP neural network model has the best performance in predicting the VIV performance of the open section in terms of calculation speed, prediction accuracy and solving nonlinear adaptability. At the same time, it is found that different characteristic parameters of the incoming wind field have different influences on the prediction results of the VIV response. Among them, the wind attack angle is the key parameter that affects the onset wind speed of VIV, but the turbulence intensity has a greater impact on the maximum amplitude of VIV. At the same time, the optimized BP model can predict the characteristic parameters of VIV response under unknown wind fields. This paper provides a new idea to study the effect of different incoming flow parameters on the performance of section VIV and further improves people's understanding of VIV system. [ABSTRACT FROM AUTHOR]

AbstractThe heat transfer and hydrodynamic properties of two rigid cylinders in series with fluid disturbance at the laminar flow under vortex-induced vibration were studied numerically. The six DOF model was chosen and combined with user-defined functions (UDF) to seek a solution for the cylindrical equations of motion. The coupled calculation between fluid flow and rigid body motion was realized by combining the dynamic mesh technique. The effects of two types of motion conditions of the upstream cylinder, i.e. fixed (referred to as model A) and with two degrees-of-freedom (referred to as model B), on the flow field and heat transfer of the downstream cylinder with two degrees-of-freedom were investigated. The numerical results showed that in the reduced velocity (Ur) range considered in this work, the heat transfer and motion conditions of the downstream cylinder were subjected to the self-shedding vortices and the shedding vortices of the upstream cylinder. The comparison of models A and B at Ur = 4 and Ur = 5, respectively, displayed that the force frequency of the downstream cylinder was close to the natural frequency when it was impacted by the tail vortices shedding of the upstream cylinder and the self-shedding vortices. This resulted in the maximum transverse amplitude and strongest heat transfer of the downstream cylinder. [ABSTRACT FROM AUTHOR]

To investigate the vortex-induced vibration (VIV) of a flexible cable in the uniform flow, experiments were conducted using a flexible cable with an external diameter of 80mm and a length of 10.48m in the wind tunnel. The characteristics of multi-modal VIV, time-frequency and traveling wave behavior of the flexible cable were analyzed. Moreover, the effects of twist direction, diameter and the single/double helical wire on the VIV characteristics of the flexible cable were investigated. It is found that the flexible cable experiences single and multi-modal VIVs in uniform flow at different incoming wind speeds, respectively. For the multi-modal VIV of the flexible cable, the vibration over the time history is dominated by two adjacent modal frequencies and shows a phenomenon of beat vibration. The multi-modal VIV responses of the flexible cable show a mix of standing and traveling wave behaviors, in which the effects of standing wave are more pronounced near both ends and the effects of traveling wave are more dominant in the middle region of the flexible cable. The twist direction of the helical wire has little effect on the VIV responses of the flexible cable. The VIV amplitudes of the flexible cable can be reduced by a single helical wire. With the diameter of the helical wire increases, the suppression effects of the single or double helical wire on the VIV of the flexible cable can be improved. Particularly, the double helical wire with diameter 0.10D can effectively suppress the VIV of the flexible cable. [ABSTRACT FROM AUTHOR]

Energy harvesting from Vortex-Induced Vibration (VIV) presents a promising avenue for renewable energy generation by harnessing the kinetic energy of fluid flows through innovative technologies. Despite the increasing interest in VIV energy harvesting, there is a need for a systematic evaluation of the existing literature to understand the research trends, key contributors and emerging areas of focus. A bibliometric analysis offers a quantitative approach to address this gap, providing valuable insights into the evolution and dynamics of research on energy harvesting from VIV. The analysis employs VOSviewer software to analyze publication data retrieved from Scopus, focusing on publication trends, top authors, subject area, top citation, popular keywords, co-authorship countries' collaboration and network mapping based on citation by country. By examining publication patterns, citation counts and collaboration networks, this study aims to uncover underlying patterns and identify critical factors driving research in this field. The bibliometric analysis reveals a significant upward trend in research activity, with a notable increase in publications from recent years, indicating growing interest and recognition of VIV energy harvesting. In conclusion, this bibliometric analysis provides valuable insights into the research trends, key contributors and collaborative networks in energy harvesting from VIV. The findings guide for both academic and industrial, facilitating informed decision-making and driving progress toward sustainable energy solutions. This study also lays the groundwork for future research directions and interdisciplinary collaborations aimed at maximizing the potential of VIV energy harvesting for renewable energy generation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve a vibrational power generator using a magnetostrictive material, i.e., Iron-gallium alloy, and flow-induced vibration of a cantilevered cylinder, a fixed splitter plate was installed behind a cantilevered circular cylinder. Effects of a gap between a splitter plate and a circular cylinder on the performance of the response amplitude, the power of the flow-induced vibrational power generator and the vortex shedding frequency were investigated through wind tunnel experiments. Flow visualizations around a circular cylinder were also conducted by a smoke-wire method using a high-speed camera. The test models had a span length L of 200 mm, 300 mm and 400 mm. The diameter of a circular cylinder D of 40 mm. A splitter plate with a length of 400 mm and a thickness of 2 mm was installed behind the center of the model with a gap G varied from 8 to 104 mm. For a small gap ratio of G/D ≤ 0.6, galloping vibration occurred. From the smoke wire visualization, it was related that the upstream flow to the cylinder went along a side surface of the cylinder and the inner circulatory flow was generated near the gap. As a result, the accelerated gap-flow occurred and the negative pressure was generated periodically on the upper or lower side wall of the cylinder. For a large gap ratio of G/D ≥ 1.2, galloping vibration did not occur, and the response amplitude became similar to the circular cylinder without a splitter plate. The power generation of a circular cylinder having L = 200 mm with G/D = 0.2 was largest. However, the onset wind velocity of vibration was larger than that of the other cylinders and gaps.

To analyze the dynamic response of a rigid M-shaped jumper subjected to combined internal and external flows, a one-way coupled fluid–structure interaction process is applied. First, CFD simulations are conducted separately for the internal and external fluid domains. The pressure histories on the inner and outer walls are exported and loaded into the finite element model using inverse distance interpolation. Then, FEA is performed to determine the dynamic response, followed by a fatigue assessment based on the obtained stress data. The displacement, acceleration, and stress distribution along the M-shaped jumper are obtained. External flow velocity dominates the displacements, while internal flow velocity dominates the vibrations and stresses. The structural response to the combined effect of internal and external flows, plus the response to gravity alone, equals the sum of the structural responses to internal flow alone and external flow alone. Fatigue damage is calculated for the bend exhibiting the most intense vibration and higher stress levels, and the locations with significant damage correspond to areas with high maximum von Mises stress. This paper aims to evaluate multiple flow fields acting simultaneously on subsea pipelines and to identify the main factors that provide valuable information for their design, monitoring, and maintenance.

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vortex-induced vibration is a typical nonlinear fluid–structure interaction phenomenon. Significant challenges to high-precision prediction by the prevalent methods rely on three complex nonlinear dynamic behaviors: nonlinear evolution (NE), vibration peak deviating from the resonance (PD), and nonlinear hysteresis. Although the semi-empirical model is a theoretical and efficient manner, it is difficult to accurately predict the above nonlinear phenomena due to the incomplete mathematical expressions and uncertain parameters. In this paper, a data-knowledge-driven (DKD) augmentation method is proposed to modify the typical wake oscillator model. A comprehensive analysis is first conducted for the effect of the potential aerodynamic damping terms. Motivated by the above analysis, a delay damping term is proposed which contributes to the NE and PD phenomenon by affecting the growth rate of the flow frequency and triggers the mode transition of the coupled system. With these physical understandings, a new model architecture is constructed by combining the delay damping and the Rayleigh damping. Besides, experimental data are utilized to identify the empirical parameters of the model by the ensemble Kalman filter data assimilation technique. The results indicate that the DKD model (marked as Van-Delay-Rayleigh) can accurately compute these nonlinear behaviors for 25 different cylinders. Compared with the original model, the prediction accuracy of the DKD model is improved by 2–5 times. It also shows the generalization capability with various mass-damping parameters, which can reduce the number of wind tunnel tests by 70%. [ABSTRACT FROM AUTHOR]

As a high-rise structure, the tower of a suspension bridge has low stiffness due to the lack of cable system constraints when it is self-supporting. Wind-induced vibration is one of the key factors in design and construction. In this paper, the wind tunnel test of the bridge tower aeroelastic model is carried out in two different flow fields, and the wind vibration response under a self-supporting state is systematically studied. Meanwhile, numerical simulation of the unsteady flow field around the tower section is carried out, and the dynamic modal decomposition (DMD) method is used to study the modal frequency of the flow field, the surface pressure of the section, flow field reconstruction error, and the stability of the flow field around tower section is discussed. The results show that in the self-supporting state, the displacement of the tower top presents a quadratic curve relationship with the wind speed, and no galloping phenomenon occurs under the test wind speed. However, in the uniform flow, when the wind attack angle is 90°, the bridge tower has an obvious vortex-induced vibration (VIV) phenomenon. After decomposing the flow field by the DMD method, it is found that there is strong aerodynamic interference between the double rectangular column sections, the first seven orders of modal energy play a major role in the flow field, and when the main modal energy accounts for more than 90%, the reconstruction can realize the accurate restoration of the information such as the surface pressure. For the complex flow field structure, it shows that the method can more accurately identify the coherent structure and background part in the unsteady flow field. This paper provides an idea for future research on the characteristics of the flow field around complex sections and helps to further improve the understanding of the VIV mechanism. [ABSTRACT FROM AUTHOR]

The increasing number of suspension bridges has led to designs favoring greater length and flexibility, resulting in a common problem of vortex-induced vibration. While vortex-induced vibration typically does not cause structural damage, it diminishes the bridge's fatigue resistance and has a detrimental impact on ride comfort. Additionally, this study introduces a road–bridge–vehicle vibration model, proposing an evaluation method for assessing ride comfort during vortex-induced vibrations in long-span bridges. This method features simplified modeling and swift calculations, circumventing the need for intricate finite element modeling and iterative solving. Furthermore, it evaluates ride comfort for vehicles crossing a prototype long-span suspension bridge using the Overall Vibration Total Value (OVTV) and Motion Sickness Incidence (MSI) criteria. This study also analyzes the influence of various parameters on OVTV and MSI, including vehicle speed, road grade, vortex-induced vibration frequency, and amplitude. It establishes a reference limit for vortex-induced vibration amplitude based on OVTV and MSI values. Moreover, the study substantiates that, within the context of vortex-induced vibration, the MSI value is more suitable for evaluating driving comfort compared to the OVTV. [ABSTRACT FROM AUTHOR]

Based on the slicing method and overlapping grid method, the bidirectional and sequential coupling of the fluid domain and riser structure is realized by UDF programming. A numerical model of vortex-solid coupling is constructed to study vortex-induced vibration characteristics of risers with different velocity ratios and different oscillation frequencies under the effect of superimposed oscillating flow. With the increase of the velocity ratio, a higher order formation appeared in the transverse vibration envelope of the riser. Meanwhile, with the increase of oscillation frequency, the vertical tube vibration envelope changed from "symmetrical up and down" to "wide up and narrow down". There is an obvious process of "establishment", "locking" and "decay" in the transverse-flow displacement of the riser to dimensionless, and the proportion of the "locking" phase increases gradually with the flow rate ratio, changing from 0.50 to 0.62. The effect of the oscillation frequency of the superimposed flow on the proportion of the "locked" stage is not evident. When the oscillation frequency is 0.25f1, the proportion of the "locked" stage of the riser reaches 50%. [ABSTRACT FROM AUTHOR]