Vortex-induced Resonance Research Articles

Analysis and control of hydrofoil vortex-induced vibration

This paper primarily investigates the relationship between the wake vortices and vortex-induced vibrations in hydrofoil structures, as well as explores effective methods to suppress structural vibrations in hydrofoils using a piezoelectric control system. By combining CFD simulations with PIV experiments, the study compared the vortex characteristics at the trailing edge of hydrofoils with different geometries. Furthermore, by integrating the results from the water tank experiments, the research revealed the sensitivity of vortex-induced resonance to the regularity and periodicity of the von Kármán vortex street. Subsequently, the FxLMS algorithm was fine-tuned based on a phenomenological model of vortex-induced resonance. Active control experiments on vortex-induced vibrations of the hydrofoil were conducted using a piezoelectric control system built on this algorithm, achieving a maximum vibration reduction rate of 56%. Finally, the instability and limitations of the control effectiveness were analyzed, and future research directions were proposed to improve control strategies and the system's temporal responsiveness.

Flow field characteristics and vibration responses of saddle-shaped membrane structures

Elastically mounted flexible membrane roofs exposed to flows are prone to vortex-induced vibrations and even aero-instability due to the strong fluid–structure interaction (FSI). This study is to investigate the FSI mechanism in the saddle-shaped membrane structure over a range of Reynolds numbers and wind directions in laminar flows, by bridging structural vibration responses and flow dynamics. The aeroelastic characteristics of membrane structures, including statistics of displacement responses, oscillation frequency, and oscillation damping ratios, were identified from the perspective of time and frequency domains. Simultaneously, the particle image velocimetry system was employed to visualize the flow features, including velocity vector, turbulence intensity, and vortex evolution in both space and time. The flow modes were further decomposed by proper orthogonal decomposition (POD) to capture the salient aspects of the flow. Three patterns of POD modes are identified, and the first mode plays the dominant role in POD modes. It showed that as the wind Reynolds number increases, the space between the shear layer and membrane surface would be narrowed, and resultantly the vortices turn out smaller in scale and closer in space. This trend leads to an increase in the frequency of vortex shedding and a stronger FSI effect. When the frequency of vortex shedding approaches the fundamental frequency of structures, the vibration of the membrane would be shifted from turbulent buffeting to vortex-induced resonance, featured with lock-in frequency, significant amplified displacement, and negative aerodynamic damping ratio.

Wind-induced vibration response of supertall sightseeing tower evaluation during construction through wind tunnel test of aeroelastic models

Four construction phases of an ultra-high sightseeing tower with a cable-barrel composite structure and their wind-induced vibration response were studied. The first-order natural vibration characteristic of the structure in four different construction phases was calculated through finite element models, and associated aeroelastic models were also designed. Meanwhile, rough strips are applied uniformly on the surface of the model to compensate the Reynolds number of the wind tunnel test. The performance of this method was investigated utilizing the pressure test of rigid segment models. The wind-induced vibration response under four construction conditions, and the effects of wind direction angle, wind speed and structural damping ratio were investigated through the wind tunnel test of aeroelastic models. The results show that sticking rough strips on the surface can effectively improve the Reynolds number of wind tunnel tests. As the wind speed during construction increases, the structural wind-induced vibration response intensifies. A large vortex-induced resonance occurs in the construction phase of a cable-barrel composite structure with the Strouhal number around 0.12 under turbulent conditions in this study. Furthermore, the crosswind-induced vibration response of the structure at a wind deflection angle of 0° is greater than 45° and 90°. Specifically, the mean value of downwind displacement and the maximum value of standard deviation (STD) of downwind and crosswind displacements on the prototype tower top at 0° during construction phases are 1.21 m, 0.35 m, and 0.25 m respectively. Thus, the risk of large wind-induced vibration should be fully considered during construction. Implementing corresponding damping measures to improve the damping ratio of the structure proves effective in restraining its vibration.

Experimental investigation of wind-induced vibration of multi-cross-section steel tube lightning rods in substation

The multi-cross-section steel tube lightning rod (MSTLR) in the substation are susceptible to along-wind buffeting and vortex-induced vibration due to their inherent flexibility, low damping properties and multi-circular-section. This paper conducted a wind tunnel experiment on a 1:5 aeroelastic model of MSTLR under three wind fields with different turbulence intensity (uniform, 4.0%, and 7.0%). The amplitude, PSD, time-frequency curves, frequency components, and trajectory of wind-induced vibration are analyzed by measuring the acceleration responses at different heights and bottom reaction responses in the along-wind and cross-wind directions. A comparison was made between the relevant wind load parameters and those specified in the Eurocode. The results indicate that the distribution of the key participating modes exhibits different patterns with the variance of wind speed and turbulence intensity. Multi-order vibrations and structural coupling in orthogonal directions are observed with total response higher than the Eurocode. With the increase of turbulence intensity from 4.0% to 7.0%, the contribution of turbulence to along-wind acceleration response reaches saturation and has the opposite effects. When the speeds are 21.55 m/s and 27.33 m/s, respectively, the vortex-shedding frequencies of section 2 and section 3 coincide with the second-order natural frequency, and the vortex-induced resonance occurs. Those two vortex-induced resonances lead to a sudden increase in the standard deviation of the cross-wind response.

Effects of turbulence integral length scales on aerodynamic characteristics and displacement responses of a square prism

This paper investigates the influence of the inflow turbulence integral length scales on the aerodynamic forces on a surface-mounted finite-length square prism and its displacement responses by computational fluid dynamics simulations. Four turbulent inflow conditions with the same mean wind speed and turbulence intensity but different longitudinal and transverse turbulence integral length scales are generated for the simulations. First, the wind pressures and forces on a rigid square prism model and the shear layer characteristics are simulated by large eddy simulations. The simulation results show that the mean characteristics of the wind pressures and shear layers are not sensitive to the turbulence integral length scales. However, the root mean square (RMS) wind pressures on side faces and RMS across-wind forces are increased with the longitudinal turbulence integral length scale, and the mechanism is analyzed by the proper orthogonal decomposition. Second, the displacement responses at the mean wind speed of vortex-induced resonance are computed based on an aeroelastic square prism model by fluid–solid interaction simulations. The RMS displacements of the model are observed to be more sensitive to the transverse turbulence integral length scale rather than the longitudinal turbulence integral length scale. Finally, the influence of the turbulence integral length scales on the Reynolds stresses around the square prism is presented and discussed.

Optimizing Coupled Fluid-Structure Simulations for Nuclear-Relevant Geometries

Abstract The numerical simulation of fluid-structure interactions (FSI) has gained interest to study flow-induced vibrations. Nevertheless, the high computational resources required by such simulations can represent a significant limitation for their application to industrial configurations. Therefore, simplified modeling approaches, when physically applicable, can represent an interesting compromise. This can be the case of slender structures (tubes, rods) often encountered in nuclear power plants. In this paper, an Euler–Bernoulli beam finite element model is implemented inside the computational fluid dynamics (CFD) code code_Saturne. With the goal of finding CFD methods less expensive than large eddy simulations (LES), unsteady Reynolds Navier–Stokes (URANS) and hybrid URANS/LES approaches are considered. The resulting fluid-structure model is able to calculate the vibration response of cantilever beams under a fluid flow, avoiding the necessity of CFD-finite element method (FEM) code coupling. The first part of the paper describes the model and its implementation: it allows to perform 2-way explicit fluid-structure coupling, using the Arbitrary Lagrangian-Eulerian approach to account for the structure deformations. Validation test cases are presented in the second part: first, the model is validated in terms of frequency, added mass, and damping for a cylinder vibrating in static air and water; then, the model is validated toward the vortex-induced resonance and lock-in mechanisms for a cylinder subjected to water cross-flow. The model is then applied to a real experimental configuration of two in-line cylinders in water cross-flow: the calculated vibrations are found to be in good agreement with the experimental measurements.

An assessment of CFD-scale fluid–structure interaction simulations through comprehensive experimental data in cross-flow

Experimental tests accessing both fluid and structure behaviors are mandatory for a consistent and comprehensive assessment of fluid–structure interaction (FSI) numerical simulations. In this paper, recently published results of an experimental configuration of two in-line cantilever cylinders subjected to water cross-flow were considered: instantaneous fluid velocities measurements are available on several positions inside the test section, together with the cylinder vibrations. FSI simulations were performed by coupling Ansys Fluent (for the fluid domain) with Ansys Mechanical (for the solid domain). URANS simulations and Scale-Adaptive Simulations (SAS) were employed as CFD simulation approach. The structure displacements were taken into account through an Arbitrary Lagrangian–Eulerian approach. The fluid–structure coupling was 2-way explicit. Simulations were performed for two different water mass flow rates. For the highest one, vortex-induced resonance was observed experimentally. The numerical results show consistent agreement in terms of shedding frequency and velocity spectra behind the cylinders. The calculated vibration response is overall consistent, despite some underestimations, for the cylinders not featuring vortex-induced resonance; nevertheless, the experimentally observed vortex-induced resonance could not be reproduced by the numerical simulations.

Fluid-solid interaction simulations of an aeroelastic square prism in sinusoidal oscillatory flows

This study numerically investigates the aerodynamic and aeroelastic characteristics of a square prism (aeroelastic model) and wind field around it in sinusoidal oscillatory flows (SOFs). The reliability of the fluid-solid interaction (FSI) simulation is validated by a free vibration test and wind tunnel tests in smooth flow and SOF. The effects of the amplitude and frequency of SOFs are studied at the mean wind speed of vortex-induced resonance. The results show that increasing the amplitude and frequency of SOFs will amplify the root mean square (RMS) along-wind and across-wind base shear forces of the aeroelastic model but decrease the RMS across-wind displacement at the top of the aeroelastic model. The spectral analysis of the base shear forces indicates that the influence of vortex shedding on the across-wind base shear force is reduced by either increasing the amplitude or increasing the frequency of SOFs. The mean and instantaneous wind fields around the aeroelastic model in SOFs and smooth flow are compared, and the wake characteristics of the aeroelastic model in SOFs are analysed by dynamic mode decomposition. It is observed that when the frequency of SOFs is 1.5 times as large as the fundamental natural frequency of the aeroelastic model, the regular vortex shedding process is substantially affected.

Nonlinear dynamic analysis of vortex-induced resonance of a flexible cable

Nonlinear dynamic analysis of vortex-induced resonance of a flexible cable

The interaction between cross-flow induced vibration and convection heat transfer in tube bundle at subcritical Reynolds number

This work numerically investigates the interaction between flow-induced vibration (FIV) and forced convection heat transfer in tube bundle with a pitch ratio of 1.5 at subcritical Reynolds number (Re = 5 × 103-3 × 104). The range of reduced velocity is 0.53 ≤ Vr ≤ 2.71. The mass-damping parameter of coupling system is 0.07. The three-dimensional refined FIV simulation considering fluid viscous damping has been validated by the literature experiment to capture three continuous FIV mechanisms, namely turbulence-induced vibration, vortex-induced resonance and fluidelastic instability. The heat transfer and pressure drop in tube bundle are validated by the experiment. The coupling of Navier-Stokes equations, energy equations and vibration equations is solved by under-relaxation algorithm. The results of vibration response, the change of damping for the coupling system, flow field and temperature field, heat transfer and pressure drop are presented and delineated in this paper. The results show that for the low velocity turbulence-induced vibration, the interaction between FIV and flow heat transfer is negligible due to the weak fluid–solid interaction. In vortex-induced resonance region, the wall heating makes each row tube be out of phase by affecting the vortex shedding and reduces the positive feedback of resonance, which reduces the amplitude. The wall heating reduces the damping of coupling system, which causes an earlier transition from vortex-induced resonance to fluidelastic instability and a faster increase of amplitude in fluidelastic instability. In both vortex-induced resonance and fluidelastic instability, the vibration of tube bundle dominates the vortex shedding by the natural frequency, and further dominates the change of heat transfer. The best performance of enhanced heat transfer induced by FIV is located in vortex-induced resonance region, in which the time–space averaged Nusselt number is increased by 8.83%. Due to the redistribution of flow field and the elimination of deflective flow pattern, compared with vortex-induced resonance, the increasing ratio of heat transfer induced by FIV is lower and the increasing ratio of pressure drop induced by FIV is higher in the fluidelastic instability.

The Influence of Aeroelastic Effects on Wind Load and Wind-Induced Response of a Super-Tall Building: An Experimental Study

To investigate the wind-induced response and equivalent wind load of a super-tall building, an aeroelastic model of the building was designed to measure aerodynamic interference in wind tunnel tests. Experiments on pressure and vibration measurements were conducted in both uniform and turbulent wind fields, and the displacement response and surface wind pressure at different locations of the model were recorded. The displacement time-history response spectrum and aerodynamic spectrum in both fields were compared and analyzed. The research showed that the mean displacement responses of the model in the across-wind and along-wind directions gradually increased with velocity under different wind attack angles. The mean displacement response of torsion moment in a uniform wind field changed very little, and the mean and fluctuating wind pressures in each layer were significantly stratified, making it is easy to generate a coupled vortex-induced resonance. On the other hand, the mean displacement response of torsion moment in a turbulent field increased with wind velocity. Strong turbulence made the fluctuating wind pressure at the top and bottom of the model slightly more significant than in a uniform field. The resistance of super-tall buildings came from turbulence excitation in the along-wind direction and the self-excited resistance generated by the across-wind direction. The test methods and main research conclusions may provide a reference for glass curtain walls and the structural wind-resistant design of super-tall buildings.

Study on the Vibration Characteristics of Marine Riser Based on Flume Experiment and Numerical Simulation

This study investigated vortex-induced vibrations of marine risers in Ocean Thermal Energy Conversion systems. Flume experiments were conducted under two conditions: Condition 1 was with a fixed riser bottom, and Condition 2 was with a fixed bottom on a mooring platform. The cross-flow acceleration of the riser was measured at different current velocities, and corresponding vibration responses were analyzed. Numerical simulations based on the flume experiments were employed to validate the reliability of the simulation method. Results from the flume experiments revealed vortex-induced resonance in Condition 1 when the flow velocity approached the riser’s natural frequency. In Condition 2, similar vibration responses were observed, with maximum acceleration occurring during flow velocity-induced vortex-induced vibrations. However, at higher flow velocities, the acceleration response showed a decrease followed by an increase, indicating the excitation of higher-order modes. The numerical simulations matched the flume experiments in Condition 1. In Condition 2, while the acceleration response and frequency agreed during vortex-induced resonance, discrepancies arose in the flow velocity that caused vortex-induced vibrations compared to the flume experiments. This study demonstrated the accuracy of numerical simulations in reflecting vortex-induced vibrations of risers, providing a foundation for further research on complex riser systems.

Solid-Liquid Triboelectric Nanogenerator Based on Vortex-Induced Resonance.

Energy converters based on vortex-induced vibrations (VIV) have shown great potential for harvesting energy from low-velocity flows, which constitute a significant portion of ocean energy. However, solid-solid triboelectric nanogenerators (TENG) are not wear-resistant in corrosive environments. Therefore, to effectively harvest ocean energy over the long term, a novel solid-liquid triboelectric nanogenerator based on vortex-induced resonance (VIV-SL-TENG) is presented. The energy is harvested through the resonance between VIV of a cylinder and the relative motions of solid-liquid friction pairs inside the cylinder. The factors that affect the output performance of the system, including the liquid mass ratio and the deflection angle of the friction plates, are studied and optimized by establishing mathematical models and conducting computational fluid dynamics simulations. Furthermore, an experimental platform for the VIV-SL-TENG system is constructed to test and validate the performance of the harvester under different conditions. The experiments demonstrate that the energy harvester can successfully convert VIV energy into electrical energy and reach maximum output voltage in the resonance state. As a new type of energy harvester, the presented design shows a promising potential in the field of 'blue energy' harvesting.

A three-dimensional refined numerical simulation of cross-flow induced vibration mechanism in the tube bundle

Cross-flow induced vibration causes many accidents in the nuclear steam generator tube bundle. An accurate and refined cross-flow induced vibration numerical simulation can help avoid accidents in the designed bundle for different geometries, and provide insights into flow-induced vibration mechanism. In this paper, a three-dimensional refined numerical simulation model considering the fluid viscous damping was established and validated. First, we validated the simulation of the viscous damping that structure suffered in the fluid, and studied the relationship between the fluid viscous damping and the structural spring damping in tube bundle coupling with fluid. The results showed that fluid viscous damping coefficient and the structural spring damping coefficient can be directly added to equal the total damping coefficient in the coupling system between the tube bundle and fluid. Then, a three-dimensional simulation based on SST-SAS (the Transition SST combined with the Scale Adaptive Simulations (SAS) turbulence model) was used to study flow-induced vibration for the literature experiment tube bundle. Simulation of flow-induced vibration had the same mass-damping parameters with the literature experiment. The vibration amplitude trend and spectra of the simulation were basically consistent with that of the experiment. Simulation accurately captured the onset of the vortex-induced resonance and the transition from the vortex-induced resonance to the fluidelastic instability. And the different mechanisms and their transition were analyzed. Specially, the flow field and structure analysis showed that the local vortex-induced resonance of the front-row tubes caused the synchronous resonance of the whole tube bundle.

Study on Wind-Induced Human Comfort of the SEG Plaza under Local Excitation Based on Wind Tunnel Test

Multiple unusual vibrations occurred in SEG Plaza from May 18 to 20, 2021. To investigate the causes of these vibrations, a rigidity compression wind tunnel test was applied to study the wind-induced response of the main structure, and acceleration sensitivity analysis was conducted with parameters such as wind speed, structural period and damping ratio included. Additionally, the mast vortex-induced resonance equivalent force of reaction in the bottom was exerted on the top of the structure to obtain the acceleration response of the main structure with mast. Based on the evaluation of the vibration response of the structure before and after considering the mast as per the current specifications, it is indicated that the base overturning moment of the structure is much smaller than the specification value excluding the factor of mast, and the acceleration response varies significantly with wind pressure, structural frequency and damping ratio, but the centroid acceleration and the angular acceleration meet the comfort requirements. This indicates that the wind load on the main structure is not the dominant cause of the structural vibration. With the mast taken into account, the acceleration response of the structure exceeds the limits of the comfort level to varying degrees. For a mast damping ratio of 0.3%, the maximum angular acceleration exceeds the H-90 limit and the comfort level is poor. These findings provide considerable evidence that the dominant cause of vibration in the SEG Plaza was the vortex resonance of the top mast inducing higher mode resonance in the main structure.

A Triboelectric Transduction Mechanism from Flow-Induced Low-frequency Structural Resonance

A triboelectric nanogenerator (TENG) based on the vortex-induced vibrational resonance is proposed to collect the kinetic flow energy of rivers and oceans. A prototype was fabricated to study the performance of the harvester. Experiments were conducted at flow velocities below 1 m/s. The results show that when flow velocity reaches a low level, the mechanism starts to vibrate; thus, the voltage can be generated, and the voltage increases with the growth of flow velocity. When flow velocity reaches a medium level, the structural resonance take place, resulting in the maximum amplitude of the device and voltage outputs which does not increase further with the growth of flow velocity. When flow velocity reaches a high level, the vortex-induced resonance phenomenon disappears so that amplitude and voltage decrease. The experimental results demonstrate the feasibility of using TENG to harvest vortex-induced vibration energy.

Vortex-induced vibration analysis of submerged floating tunnel tension legs

Considering the influence of axial and transverse vibration of tension legs of submerged floating tunnel, the non-linear vibration equation of the tension leg under the action of vortex-induced excitation is derived and solved numerically by Galerkin and Runge–Kutta methods. The results show that the vibration amplitude and frequency of tension legs under the action of vortex-induced excitation are related to the natural frequency of tension legs. Due to water damping, the vortex-induced vibration response of tension legs in submerged floating tunnel is lower than that of the tension leg in air; the shorter the length of the tension leg, the higher will be the current velocity needed to produce vortex-induced resonance; the larger the initial tension of the tension leg, the faster will be the current velocity needed to generate vortex-induced resonance; the transverse pulse force increases with an increase of the initial tension and the outside diameter of the tension leg, and decreases with an increase of the length of the tension leg.

Investigation on modal coupling–aeroelastic effect of a super tall building by MDOF aeroelastic model test

The prototype buildings in existing wind tunnel tests on the aeroelastic effect of super tall building are mostly hypothetical and not consider the modal coupling. In this paper, a multi-degree-of-freedom aeroelastic model was designed and wind tunnel tests were performed to research the modal coupling–aeroelastic effect of a super tall building, which exhibited significant aeroelastic effects and modal coupling during typhoon. The characteristics of wind-induced response of the model during different wind speeds were discussed. Complex mode decoupling technique and Bayesian approach were used to identify and analyze the variation of the first two modal parameters of the model with reduced wind velocity. Finally, wind tunnel test results were compared with field measurements. Results show that compared with the narrow-side windward, the cross-wind vortex-induced resonance of the model is more obvious when the model is wide-side windward. The along-wind modal frequency and damping ratio show similar variation with reduced wind velocity as cross-wind modal frequency and damping ratio. Moreover, the along-wind mode shape approaches the cross-wind mode shape at the reduced wind velocity of resonance. The peak accelerations predicted from the aeroelastic model test are in good agreement with the field measurements.

Experimental Investigation of Unsteady Aerodynamic Forces and Vortex-Induced Aeroelastic Effects of a Slender Structure in Uniform and Turbulent Flows

Slender structures are sensitive to wind loads, and aeroelastic effects during vortex-induced resonance have considerable influences on their survivability, serviceability, and habitability. However, the vortex-induced aeroelastic effects and the effects of turbulence intensity on unsteady aerodynamic forces of an aeroelastic prism remain far from been fully understood. In this study, a series of wind tunnel tests, including the pressure measurements of a rigid model and simultaneous measurements of the pressure and response of an aeroelastic model, were conducted in three different wind flows. The characteristics of unsteady aerodynamic forces and the effects of turbulence intensity on the unsteady aerodynamic forces were systematically investigated. The mechanism of aeroelastic effects and the variations of aerodynamic damping ratios were also discussed. Wind-induced responses were predicted by the unsteady aerodynamic forces and compared with the measured values. The experimental results show that vortex-induced aeroelastic effects on the wind-induced responses and the unsteady aerodynamic forces are significant. An increase in the turbulence intensity may result in a weak correlation of the unsteady aerodynamic forces and thus suppress the vortex-induced aeroelastic effects. Moreover, the amplitudes of the positive and negative peaks of the aerodynamic damping ratios decrease with the increase of the turbulence intensity. In addition, the wind-induced responses predicted by the unsteady aerodynamic forces measured from the aeroelastic model are the closest to the measured responses.

Experimental Study on Aeroelastic Instability of Spherical Inflatable Membrane Structures with a Large Rise–Span Ratio

Spherical inflatable membrane structures are extremely prone to suffer aeroelastic instability under strong winds, which requires detailed investigation. In this paper, based on the digital image correlation technology (DIC), the displacement and strain response characteristics under wind loads are investigated. Furthermore, the aeroelastic instability characteristics and the criteria for determining the occurrence of this phenomenon are defined. The results show that the top, windward, and side parts of the structure deform upward, inward, and outward. The extreme value of the total displacement occurs at approximately 1/2 of the windward region. Maximum principal strains occur at the windward and leeward centers together with the top region. After the wind speed exceeds the critical value (the dimensionless critical wind speed is observed at 1.37), the structure undergoes a sudden change of dominant vibration mode, the damping ratio decreases dramatically and reaches nearly zero. It can be concluded that the aeroelastic instability of the spherical inflatable membrane structure is caused by vortex-induced resonance and is characterized by a sudden increase in deformation and amplitude, a sudden change of the dominant vibration mode, and a rapid decay of the damping ratio. The Reynolds number after reaching the instability critical wind speed is Re > 3.1 × 105.