Vortex-induced Resonance Research Articles

Experimental and numerical studies on the two “lock-in” regions characteristic of vertical vortex-induced vibration of Π-shaped composite bridge deck

The Π-shaped bridge deck may easily occur vertical vortex-induced vibration, due to the bluff body aerodynamic configuration, which may cause the uncomforting of vehicles and pedestrians on the bridges. The present study mainly focused on the two “lock-in” regions characteristics of vertical vortex-induced vibration (VIV) of Π-shaped bridge deck, which can reveal the aerodynamic mechanism of vibration mitigation countermeasures. The vertical VIV response of original Π-shaped deck and those with different countermeasures are experimentally investigated detailly. Computational fluid dynamics (CFD) method is employed to numerically simulate the surrounding flow field of original girder section and those with different aerodynamic countermeasures. The numerical method is firstly verified through the comparison with the results of corresponding experimental results obtained in wind tunnel test. Afterwards, the flow pattern and vortex structure around the girder section simulated by CFD are utilized to interpret the effects of the mitigation countermeasures. The numerical results show that: (a)The vibration mitigation effect in the first vortex “lock-in” region is not sensitive to the position of the aerodynamic countermeasures, while the vibration mitigation effect in the second “lock-in” region is more sensitive to the position of the aerodynamic countermeasures; (b) The phase of aerodynamic lift and displacement response is close to synchronization in the ascending section of the VIV amplitude, greater than 90° in the descending section, and close to 180° outside the vortex-induced resonance range. The first vertical VIV region is related to the “Karman vortex street” at the trailing edge of the section, while the second vertical VIV region is related to the vortex shedding at the lower edge of the front end of the section and the secondary vortices on the upper surface.

Wind-induced vibration absorption using inerter-based double tuned mass dampers on slender structures

Controlling wind-induced responses is important for structural safety, especially for slender structures. Tuned mass damper (TMD) has been widely applied and shown the effectiveness in controlling vibration responses. Currently, inerter-based tuned mass systems have been proposed and shown excellent control performance, and the tuning mass can be reduced compared to TMD. However, the control performance depends on more parameters. The optimal design of these systems is a challenging task. In this paper, inerter-based double tuned mass dampers (IDTMDs) with three typical configurations are investigated. Firstly, frequency response functions are derived from mechanical impedance. Subsequently, the H∞ and H2 optimization results are obtained numerically and the corresponding empirical formulas are proposed. Next, the control performance of the wind-induced response is obtained by considering the spectral characteristics of along- and cross-wind loads. In order to quantitatively evaluate the weight reduction using IDTMDs, the control ratios are formulated and compared. Finally, the wind-induced vibration control of IDTMDs on a slender chimney and a tall building is investigated to validate the proposed empirical formulas. In addition, the control performance and weight reduction are discussed. Compared to TMD with similar control performance, IDTMD can reduce the tuning mass by 24%. The wind load of the chimney under vortex-induced resonance is reduced by 60%, and the peak value of total wind-induced acceleration is reduced by 30%, which is 26.2% better than TMD with a same mass ratio. A lightweight design with excellent wind-induced vibration control performance can be achieved by IDTMD.

Evaluation the possibility of vortex-induced resonance for a multistage pressure reducing valve.

A multistage pressure reducing valve is presented in this paper. The pressure reducing components are specially designed to not only control the flow rate but also effectively prevent the cavitation vibration. However, when the fluid flows through the pressure reducing components, the divergence and shedding of the vortices in the flow field seriously affect the stability of the valve and cause vortex-induced vibration. Especially, the main frequency of the vortex shedding is in the same frequency range as the modal frequency of the valve, the vortex-induced resonance of the valve occurs. It seriously affects the safety of a control system. In this paper, by monitoring the lift coefficient of the vortex cross flow in the valve, the frequency spectrum information of the lift coefficient is used as the novelty indexes to indicate vortex-induced vibration of the fluid in the valve. The main frequency and amplitude of vortex-induced vibration are obtained. The factors affecting the vortex-induced vibration of the fluid are analyzed. The results indicate that vortex-induced vibration is the most serious when the valve is opened or closed. The variation of the flow velocity and the pressure difference have obvious effects on vortex-induced vibration of the valve. The intensity of the variation affects the main frequency and amplitude of vortex-induced vibration. Using thermal-fluid-solid coupling modal analysis instead of traditional modal analysis, the modal frequency under the working state of the valve is obtained. It is compared with the main frequency of vortex shedding, and vortex-induced resonance does not occur in the multistage pressure reducing valve.

Preliminary Design Guidelines for Considering the Vibration and Noise of Low-Speed Axial Fans Due to Profile Vortex Shedding

This paper presents a critical overview on worst-case design scenarios for which low-speed axial flow fans may exhibit an increased risk of blade resonance due to profile vortex shedding. To set up a design example, a circular-arc-cambered plate of 8% relative curvature is investigated in twofold approaches of blade mechanics and aerodynamics. For these purposes, the frequency of the first bending mode of a plate of arbitrary circular camber is expressed by modeling the fan blade as a cantilever beam. Furthermore, an iterative blade design method is developed for checking the risky scenarios for which spanwise and spatially coherent shed vortices, stimulating pronounced vibration and noise, may occur. Coupling these two approaches, cases for vortex-induced blade resonance are set up. Opposing this basis, design guidelines are elaborated upon for avoiding such resonance. Based on the approach presented herein, guidelines are also developed for moderating the annoyance due to the vortex shedding noise.

부공력감쇠를 고려한 와류하중모델의 진동예측성능

The negative aerodynamic damping is a very crucial parameter in estimating the vortex induced resonance(VIR) in the across-wind direction. Aerodynamic damping is a major factor constituting so-called motion induced load or feedback load, and it is also a tool to explain the rapid manifestation of VIR. In this study, a mathematical model of aerodynamic damping are evaluated, and a process for predicting vortex induced vibration(VIV) along with vortex induced load model is proposed. By performing aeroelastic model test of a slender structure with a rectangular section, the aerodynamic damping and vortex-induced load are identified from the measured acceleration, based on these results, the mathematical models for aerodynamic damping and vortex induced load with respect to the wind speed were constructed. Finally, vibration estimation performance was evaluated by comparing the measured acceleration with the acceleration response obtained through re-analysis using the aerodynamic damping model and the vortex induced load model. From the numerical results, it was found that mathematical model of across wind load model are able to reliably predict VIV with a high reliability.

Case study of vortex-induced vibration and mitigation mechanism for a long-span suspension bridge

The wind-induced vibration of long-span bridges mainly manifests as flutter, galloping, vortex-induced vibrations (VIVs), buffeting, etc. Among these, VIVs cause vertical or torsional single-mode vibrations of the main girder; these affect the comfort of drivers or pedestrians on the bridge when vortex-induced resonance occurs. In this study, field measurements, numerical simulations, and wind tunnel tests were used to systematically investigate triggering mechanism during the sudden first and secondary VIV phenomena of Humen Bridge, along with the structural mode and damping characteristics and VIV aerodynamic mitigation effects, etc. The results show that the sudden first VIV was caused by the temporary installation of water-filled barriers, as these changed the aerodynamic configuration of the box girder; the decisive removal of these water-filled barriers can effectively suppress the VIV amplitude to some extent. The succedent secondary VIV was caused by the reduction of the structural damping; therefore, aerodynamic control and damping control measures are proposed. The aerodynamic control measures include the implementation of suppressor plates on the top of handrails and removal of the maintenance rails under the girder, whereas the structural damping control measures involve the successive installation of tuned-mass damper (TMD) to compensate for the reduced damping owing to the former large-amplitude VIV performance. After verification based on reduced-scale model wind tunnel tests, the aerodynamic control measures and structural damping control measures are successfully adopted and applied to Humen Bridge. These measures are shown to effectively suppress VIVs, as confirmed via succedent long-term on-the-spot observations.

2D and 2.5D Numerical Simulations for Vortex-Induced Vibration (VIV) of a 1.5:1 Rectangular Cylinder

The semi-periodic vortex-shedding phenomenon caused by flow separation at the windward corners of a rectangular cylinder would result in significant vortex-induced vibrations (VIVs). Based on the aeroelastic experiment of a rectangular cylinder with side ratio of 1.5:1, 2-dimensional (2D) and 2.5-dimensional (2.5D) numerical simulations of the VIV of a rectangular cylinder were comprehensively validated. The mechanism of VIV of the rectangular cylinder was in detail discussed in terms of vortex-induced forces, aeroelastic response, work analysis, aerodynamic damping ratio and flow visualization. The outcomes showed that the numerical results of aeroelastic displacement in the cross-wind direction and the vortex-shedding procedure around the rectangular cylinder were in general consistence with the experimental results by 2.5D numerical simulation. In both simulations, the phase difference between the lift and displacement response increased with the reduced wind speed and the vortex-induced resonance (VIR) disappeared at the phase difference of approximately 180∘. The work done by lift force shows a close relationship with vibration amplitudes at different reduced wind speeds. In 2.5D simulations, the lift force of the rectangular cylinder under different wind speeds would be affected by the presence of small-scale vortices in the turbulence flow field. Similarly, the phase difference between lift force and displacement response was not a constant with the same upstream wind speed. Aerodynamic damping identified from the VIV was mainly dependent on the reduced wind speed and negative damping ratios were revealed at the lock-in regime, which also greatly influenced the probability density function (PDF) of wind-induced displacement.

Vortex-induced vibration control of a streamline box girder using the wake perturbation of horizontal axis micro-wind turbines

The horizontal axis micro-wind turbine (HAMWT), a wind energy harvesting device, always engenders the streamwise component vorticity, which can potentially be applied to perform 3-D spanwise-varying control. As vortex shedding behind a bluff body is always efficiently suppressed via a 3-D spanwise-varying method, the HAMWT can be used to efficiently suppress the vortex-induced vibration (VIV). The control effect on mitigating the VIV of a streamline box girder is investigated through wind tunnel tests with HAMWTs installed in the spanwise direction. The results show that spanwise-distributed HAMWTs have significant control effects in suppressing the vortex-induced response with a symmetrical arrangement. As the spanwise distance and the height of the HAMWT decrease, the control effects improve. When the spanwise distance L < 3H and the height h < 0.3H (where H is the bridge deck height), the vortex-induced vibration is almost completely suppressed. Moreover, HAMWTs with a staggered arrangement are more effective than those with a symmetrical arrangement, and ultimately suppress the VIV response at different spanwise distances (at least at L = 1H–6H). Furthermore, wake analysis results indicate that wind turbines suppress vortex shedding, and the vortex-induced resonance is significantly weakened.

An improved firefly algorithm for identifying parameters of nonlinear empirical models

The nonlinear model is to describe the vortex-induced resonance of long-span bridges under the action of natural wind. The identification accuracy of its parameters directly affects people's understanding of vortex-induced vibration. People have been trying different algorithms to solve this parameter identification problem, but the efficiency and accuracy of algorithms are not satisfied. In this work, a firefly algorithm based on local chaos search and brightness variant (FACLBV) is proposed. The characteristics of chaos make FACLBV search the widely local scope and improve the accuracy of the solution. FACLBV modifies the fixed initial brightness, discards the absorption coefficient of light intensity, links the initial brightness of every firefly with the position of its solution space, and sets the attraction of every firefly as a simple linear function, which reduces the complexity of the algorithm and improves the efficiency. In order to better verify the superiority of FACLBV, the simulation experiment includes three parts: the comparison between FACLBV and other firefly algorithms, the verification of the parameters identified by FACLBV, and the nonparametric test between FACLBV and other intelligent algorithms. Simulation results show that FACLBV is better than other algorithms in performance.

Experimental study on wind-induced vibration and aerodynamic mitigation measures of a building over 800 meters

The new-generation high-rise buildings are taller and more flexible than before. Rigid model and aeroelastic model tests of a proposed steel super high-rise building with a height of 838 m were carried out in two simulated typical wind fields defined in the Chinese code [1] and the ISO standard (ISO 4354) in an atmospheric boundary layer wind tunnel. The wind pressure distributions of the building were obtained through the rigid model tests and then the wind-induced vibration responses of the building were calculated. Through the aeroelastic model test, the vibration responses of the building, which naturally include the wind–structure coupling effects, were directly obtained. The test results shows that strong crosswind vortex-induced resonance may appear at high wind speeds. Based on these results, the crosswind aerodynamic damping of the building was then studied. Finally, seven aerodynamic measures for controlling the wind-induced vibrations of the building were proposed and tested. The results show that the seven proposed aerodynamic measures can reduce the dynamic responses of buildings in different degrees.

Investigation of the Scruton Number Effects of Wind-Induced Unsteady Galloping Responses of Bridge Suspenders

When the critical wind speed of vortex-induced resonance is close to that of quasi-steady galloping, a type of coupled wind-induced vibration that is different from divergent galloping can easily occur in a rectangular bar. It is a type of “unsteady galloping” phenomenon wherein the response amplitude increases linearly with the increase in the wind speed, while a limit cycle oscillation is observed at each wind speed, whose mechanism is still in research. Mass and damping are the key parameters that affect the coupling degree and amplitude response estimation. For a set of rectangular section member models with a width-to-height ratio of 1.2, by adjusting the equivalent stiffness, equivalent mass, and damping ratio of the model system and performing comparative tests on the wind-induced vibration response of the same mass with different damping ratios, it is possible to achieve the same damping ratio with different masses and the same Scruton number with different masses and damping combinations under the same Reynolds number. The results show that the influence of the mass and damping parameters on the “unsteady galloping” amplitude response is independent, and the weight is the same in the coupling state. The Scruton number “locked interval” (12.4–30.6) can be found in the “unsteady galloping” amplitude response, and the linear slope of the dimensionless wind speed amplitude response curve does not change with the Scruton number in the “locked interval.” In addition, a “transition interval” (26.8–30.6) coexists with the “locked interval” wherein the coupling state of the wind-induced vibration is converted into the uncoupled state. The empirical formula for estimating the “unsteady galloping” response amplitude is modified and can be used to predict the amplitude within the design wind speed range of similar engineering members.

Analysis on flow induced vibration of main steam bypass valve in a nuclear power plant

Based on the fact that the main steam bypass system of a nuclear power plant vibrates violently during operation, the failure of couplings and other parts of the bypass valve occurs many times, which seriously affects the safe operation of the unit. According to bypass discharge system, and the bypass valve related drawings bypass valve fluid dynamics model is established, on the opening of the bypass valve interior flow field in CFD numerical simulation analysis, combining with the field vibration test results, for the opening of the bypass valve interior flow field in CFD numerical simulation analysis and vibration mechanism research, found that the structure of the piping system vibration and vortex shedding in the valve to inspire the chattering of the valve stem and even the axis of the main causes of fracture and valve is the high degrees of vortex-induced resonance is the main reason of the turbulent flow hood.

Auto-parametric sloshing in a rectangular aqueduct excited by wind vortex-induced vibration: experimental investigation and stability analysis

The vortex-induced vibration of the aqueduct girder may excite the parametric sloshing of the contained water which will have substantial impacts on the normal running and structural safety of the aqueduct bridge. This paper first conducts a wind-tunnel experiment to investigate the auto-parametric sloshing caused by wind vortex-induced vibration for an elastically-hung rectangular aqueduct with contained water. When the vortex excitation frequency is close to the natural frequency of the structure and approximately equal to twice the natural frequency of the fluid the vortex-induced resonance of the structure and the strong auto-parametric sloshing (internal resonance) of water successively occur in the test. The auto-parametric sloshing for the non-internal resonance case is also experimentally investigated. The contained water can be simplified as a rigid mass for the stability analysis of sloshing. The instability boundaries of sloshing and the corresponding wind speed regions are theoretically determined and compared with the experimental results

Comparison between an uncoupled one-way and two-way fluid structure interaction simulation on a super-tall slender structure

This paper presents a comprehensive analysis on a super-tall structure where a numerical approach is used to measure its structural response when subjected to turbulent wind. The aim of this study is to provide a feasible alternate approach, to the experimental multi-degree of freedom (MDOF) aeroelastic wind tunnel tests, which are commonly used in industry to estimate structural responses of super-tall structures. An innovative and time-efficient uncoupled one-way Fluid-Structure Interaction (FSI) simulation technique was used to measure the structural response. This novel method was evaluated against a commercially available two-way FSI analysis technique and validated with an experimental MDOF aeroelastic model. It is shown that the uncoupled one-way FSI analysis is capable of estimating structural responses and provides similar numerical accuracy to that of the experimental response. This performance was achieved in a total of 74clock hours which accounts for the CFD simulation and transient structural analysis calculated for eighteen different structural configurations. In comparison, the two-way FSI analysis, which uses a commercial code, took 4800clock hours to calculate for six configurations. The uncoupled one-way FSI technique also provided good correlations with experimentally observed trends such as vortex-induced resonance. In comparison the two-way FSI simulation was not as accurate due to the practical limitations (such as mesh size) that needed to be introduced in order to obtain results within a feasible time frame. Finally through validation, it is demonstrated that the proposed uncoupled one-way FSI analysis technique can provide accurate results at a feasible cost.

Reproduction of the wind and earthquake coupled effect on a wind turbine tower in a shaking-table substructure test

Wind turbines are being used in increasingly complex working environments that generate coupled wind and earthquake effects. Recent projects have tended to construct larger wind turbines to improve efficiency, but this generates more wind-induced vibration. Moreover, different threats are faced by a wind turbine at various stages. During construction, for example, vortex-induced resonance might result in a large lateral displacement of up to 1 metre, making the installation of blades difficult. Meanwhile, during service, the structure of a wind turbine can be damaged by strong gales and sometimes by earthquakes. The present study develops a tuned mass damper, which is designed to mitigate vortex-induced resonance. Shaking-table substructure hybrid tests are conducted to verify the performance of the tuned mass damper for different external loads. The experimental results confirm the effectiveness in terms of suppressing vortex-induced resonance, while the mitigation of the response to wind and earthquakes is limited.

Reproduction of the wind and earthquake coupled effect on a wind turbine tower in a shaking-table substructure test

Wind turbines are being used in increasingly complex working environments that generate coupled wind and earthquake effects. Recent projects have tended to construct larger wind turbines to improve efficiency, but this generates more wind-induced vibration. Moreover, different threats are faced by a wind turbine at various stages. During construction, for example, vortex-induced resonance might result in a large lateral displacement of up to 1 metre, making the installation of blades difficult. Meanwhile, during service, the structure of a wind turbine can be damaged by strong gales and sometimes by earthquakes. The present study develops a tuned mass damper, which is designed to mitigate vortex-induced resonance. Shaking-table substructure hybrid tests are conducted to verify the performance of the tuned mass damper for different external loads. The experimental results confirm the effectiveness in terms of suppressing vortex-induced resonance, while the mitigation of the response to wind and earthquakes is limited.

Fracture Mechanism Analysis and Structural Improvement for 1000-kV UHV Shield Ring

Some fracture failures of multiple shield rings on a 1000-kV ultra-high voltage transmission line have been found in succession. The method of reinforcing and welding at the fracture site were used to avoid crack enlargement. However, the reinforced shield rings were damaged again after half a year's use. A new approach is proposed to extract the root cause. The finite-element method is employed to calculate the static performance of shield ring for determining that the cause of the crack is not the ultimate strength failure of the material. And after acquiring the wind vibration frequency by vibration image recognition method, the critical vibration wind speed is obtained by the vortex-induced resonance analysis. And based on the critical speed, the lift force function is formed. According to the historical load simulated by lift force function, the displacement and stress response under the vortex-induced resonance are acquired by transient dynamic calculation. With the regional meteorological data of the transmission line, the probability of the wind direction and velocity within the critical vibration wind speed range is calculated out. Then, with the probability, the displacement and stress response and the vibration frequency of shield ring, the fatigue life assessment is conducted. Inspired by the idea of the energy dissipation-seismic reduction, a new type shield ring is designed. After testing the mechanical and electrical performance, the new one runs perfectly without emerging crack from November 2016, that verified the effectiveness of the design scheme for the new type shield ring.

Experimental investigation of vortex-induced vibration of a thousand-meter-scale mega-tall building

To ensure acceptable performance for survivability, serviceability and habitability of the mega-tall buildings, it is necessary to study their wind-induced response characteristics and vortex-induced resonance mechanism. In this study, the wind-induced responses of a thousand-meter-scale four-tower-connected mega-tall building are investigated using the aeroelastic model test in a boundary layer wind tunnel. The results show that the root mean square across-wind tip displacement increases dramatically within a certain wind velocity range at 60°wind direction, which indicates that the vortex-induced resonance occurs. Accordingly, the relation between the aerodynamic damping ratio and reduced wind velocity is further studied at this wind direction. Furthermore, the underlying mechanism of vortex-induced vibration (VIV) is comprehensively discussed based on the amplitude spectra of the across-wind tip displacements, which facilitates the identification of corresponding lock-in region. The identified critical reduced wind velocity for vortex-induced resonance for the mega-tall building is 10.19, with a lock-in region from 10.19 to 11.70. In addition, the VIV-like phenomenon occurred in the along-wind direction for this complex mega-tall building, associated with VIV in the across-wind direction. This observation indicates that there is aerodynamically coupled vortex shedding of the mega-tall building in the two directions. This study contributes to a detailed insight of the VIV phenomenon for the thousand-meter-scale four-tower-connected mega-tall building, and hence facilitates the wind-resistance design of this type of flexible structures.

Vortex-Induced Vibration Response Bifurcation Analysis of Top-Tensioned Riser Based on the Model of Variable Lift Coefficient

Top-tensioned riser (TTR) is one of the most frequently used pieces of equipment in offshore petroleum engineering. At present, the research of its vortex-induced vibration (VIV) is mainly focused on numerical simulation with few analytical approaches. In this paper, the nonlinear dynamic equation of VIV about TTR is developed by introducing the third-order variable lift coefficient hydrodynamic model. The amplitude-frequency response equation under 1:1 primary resonance excitation is deduced based on the single mode discrete results. The nonlinear dynamic responses characteristics of the TTR vibration under the excitation of vortex-induced resonance are discussed. Bifurcation theory is used to study the singularity of the analytical solution of the riser system. The hysteresis and solitary solutions from the results of singularity analysis are found. Such results can provide guidance for the design and optimization of riser structural parameters.

Parameter Identification Method Based on Model Degradation

Vortex-induced resonance is a complex coupling phenomenon. Vortex-induced vertical force (VIVF) model describes the characteristics of the vortex-induced force in resonance. Improper parameters can distort the model, so accurately identifying the parameters of the model is a current research hotspot. In this paper, a parameter identification method based on model degradation is proposed. A constant term is used to replace the harmonic force term in the model. The degenerated model is a linear combination of the nonlinear basis functions. Therefore, the linear fitting method is used to identify the model parameters. Based on the fit of VIVF, the performance of identification algorithm is evaluated. The results of Wilcoxon’s and Friedman’s nonparametric tests show that the identification algorithm is the best.