Vortex-induced Response Research Articles

Spectral modeling on the vortex-induced response of a tapered circular cylinder based on experimental evidence

This paper illustrates the application of spectral modeling for analyzing the vortex-induced vibration (VIV) response specifically focusing on a complex scenario involving a tapered circular cylinder exposed to uniform, stationary wind flow characterized by a low level of upstream turbulence. Such modeling is based on experimental evidence gathered during a wind tunnel campaign conducted through both static and dynamic tests. In particular, the definition of the limiting root mean square (RMS) amplitude, the variation of the RMS lift coefficient and of the Strouhal number along the height of the structure result to be crucial in the assessment of the dynamic response. A first model is proposed, based on the outcomes from static tests and from additional insight inferred from the dynamic response. Observing its comparison with the experimental findings in terms of oscillation amplitudes and peak factors, a second refined model is proposed. Moreover, the dynamic behavior of the structure is also investigated through the approach proposed by Engineering Science Data Unit (ESDU) 96030 for tapered structures. The results obtained from applying the spectral model reveal a satisfactory agreement with the experimental outcomes. This accuracy can be significantly attributed to the reproduction of the cellular nature of the vortex-shedding, achieved through an appropriate definition of the Strouhal number along the height of the cylinder. Furthermore, the modeled behavior reveals variations in the regime of the VIV response (e.g., deterministic, transition, stochastic) with respect to the reduced wind velocity, mirroring the findings of the experimental campaign.

Aerodynamic interference between road vehicles and bridge deck subjected to vortex-induced vibration

An accurate assessment of the driving comfort and safety of road vehicles moving on a long-span bridge subjected to vortex-induced vibration (VIV) is essential for bridge administrators to decide whether the bridge should be closed to traffic. However, previous assessments often ignore the aerodynamic interference between the road vehicles and the bridge deck subjected to VIV. In this study, a specific wind tunnel model is developed to explore the aerodynamic interference between road vehicles and twin-box bridge deck during VIV. The vortex-induced force (VIF) and vortex-induced response (VIR) of the twin-box bridge deck and the aerodynamic forces on the vehicle were simultaneously measured. The influence of the vehicles on the VIV of the deck was investigated, and the influence of the deck vibration on the aerodynamic forces of the vehicle was also explored. The results show that the VIR and VIF of the bridge deck were generally reduced, depending on the type, position, and number of vehicles. The aerodynamic forces of vehicles could be amplified due to the deck vibration. These findings supplement the database of vehicle aerodynamic coefficients for assessing the driving comfort and safety of road vehicles moving on a long-span bridge subjected to VIV.

Simulation and prediction of vortex-induced vibration of a long suspension bridge using SHM-based digital twin technology

Although wind tunnel tests have already become a design basis for improving the stability of long-span bridges under the action of wind loads, vortex-induced vibration (VIV) events of in-service long-span bridges have still been frequently reported in recent years. The reasons behind this could be attributed to the limitations and uncertainties involved in wind tunnel tests as well as the changes and degradations of in-service bridges. In consideration that most long-span bridges have now been equipped with long-term structural health monitoring (SHM) systems and that digital twins could provide a new solution for simulating and predicting the reality, this study aims at developing a digital twin for VIV of a long suspension bridge to simulate and predict its VIV. The design document-based finite element (FE) model of the bridge is first updated using the measured dynamic characteristics. The numerical model for VIV of the bridge is then established using the vortex-induced force (VIF) model established based on wind tunnel test results. The numerical model together with the VIF model are finally updated against the measured vortex-induced responses (VIR) to produce a digital twin for VIV of the bridge. The relationships between the parameters in the VIF model and wind characteristics are further investigated to enable the digital twin to predict future VIV events. The accuracy of the digital twin for predicting the future VIV and the influence of the VIF parameters obtained from wind tunnel tests on the prediction accuracy both are confirmed through comparisons between the predicted and measured results.

Vortex-Induced Force Identification of a Long-Span Bridge Based on Field Measurement Data

Vortex-induced force (VIF) identification and modelling of a long-span bridge are often conducted in terms of aeroelastic sectional model tests in wind tunnels. However, there are uncertainties inherent in wind tunnel model tests so that vortex-induced vibration (VIV) still occurs in real long-span bridges designed according to wind tunnel test results. This paper presents a framework for VIF identification of a long-span bridge based on field-measured wind and acceleration data. The framework is composed of the four steps: (1) decompose field-measured acceleration response time histories using variational mode decomposition (VMD) method; (2) obtain velocity and displacement response time histories using frequency domain integration (FDI) method; (3) establish and update the finite element model and identify the generalized VIF time histories of the bridge; and (4) identify the parameters in the polynomial VIF models and decide the most suitable VIF model. The proposed framework is finally applied to a real suspension bridge with a recent VIV event. The results show that the proposed framework can accurately identify the generalized VIF acting on the bridge from the field-measured acceleration and wind data, and the derived most suitable VIF model can produce almost the same vortex-induced response (VIR) as the measured ones.

Experimental investigations on the vortex-shedding from a highly tapered circular cylinder in smooth flow

This paper presents the results of a wind tunnel test campaign conducted to investigate the aeroelastic and aerodynamic behaviour of a tapered circular cylinder in smooth flow conditions. The model under investigation is a single-mode aeroelastic one, whose taper ratio (in terms of diameter) is 8 %. Its global dynamic response was measured through the use of an internally-mounted piezo-electric accelerometer. The sensitivity of the vortex-induced response to different levels of structural damping was explored. The harmonic content of the wake was also measured through a hot-wire anemometer positioned downstream of the wind tunnel model at different heights: this allowed the detection of the portion of the model whose local resonance was accountable for the highest vortex-induced structural response. To further expand the findings of the wake measurements, four ‘rings’ of surface-mounted pressure sensors were installed on the wind tunnel model. The Reynolds number that was covered during the experiments ranged between 9.3×103 and 3.2×104.The experimental investigations revealed that the tapering has a beneficial effect with respect to vortex-induced oscillations, reducing their magnitudes when compared against the ones of a parallel-sided circular cylinder. On the other hand, the lock-in region was found to be wider, exhibiting three distinct peak regions for the lowest level of structural damping. The combined results from the accelerometer, the hot-wire anemometer and the pressure measurements, and the application of tailored time–frequency analyses based on the continuous wavelet transform, revealed that the maximum dynamic response is linked to the local resonance between the fundamental frequency and the bottom portion of the structure. Furthermore, the magnitudes of the local mean aerodynamic drag coefficient and the local standard deviation of the (vortex-induced) lift coefficient were found to be considerably lower than those of a parallel-sided circular cylinder.

Turbulence Effects on Vortex-Induced Dynamic Response of a Twin-Box Bridge and Ride Comfort of the Vehicle

The rapid growth of suspension bridges’ span makes vortex-induced vibration (VIV) appears more and more frequently, and once it occurs the closure of the bridge results in considerable economic losses. Investigating the dynamic behavior of the bridge experiencing VIV and the vehicles running on it is thus imperative for providing a reliable guidance for the managers to make operation decisions. Nevertheless, most of the existing studies focus on VIV of bridges subjected to smooth winds, but a certain level of turbulence always exists in reality. The effects of turbulence on vortex-induced dynamic response of the bridge and ride comfort of the vehicles are not clear. This study thus develops a coupled vortex-vehicle-bridge system applicable to the multi-mode lock-in regions of a twin-box deck subjected to both vortex-induced forces and buffeting forces in a turbulent flow. The system is then applied to a real long suspension bridge with three types of vehicles subjected to either smooth or turbulent winds. The results from the case study show that the increasing turbulence mitigates vortex-induced responses of both the bridge and the vehicles and reasonably improves the vehicles’ ride comfort. However, the buffeting forces induced by turbulent wind component should not be ignored when turbulence intensity becomes high.

Wind-Induced Vibration and Vibration Suppression of High-Mast Light Poles with Spiral Helical Strakes

In this study, three-dimensional finite element models of high-mast light poles without and with spiral helical strakes were built using ANSYS software to investigate their vibration characteristics in a wind environment. Based on a two-way, fluid–structure interaction simulation method, the dynamic responses of the high-mast light poles under different windspeeds were analyzed. The results indicate that the high-mast light pole structure without spiral helical strakes may suffer from evident vortex-induced vibration, which is dominated by the third vibration mode in the windspeed range of 5~8 m/s, whereas the light pole with spiral helical strakes had no obvious vortex-induced vibration. The external helical strakes can amplify the along-wind response of the light pole to a certain extent, while significantly decreasing its crosswind vortex-induced response. The vibration suppression effect is better when the value of pitch P is small. Practically, if P = 7.5 D (D is the diameter of the dominant vibration mode), the vibration suppression effect is best. On the other hand, if the value of pitch P remains constant, the vibration suppression effect increases with the height H of the outer helical strakes. However, excessively high outer helical strakes may also increase the along-wind response of the structure. In general, when spiral helical strakes are used in design, the recommended values of P and H are P = 7.5 D and H = 0.20 D.

Tuned tandem mass dampers-inerters for suppressing vortex-induced vibration of super-tall buildings

Modern super-tall buildings with rectangular floor shapes are vulnerable to significant vibrations due to the vortex shedding effect formed around structural edges. Tuned tandem mass dampers-inerters (TTMDI) is extended in this study to suppress vortex-induced responses of super tall buildings for occupant comforts. The optimal TTMDI tuning problem for a 400 m super tall building exposed to crosswind loads is solved through frequency-domain analysis. Meanwhile, the control performance of TTMDI is explored and contrasted with that of the tuned mass damper (TMD), tuned tandem mass dampers (TTMD) and tuned mass damper‐inerter (TMDI) from various perspectives. A crosswind-resistant design framework of the TTMDI equipped super-tall building system is then devised to meet comfort requirements. Finally, results are further assessed in the time -domain using a virtual real time hybrid simulation (VRTHS) system based on the proposed hybrid model predictive controller. It is found that there are several optimal inertance coefficient redistribution points (i.e. R points) in the design process and the R points have a great impact on the optimal internal structure of TTMDI. Results clearly demonstrate that TTMDI has better effectiveness and robustness than TMD, TTMD, and TMDI. Moreover, the total demand for total damping coefficients of TTMDI is significantly smaller than TMDI after the R points, indicating that it is easier to implement in engineering practices.

Internal flow effect on the cross-flow vortex-induced vibration of marine risers with different support methods

The present work investigates the effect of internal flow on the vortex-induced vibration (VIV) characteristics of a marine riser under different boundary conditions. A numerical model of the riser structure is established by considering the complex flow fields. The developed model is solved by the finite element theory and Newmark method, and it is verified by the experimental data. The effects of internal flow velocity and density on the vortex-induced dynamic responses with different support methods are studied. The results demonstrate that among different support methods, internal flow effect (IFE) has the greatest influence on the vortex-induced response of the riser with hinged-cantilevered support. In the case of hinged-cantilevered support method, the increment of the internal flow velocity and internal flow density has a negative influence on the vortex-induced vibration of the riser. In the case of fixed at both ends support method, the vibration amplitude and mode of riser decrease with the increment of flow density in riser. For the hinged-hinged support condition, the increment of the internal flow velocity slightly increases the amplitude of the riser and the vibration amplitude of riser decreases with the increase of density. This research may provide an efficient method for the VIV prediction, optimization design and operation control of the marine risers in practical applications.

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.

Investigation of vortex-induced vibration of a cable-stayed bridge without backstays based on wind tunnel tests

Cable-stayed bridges without backstays located in the abrupt valley are sensitive to wind-induced structural vibrations. The understanding of vortex-induced vibration for specific aerodynamic configuration with glass deck is of great importance for structure design. This paper thus aims to investigate the vortex-induced vibration of a cable-stayed bridges without backstays through the segmental model test and scaled full-aeroelastic model wind tunnel test. The results indicate that the bridge presents the vertical vortex-induced vibrations at the low wind speed whereas the maximum wind velocity causing the torsional vortex-induced vibrations increases to 41 m/s, which is much larger than that of the traditional bridge. The vertical and torsional vortex-induced vibrations in the smooth flow are observed at the positive wind angle of attack, owing to the responses for the bridge deck present a sharp single-frequency amplitude when the frequency of vortex-shedding is close to the flexural vibration frequency. The turbulence can effectively suppress the vortex-induced vibrations and only some small peaks are visible in the turbulent flow. The vortex-induced response of the bridge deck is significantly alleviated with increasing of damping ratio. Finally, the vortex-induced vibrations in the uniform flow disappear and the wind-induced responses are impaired with the ventilated railing in place of the airtight railing because the flow can go through the railing. It can provide a designing basis for engineering reference of cable-stayed bridges without backstays.

An experimental study on vortex-induced motion responses of a moored semi-submersible with and without riser

This article presents an experimental study on the “vortex-induced motion” responses of a moored “semi-submersible without catenary riser” and “semi-submersible with catenary riser.” An eight-point catenary mooring system is adopted for the study in which eight rollers are installed on the pontoons for guiding the mooring lines and the semi-submersible design is of two rectangular pontoon and two circular columns on each of the pontoons. To replicate the real-world scene, the experiments are conducted in wave-cum-current flume with five directions of current (i.e. 0°, 30°, 45°, 60°, and 90°) to study the vortex-induced motion under the surge and sway degrees of freedom at high dimensionless reduced velocities (i.e. 6&lt; Urs&lt;50.86). Along with the surge and sway degrees of motion, the roll and pitch degrees of motion are investigated too with their paths for semi-submersible (i.e. amplitude traces). A “stainless steel flexible braided hose” with an aspect ratio of 157 till the touchdown point is used as a catenary riser. Results are presented with the definitions of degrees of freedom with respect to the axes defined at the center of gravity of semi-submersible and show that above the reduced velocity of 25 for the sway and surge degrees of freedom, the vortex-induced motion responses show a complex variation without any monotonicity. Furthermore, it is observed that (1) in traces there are no eight-shaped trajectories; (2) for both the semi-submersible without catenary riser and semi-submersible with catenary riser, the higher responses occur along the diagonals; (3) there are couplings of the pitch with surge, and roll with sway dofs; (4) the catenary riser reduces the vortex-induced motion responses for most of the current directions; and (5) galloping instabilities may be occurring and higher amplitudes may be related to them. Finally, it is shown that the vortex-induced motion response of semi-submersible reduces the vortex-induced vibration response of riser and that the motions in pitch and roll are likely to become critical and they demand a detailed analysis to be addressed in future to improve the operational range of semi-submersible and catenary riser in deep water depths under harsh marine environment of high current velocities.

Vortex-induced vibration of a truss girder with high vertical stabilizers

To improve the flutter stability of a long-span suspension bridge with steel truss stiffening girder, two vertical stabilizers of which the total height reaches to approximately 2.9 m were planned to install on the deck. As the optimized girder presents the characteristics of a bluff body more, its vortex-induced vibration needs to be studied in detail. In this article, computational fluid dynamics simulations and wind tunnel tests are carried out. The vortex-shedding performance of the optimized girder is analyzed and the corresponding aerodynamic mechanism is discussed. Then, the static aerodynamic coefficients and the dynamic vortex-induced response of the bridge are tested by sectional models. The results show that the vertical stabilizers could make the incoming flow separate and induce strong vortex-shedding behind them, but this effect is weakened by the chord member on the windward side of the lower stabilizer. As the vortex-shedding performance of the optimized girder is mainly affected by truss members whose position relationships change along the bridge span, the vortex shed from the girder can hardly have a uniform frequency so the possibility of vortex-induced vibration of the bridge is low. The data obtained by wind tunnel tests verify the results by computational fluid dynamics simulations.

Finite Element Analysis of Vortex Induced Responses of Multistory Rectangular Building

High-rise buildings may experience high levels of vibrations under the actions of wind which cause building motions, adversely affecting serviceability and occupant comfort. The paper analyzed the vortex shedding responses of a multistory building with moment resisting frame. It presents a numerical model based on computational wind engineering technique to simulate the wind action over a typical high-rise building using wind speed data of Lagos state Nigeria. The vortex shedding frequency of the vortices and the natural frequency of vibration of the entire high-rise building structural system were calculated by computing fast Fourier transform algorithm (FFT) of the force coefficient and finite element analysis (FEA) of the structural system respectively. From the result obtained, the vortex shedding frequency of the wind vortices was lower than the fundamental frequency of vibration of the typical high-rise building. Hence, vortex shedding was not responsible for the failure of high-rise buildings in the locality being considered due to the reasons stated in the author’s conclusion.

Finite Element Analysis of Vortex Induced Responses of Multistory Rectangular Building

High-rise buildings may experience high levels of vibrations under the actions of wind which cause building motions, adversely affecting serviceability and occupant comfort. The paper analyzed the vortex shedding responses of a multistory building with moment resisting frame. It presents a numerical model based on computational wind engineering technique to simulate the wind action over a typical high-rise building using wind speed data of Lagos state Nigeria. The vortex shedding frequency of the vortices and the natural frequency of vibration of the entire high-rise building structural system were calculated by computing fast Fourier transform algorithm (FFT) of the force coefficient and finite element analysis (FEA) of the structural system respectively. From the result obtained, the vortex shedding frequency of the wind vortices was lower than the fundamental frequency of vibration of the typical high-rise building. Hence, vortex shedding was not responsible for the failure of high-rise buildings in the locality being considered due to the reasons stated in the author’s conclusion.

Vortex induced vibration of an inclined finite-length square cylinder

This study investigated vortex-induced vibrations of a slender square-section cylinder inclined from the vertical direction by a series of angles experimentally. Both aeroelastic tests and pressure measurements were performed on the cylinder with forward inclinations (inclined to the upwind direction), a vertical attitude, and backward inclinations (inclined to the downwind direction) in a wind tunnel. The cylinder was kept stationary in the pressure measurement tests. The aeroelastic test results show that vortex-induced responses of the cylinder decrease considerably as increasing the forward inclination angle. By contrast, the effect of the backward inclination on the vortex-induced vibration varies. Not all the backward inclined cylinders exhibit crosswind responses smaller than those of the vertical cylinder does. The responses of the cylinder with a small backward inclination are significantly larger, whereas the cylinder with a large backward inclination exhibits lower responses than those of the vertical case. The variation in the vortex-induced vibration response with the inclination is explained by performing power spectral analyses on the pressure data on the side face over the cylinder span, which reveals local vortex shedding characteristics. The findings provide significant guidance to the wind-resistant design of an inclined slender structure.

Vortex-Induced Motion Response of Semi-Submersible Platform in Deep Water: II. Investigation on Hull Optimization

Vortex-Induced Motion Response of Semi-Submersible Platform in Deep Water: II. Investigation on Hull Optimization

Vortex-Induced Motion Response of Semi-Submersible Platform in Deep Water: I. Investigation on Key Characteristics

Vortex-Induced Motion Response of Semi-Submersible Platform in Deep Water: I. Investigation on Key Characteristics

Vortex-induced vibration analysis of long-span bridges with twin-box decks under non-uniformly distributed turbulent winds

With the increase of span length, long-span bridges become more flexible and susceptible to vortex-induced vibrations (VIV). Large-amplitude VIV may cause fatigue damage to structural components, and therefore accurate predictions of vortex-induced responses (VIR) are important. This paper proposes a mode-by-mode VIV analysis method for long-span bridges with twin-box decks under non-uniformly distributed turbulent winds. A semi-empirical model of vortex-induced forces (VIF), developed by the authors and validated by direct force measurements on an elastically-mounted twin-box section model under turbulent winds, is embedded in the VIV analysis method. The proposed analysis method is then used to analyze the VIV of a real long-span suspension bridge of a twin-box deck. The computed VIR of the prototype-bridge is finally compared with the VIR measured on-site by a structural heath monitoring system installed in the bridge. The comparative results show that the proposed VIV analysis method can be used to predict the VIR of long-span bridges with twin-box decks. Further studies also show that the non-uniform distribution of mean wind speed reduces the VIV of the bridge. Turbulence also diminishes the VIV of the bridge, and the reduction effect is larger on lower-order modes of vibration than on higher-order modes of vibration.

Effects of structural damping on wind-induced responses of a 243-meter-high solar tower based on a novel elastic test model

The effects of structural damping to the responses of the vortex-induced vibration of solar tower should be investigated carefully to provide a reference for the structural designers. A new type of elastic test model for a 243-meter-high solar tower is particularly designed and manufactured. A core beam is designed in the test model to simulate the stiffness of the concrete structure, and a coat with baseplate (like a cup) is designed to simulate the steel structure. A structural damping ratio as low as 0.3% is realized, and four level of structural damping ratio, including 0.7%, 1.0%, 1.5% and 2.0%, can be conveniently achieved. A series wind tunnel tests are carried out to investigate the features of the wind-induced responses of the solar tower at the structural damping level of 0.3%, 0.7%, 1.0%, 1.5% and 2.0%. The results show that obvious vortex-induced vibration could be found within wind velocity range of U10 = 21.5–28.4 m/s for the structural damping ratio of 0.7%. At this time, the highest vortex-induced responses (at the wind velocity of U10 = 23.2 m/s), including acceleration at the top, base shear and base moment, are far larger than those at the design wind velocity (U10 = 41.0 m/s). Moreover, it appears that the wind-induced responses in cross-wind direction are far higher than those in the along-wind direction. The most important point is that the base shear and moment in the cross-wind direction measured from wind tunnel tests are far higher than the values obtained from the Code ACI 307–08. The wind-induced responses of the solar tower are extremely sensitive to the structural damping of the test model. For example, the highest acceleration, base shear and moment in cross-wind direction are respectively reduced by about 67%, 74%, 71% when structural damping ratio slightly increases from 0.7% to 1.0%. It seems that the vortex-induced vibration of the solar tower could be effectively mitigated if the structural damping ratio could be enhanced over 1.0%.