Vortex-induced Vibration Response Research Articles

Experimental and numerical study on vibration response, VIV mechanism and aerostatic coefficients of triple-separated decks under different vertical distances

In this study, aerodynamic interference effects (AIE) on the vibration response, aerostatic coefficient (AC) and vortex-induced vibration (VIV) mechanism of the triple-separated decks under different incoming wind directions and vertical distances were investigated via wind tunnel tests and numerical simulations, respectively. The test results show that the AIE increases the displacement of VIV, and the VIV responses reaches maximum value under S/H = −1.0 (S is the vertical distance between the centers of RB and HB decks, and H is the height of RB deck) when the RB deck is on the windward side (the maximum displacements of VIV are 193.86% and 37.30% higher than the case of single RB deck and S/H = 0.0, respectively). The pressure distribution and flow structure show that the scale of vortex that alternately shed off from the tail of the deck becomes stronger and the fluctuating pressure coefficient increases under AIE, which increase the VIV amplitude of the RB deck and cause the VIV of HB decks. The experimental and numerical results indicated that the aerostatic coefficients (AC) of the leeward girder are more affected by the AIE. The interference factor (IF) of drag coefficient (CD) is far less than 1.0 under the case of F-5 (S/H = 0.0).

Experimental investigation on hydrodynamic characteristics of water intake riser undergoing vortex-induced vibration in uniform flow

With the development of ocean engineering, freely hanging water intake riser (WIR) has aroused widespread interests. The WIR with one free end would be easier to deflect remarkably, along with more complex vortex-induced vibration (VIV) responses and hydrodynamic forces. To elucidate the VIV characteristics of WIR under uniform flow, a series of VIV experiments for a scaled WIR model are carried out. Then a hydrodynamic identification method for VIV along with large offset is developed. The response and hydrodynamic characteristics of the WIR in cross-flow (CF) and in-line (IL) directions are further analyzed. Results indicate that VIV displacements with higher exciting modes are unstable when uniform flow velocity gets large. The IL-to-CF dominant frequency ratio of VIV is found to be 1.0, not 2.0 in conventional VIV knowledge and the IL harmonic at nearly twice the dominant CF frequency is observed more complex for flow velocity greater than 0.3 m/s. The vortex-induced force coefficients are found to be time-varying. Moreover, it is found that within the spectrum of Reynolds number from 2 × 103 to 1.1 × 104, the drag coefficient distribution changes along the WIR model, and the average drag coefficient is in range of 1.0–1.5, which is slightly smaller than the results predicted by the other published empirical formulae.

A study on vortex-induced vibration of a long flexible catenary cable in perpendicular flow

In this paper, a numerical model based on Euler-Bernoulli beam theory and a single van der Pol wake oscillator model is proposed to study the vortex-induced vibration of a long flexible catenary cable with a low mass ratio. The wake model uses only one oscillator to describe the in-line and cross-flow vibration with consideration of their nonlinear coupling. An experiment on a flexible cable model in perpendicular flow is carried out to validate the proposed numerical model. Numerical results and experimental measurements are compared on the vortex-induced vibration responses including the maximum amplitude, axial tension, and vibration frequency. A sensitivity analysis of the parameters used in the numerical model has been carried out. Numerical simulations by the proposed numerical model with properly selected parameters have demonstrated that the vibration frequency and the axial tension can be well predicted, and the variation of the vibration amplitudes can also be properly captured. The lock-in phenomena and the axial tension variation of the long flexible catenary cable in perpendicular flow have been carefully studied both numerically and experimentally.

Frequency lock-in control and mitigation of nonlinear vortex-induced vibrations of an airfoil structure using a conserved-mass linear vibration absorber

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.

Passively Enhanced Vortex-Induced Vibration Response of Side-by-Side Cylinders in Turbulent Flow

Passively Enhanced Vortex-Induced Vibration Response of Side-by-Side Cylinders in Turbulent Flow

Correlation and modal analysis techniques for the study of the VIV response of a twin-box deck based on 3D LES simulations

AbstractTwin-box decks are prone to vortex-induced vibration (VIV) at moderate wind speeds, and previous studies have shown a complex interplay between the flow and the two parallel box girders. OpenFOAM is used to model the aerodynamic and aeroelastic responses of the twin-box deck of the Stonecutters Bridge by means of 3D LES simulations. Two cases are thoroughly analysed under smooth incoming flow: (i) static deck and ii) heave peak amplitude response at VIV excitation. The computational data provided by the CFD simulations have been exploited aiming at better understanding the complex aerodynamic and aeroelastic phenomena taking place. First, spanwise correlation analyses are applied to understand the level of organisation of the forcing flow actions, and identify the regions of the deck affected by different flow structures. Second, three different mode decomposition techniques (POD, SPOD and DMD) are applied to the time-dependent pressure distributions, revealing the pivotal role played by the leeward box in the twin-box deck response under wind action. The modal analyses are of utmost interest in the development of Reduced Order Models (ROM) for the VIV response of twin-box long-span bridges.

Numerical investigation on vortex-induced vibration of catenary riser conveying fluid under top-end heave excitation

ABSTRACT Due to the catenary shape of steel catenary risers (SCR), the heave motion of the floating platform can generate an equivalent oscillatory flow field and excite the vortex-induced vibration (VIV) of SCR. Internal flow conveyed by SCR further complicates the VIV response. A semi-empirical model is improved to simulate the VIV of SCR with internal flow under top-end heave excitation. VIV characteristics such as displacement temporal–spatial distribution and amplitude spectra spatial distribution are analysed and the fatigue damage is calculated. The effects of heave period, heave amplitude, internal flow volumetric flow rate and internal flow density on VIV of SCR are discussed. The heave excitation with short period or large amplitude tends to excite high-order-mode response and enlarge the fatigue damage. The VIV response becomes less regular and the fatigue damage is reduced when the internal flow volumetric flow rate or density increases.

Energy extraction and optimization studies on vortex-induced vibration of the elastically mounted rigid cylinder using wake oscillator model

The vortex-induced vibration (VIV) response of an elastically mounted rigid cylinder from the standpoint of energy harvesting is analyzed with the aid of the wake oscillator model (WOM). A model of an elastically mounted rigid cylinder free to oscillate in the in-line (IL) and cross-flow (CF) directions subjected to different uniform flow velocities is considered and its responses under different mass ratios are predicted using the modified wake oscillator model. For modeling structure motion, the dynamic equilibrium equation, and for modeling the fluid part, the Van der Pol wake oscillator is utilized and they are coupled together to get the response in IL and CF directions. A comparative study is performed between the numerical and the experimental results and they are found to be in good agreement. The study is then probed into the scope of energy extraction from VIV which will presumably throw light into the development of VIV-based energy harvesting methods which is a potential future hope for the renewable energy sector. Parametric optimization study is carried out to determine the maximum harnessable energy from VIV. The response of the cylinder for the optimal parametric combination is analyzed in the time and frequency domain. It is observed that damping and reduced velocity play a crucial role in the energy extraction.

A Data-Driven Model for Predictive Modeling of Vortex-Induced Vibrations of a Long-Span Bridge

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.

Analysis of the vortex-induced vibration response characteristics of riser under the soft suspension evacuation condition

This paper establishes a nonlinear dynamic model for a suspended riser under the condition of considering realistic configurations, based on the principles of virtual work and Hamilton's variational principle. The nonlinearity of the model is manifested by considering vortex-induced vibration in the cross flow (CF) and in-line (IL) directions, as well as large deformations, taking into account the variable diameter of the riser in the compliant riser system. The model is discretized using the finite element method and solved using the Newmark-β method. Experimental validation is conducted to verify the effectiveness of the model. Utilizing the parameters of a riser in a well in the South China Sea, the paper explores the influence of different environmental and structural parameters on the VIV response characteristics of a compliant riser. Results show that the vibration frequency is controlled by both the bare tube and buoyant block when the buoyant block coverage rate is 25%, which can significantly inhibit VIV. With the increase of flow velocity, the VIV energy jumps from low order to high order, and the riser mode also transitions from low order to high order. The increase in suspension length transfers the vibration energy from high to low frequency, thus realizing energy transition and mode shape transformation. With the increase in LMRP weight, the vibration and natural frequencies of the riser increase synchronously, the vibration amplitude decreases, and the mode shape remains unchanged.

Numerical investigation on the effect of bionic fish swimming on the vortex-induced vibration of a tandemly arranged circular cylinder

The effect of bionic fish swimming on the vortex-induced vibration (VIV) of a circular cylinder arranged in tandem at a low Reynolds number of 150 is numerically investigated in this work. The bionic fish placed upstream of the cylinder with gap ratios of 1, 3, and 5 and that located downstream of the cylinder with gap ratios of 3 and 5 are examined in the simulations that were carried out in the reduced velocity range of Ur = 2–15. It is found that both the gap ratio and the reduced velocity have a significant influence on the VIV response and wake flow structure. When the bionic fish is placed upstream, the maximum response amplitude of the downstream cylinder is much greater than that of an isolated one. Two flow regimes are identified in terms of the shear layer reattachment, i.e., the continuous reattachment and the alternate reattachment. Comparing the vortex shedding frequencies of the cylinder and the swimming fish, it is found that the frequency of the cylinder is always locked in the fish swimming frequency, and multiple frequencies occur at Ur = 5. When the bionic fish is arranged downstream, four flow regimes are observed, including the extended-body, continuous reattachment, alternate attachment, and co-shedding regimes. Furthermore, the time-mean energy transfer coefficient of the cylinder is considerably higher at Ur = 5 than that when the fish is placed upstream of the cylinder.

Experimental investigation on the vortex-induced vibration response of a lazy-wave flexible riser filled with different fluid media

Experimental investigation on the vortex-induced vibration response of a lazy-wave flexible riser filled with different fluid media

Simulation analysis of flow field and vortex-induced vibration characteristics of submarine cable under single/parallel-laying mode

Due to the long-term erosion of current, the submarine cable buried on the seabed surface easily causes fatigue damage to the lead sheath, which gradually progresses with time. In this paper, a two-dimensional spring-damping vortex vibration model is established considering the effect of transverse flow and in-line flow. The vortex-induced vibration response of suspended submarine cables under the influence of different parameters is simulated by using the slice method based on nested grids. The simulation model is used to simulate the flow field characteristics and vortex-induced vibration response of submarine cables under single laying and parallel laying conditions. The fluid-solid coupling mechanism between fluid and structure and the interaction law of parallel laying submarine cables are analyzed. Our study overcame the difficulty in testing the vortex-induced vibration of submarine cables and provided a viable method and empirical support for investigating the vortex-induced vibration properties of submarine cables and fatigue analysis.

Direct Measurements of Vortex-Induced Vibrations on a Horizontal Flexible Cylinder in Water

Abstract This work presents experimental results on vortex-induced vibration (VIV) of a horizontal cylinder with 2.69 m in length, 21 mm in diameter, and a mass ratio equal to 3.9. The experiments were carried out in a towing tank, where the flexible cylinder was towed under constant current profiles. Twenty reduced velocities were tested in a range of 1.75 < Vr < 15.79, corresponding to Reynolds numbers from 1000 to 10,000. The displacements were measured directly through a submerged optical system that simultaneously acquired the in-line and cross-flow movements of 18 reflective targets along the length. The extensive monitored section of the model enabled the application of a modal decomposition technique, which is a methodology that is still relatively unexplored through direct measurements. A comprehensive analysis was applied and the VIV responses related to amplitudes, frequencies, phase angles, and trajectories are shown and discussed in depth. The overall dynamics exhibits a multimodal response behavior, and the modal decomposition procedure has conclusively confirmed that the total amplitude comprises several modes vibrating at the dominant mode frequency. Root mean square values of response amplitude were up to 0.77D and 0.23D in the cross-flow and in-line directions, respectively. The cross-flow synchronization had a significant impact on the in-line excitation modes, and the trajectories showed coherence between motions.

A Simplified Approach to Recognize Vortex-Induced Vibration Response Using Machine Learning

The vortex-induced vibration (VIV) problem has been of critical concern for the wind-resistance of long-span bridges. Usually there are four types of approach for VIV studies: wind tunnel tests, field monitoring, computational fluid dynamics and mathematical models. However, traditional approaches have shown some limitations, such as high cost and low efficiency. In order to improve the efficiency and accuracy of VIV studies, this article has taken the VIV problem of a split three-box girder in a cable-stayed and cooperative suspension system bridge as an instance, and conducted a series of VIV wind tunnel tests. An approach based on machine learning is described that is able to serve as a complement to the wind tunnel tests. The proposed approach involves two steps: firstly, based on the dataset produced by wind tunnel tests, a clustering algorithm is introduced to separate the VIV signals automatically from other vibrations. Then, an artificial neural network is utilized to recognize the VIV response and aerodynamic force in the lock-in region directly. It is shown that the clustering algorithm can be a good tool for the recognition of VIV signals. Moreover, the proposed artificial neural network models show good ability for recognizing VIV amplitude and aerodynamic lift force.

Vortex-induced vibration response of the cylinder inspired by Terebridae

Vortex-induced Vibration (VIV) responses of the three-dimensional cylinders inspired by Terebridae are numerically investigated at the Reynolds number ranges of 0.8 × 104 ≤ Re ≤ 8.0 × 104. By Terebridae, we mean that inspired by its slender structural shape, and whether it can be used to improve the VIV suppression performance of the traditional structures. Three different cylinders are considered, including the smooth cylinder (T0), the Terebridae-inspired cylinder with four-start helical ribs (T1), and the Terebridae-inspired cylinder with six-start helical ribs (T2). The VIV responses of T1 and T2 is effectively suppressed, and T1 shows better suppression performance. The results show that the maximum cross-flow amplitude ratio of T1 is reduced by 70.7 % compared with that of T0, and the maximum in-line amplitude ratio of T1 is reduced by 85.7 % compared with that of T0. Compared with the maximum mean-drag coefficient of T0, it is reduced by 44.0 % for T1. In the high Reynolds number ranges, the galloping phenomenon does not occur for T1 and T2, and the relationship between the mean-drag coefficients of T0, T1 and T2 is Cd‾ (T2) > Cd‾ (T1) > Cd‾ (T0). It is found that the changes of Q-criterion vortex structure and wake flow play an important role in the VIV response. The Q-criterion vortex of T0 is a slightly curved linear shaped, and the Q-criterion vortices of T1 and T2 are break up. The three-dimensional geometry of the Terebridae-inspired cylinder undermines the correlation of vortex-shedding along the span. The wake flow of T0 can develop normally. The wake flow of T1 quickly rolls up after passing through the top separation point, and the reattachment of the wake vortex destroys the development of the original wake flow. The continuous development of the boundary layer is destroyed by multiple Terebridae-inspired ribs of T2, resulting in the broken wake. Through the comparison of vortex force, it can be seen that the vortex force of T1 is significantly weakened compared to that of T0, and this also indicates that the three-dimensional geometry of T1 can effectively reduce the intensity of the wake flow.

Spatio-temporal distribution of aerodynamic forces and their associated vortex drift patterns around a closed-box girder during torsional vortex-induced vibration

Torsional vortex-induced vibrations (VIVs) pose potential risks to prototype bridges with increasing spans and lower damping levels. However, the underlying mechanism remains unclear. Wind tunnel tests revealed that torsional VIVs occurred at an initial attack angle of + 3°. To unravel the VIV mechanism throughout the lock-in range, encompassing the ascent stage, amplitude extremum, and descent stage, the spatio-temporal distribution of aerodynamic forces around the bridge girder was analyzed. The results demonstrated the presence of traveling pressure waves with approximately 2.5 wavelengths and three uniformly distributed separated vortices over the upper side throughout the lock-in range. The primary source of these travelling pressure waves stemmed from the vortex drift patterns, with the aerodynamic wave travelling velocity equating the vortex drift velocity. The formation of separated vortices, known as the “double-vortex model”, occurred at the windward barrier on the upper side and windward maintenance rail on the lower side. These vortices directly imposed travelling pressure waves on the girder, thereby inducing torsional VIVs. Among them, the former vortices contributed more to the VIVs than the latter. Therefore, the formation of separated vortices and their related aerodynamic waves in the windward edge with the 2nd SVM/AWM modes predominantly governed the occurrence of torsional VIVs. Furthermore, both the ratio of the wave travelling time to the vibration period and the mean value of the wave travelling velocity ratio exhibited an inverse relationship with the VIV responses. However, the actions exerted by the vortex drift patterns were proportional to the VIV responses on both the upper and lower sides. Therefore, there existed evolutionary characteristics of aerodynamic waves and their related vortex drift patterns throughout the lock-in range, which was responsible for the “lock-in” phenomena.

Establishment and application of a digital twin for vortex-induced vibration of a bridge deck section

ABSTRACT Wind tunnel tests or computational fluid dynamics (CFD) simulations of the aeroelastic model of a bridge deck section are currently used to make sure that significant vortex-induced vibration (VIV) of a long-span bridge will not occur after the bridge is put into operation. However, significant VIV still occurred in several long-span bridges in operation, indicating that the currently used wind tunnel tests and CFD simulations have some drawbacks or uncertainties. This study aims at establishing a digital twin by interacting CFD simulation with wind tunnel test for accurately and efficiently predicting the VIV response of a bridge deck. The measurement information of VIV of the deck section is collected from the wind tunnel test and fused with the CFD simulation. The optimisation for reducing uncertainties existing in wind tunnel test and CFD simulation is then carried out to make the CFD simulation as a digital twin. The digital twin is finally used to investigate the blockage effect of wind tunnel test and give an accurate and efficient prediction of VIV of the bridge deck. The flat closed-box steel deck section used in the Xiangshan Harbor cable-stayed bridge is selected as a case study. The results from the case study show that the digital twin can be established and used for an accurate and efficient prediction of VIV of the bridge deck section.

Numerical investigations of the effects of spanwise grooves on the suppression of vortex-induced vibration of a flexible cylinder

Numerical investigations of Vortex-induced Vibration (VIV) suppression of a flexible cylinder with spanwise grooves in the uniform flow have been conducted by viv3D-FOAM-SJTU solver, which imports the thick strip model into OpenFOAM. The Reynolds-averaged Navier-Stokes (RANS) method is adopted to calculate hydrodynamic forces at each fluid strip. The vibrations of cylinder are solved through the Euler-Bernoulli bending beam hypothesis and the Finite Element Method (FEM) in two directions. During simulations, four spanwise grooves are arranged equally around the cylinder with an interval of 90° at two configurations. The spanwise groove keeps a constant width of w = 0.2D and a variable groove depth among 0.08D, 0.12D and 0.16D. Specific comparisons on Root Mean Square (RMS) vibration displacements, vibration modal responses, vibration frequency responses and vortex structures are conducted to analyze suppression effects of the spanwise grooves. Numerical studies indicate that the appropriate choose of groove geometry and arrangement can effectively reduce both crossflow and inline VIV responses.

Response Characteristics and Suppression of Vortex-Induced Vibration of the Flexible Cable

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 80[Formula: see text]mm and a length of 10.48[Formula: see text]m 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.