Vortex-induced Vibration Characteristics Research Articles

Numerical simulation of the vortex-induced vibrations of a 4:1 rectangular cylinder subjected to yaw uniform currents

The practical engineering structures are not always perpendicular to the wind but often in skew positions. This yawed configuration may lead to more complex three-dimensional flow characteristics and different vortex-induced vibration (VIV) responses. However, the related study is very inadequate. Therefore, comprehensive numerical investigations of the VIV characteristics of a 4:1 rectangular cylinder have been conducted using the three-dimensional (3D) Large-Eddy Simulation (LES) at five different yaw angles (β = 0°, 5°, 10°, 20°, 30°). An innovative method for creating 3D meshes was introduced, demonstrating a good agreement with the experimental results while significantly reducing the mesh number, and consequently the computation time. The VIV response, pressure distribution, aerodynamic force, flow field, and energy input/output were analyzed for various yaw angles. The results demonstrate that the periodic boundary conditions on the spanwise domain side is more reliable than those of the wall boundary conditions. The velocity component parallel to the cylinder axis can be ignored in the analysis of elastically-mounted rectangular rigid cylinders for β up to 30°. If only considering the perpendicular axis velocity component, the amplitudes and lock-in regions for β = 5°, 10°, 20°, and 30° are highly consistent with those of β = 0°, which have effectively validated the accuracy of Independence Principle in evaluating the VIV of a 4:1 rectangular cylinder.

Study on the vortex-induced vibration and flow control of ribbed circular cylinder

This work investigates the vortex suppression performance and mechanism of ribs on high-quality ratio cylinders. Through wind tunnel tests and numerical simulations, the surface wind pressure distribution characteristics and flow separation phenomena of different ribbed cylinders are explored, and the spanwise correlation and nonlinear vibration characteristics of vortex-induced vibrations of ribbed cylinder models are analyzed. The main conclusions are as follows: ribs change the position of the boundary layer separation point, and the difference in size of left and right separated vortices causes a pressure jump phenomenon, altering the wind pressure distribution of the segment model and reducing the wind pressure, resulting in an increase in the locked wind speed of the ribbed cylinder. Complex separated vortices form behind the ribs, affecting the size of the wake vortex and reducing the stability of the segment model at locked wind speeds. Cylinders with four ribs exhibit good vortex-induced vibration suppression performance at 0° and 45° positioning angles. In addition, the cylinder with four installed ribs cylinders exhibits two locked wind speed regions, each showing different motion states: at the primary locked wind speed, they mainly demonstrate quasi-periodic vibrations and degraded quasi-periodic vibrations, while at the secondary locked wind speed, primarily in a chaotic state dominated by high-frequency harmonic components. These research findings have significant implications for future studies and practical engineering applications.

Robust damping improvement against the vortex-induced vibration in flexible bridges using multiple tuned mass damper inerters

The tuned mass damper inerter (TMDI) is considered as one of countermeasures to mitigate the very-low-frequency vertical bending vortex-induced vibration (VIV) in flexible bridges. However, the control robustness of the TMDI against the system uncertainty is a serious concern due to the limited inerter span capacity. In this paper, the multiple tuned mass damper inerter (MTMDI) is used instead of identical TMDIs to provide a robust equivalent damping ratio against the uncertain VIV within the entire lock-in wind speed range. A design framework of the MTMDI considering the inerter span length is proposed based on a universal VIV model suitable for the fully closed, centrally slotted, and semi-closed box decks. In the framework, the fluctuation of VIV characteristics with the wind speed, the probability of occurrence of the VIV, and the uncertainties in VIV characteristics and deck dynamics are considered, simultaneously. Two objection functions are defined to focus on the maximizing the equivalent damper ratio and reducing the VIV mitigation failure, respectively. Finally, numerical analysis of a flexible bridge-MTMDI system subjected to the VIV is performed. The results show that the wind speed probability distribution plays a role of weighting coefficient in the MTMDI optimization. The choice of the objective function depends on the mass ratio of the MTMDI and the level of the system uncertainty. The well-optimized MTMDI achieved a more robust control result than the TMDI within the entire lock-in wind speed range.

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.

Dynamic analysis of a drilling string for deepwater riserless drilling with vortex-induced vibration considered

Riserless drilling will become the mainstream technology for deepwater drilling in the future owing to its operational characteristics. At present, researchers only analyze the seawater section or formation section but do not analyze the whole drill string to study the dynamics of riserless drilling. In fact, the ocean load affects not only the vortex-induced vibration characteristics of the drill string in seawater but also the load distribution of the drill string in the formation. Ignoring the formation or ocean load will lead to inaccurate prediction results. On this basis, in addition to the traditional drilling string boundary condition of seawater and formation, a new boundary condition of drilling string at mud line for riserless drilling is proposed. Considering vortex-induced vibration, a full-well drilling string dynamic model without riser drilling is established by the finite element method, and the dynamic characteristics of the full-well drilling string under multiple loads are analyzed. In addition, the effects of WOB, surface flow rate, and drilling fluid density on the dynamics of riserless drilling string in seawater and formation sections are discussed. This study provides theoretical guidance for the safety of riserless drilling in complex marine environments.

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.

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.

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.

Vortex-induced vibration characteristics of three cylinders with isosceles-triangle arrangements at low Reynolds number

The geometric factors of multi-cylinders are one of the factors affecting the efficient energy capture of vortex-induced vibration aquatic clean energy. Based on the computational fluid dynamics numerical simulation method and overset mesh technology, an efficient dynamic model of VIV (vortex-induced vibration) of two-dimensional elastic-supported cylinders was established. The influence of different vertex angles on the VIV characteristics in the isosceles-triangle arrangement was investigated. The results show that the upstream cylinder is less affected by the vertex-angle, and the peak value moves to the left in the α-A*y curve of the downstream cylinders. As α increases, the upstream cylinder moves in an 8 shape and moves in the negative direction of the flow direction, while the downstream cylinders move in an O shape and gradually become narrow. The vortex shedding mode of downstream cylinders is mostly the P + S mode, and its amplitude is related to the position of the upstream cylinder's wake vortex effect. The lift and drag coefficients of the downstream cylinders are affected by α, while the dominant frequency of vibration is independent of the change in α and is greatly affected by Re. With the increase in Re, the positive correlation between the lift coefficient and transverse displacement gradually weakens.

Study on Vortex-Induced Vibration Response of Riser under the Action of Oscillating Flow Superposition

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

Vortex-induced vibration characteristics of mining riser under the coupling effect of external ocean current and internal multiphase flow

As an important equipment for deep-sea oil and gas development, riser is prone to failure due to external ocean environmental load and internal fluid in the process of oil and gas exploitation. In this paper, a dynamic analysis model of the riser system under the action of internal and external flow coupling is established. This model is discretized by using the finite element method and solved by Newmark-β method. The vortex-induced vibration characteristics of the mining riser under the action of internal and external flow coupling are analyzed. Results show that compared with the traditional riser containing pure liquid flow, gas–liquid two-phase flow in pipe can reduce the natural frequency of the riser and increase the vibration amplitude and frequency. The natural and vibration response frequencies of the riser decrease with the increase in the discharge rate and the density of the two-phase mixture, and the modal response remains unchanged. With the increase in the air inlet ratio, the natural frequency of the riser decreases, but the vibration frequency increases, and induces the vibration of higher modes of the riser.

A novel vortex-induced vibration model for a circular cylinder in the vicinity of a plane wall

A novel vortex-induced vibration (VIV) model is proposed to predict the transverse responses of an elastically mounted circular cylinder in the proximity of the wall. Firstly, flow characteristics and hydrodynamic loads on a near-wall stationary circular cylinder are summarized and analyzed based on the existing experimental results, and then the Strouhal shedding frequency and the empirical correlations of the mean lift coefficient and oscillating lift coefficient are established. Subsequently, by introducing the empirical correlations of fluid loads to the equations of structure vibration, a novel VIV model for the near-wall circular cylinder is proposed to describe more precisely the effect of the plane wall. The accuracy, stability, and adaptability are validated by employing experimental VIV results. Compared to existing models, the novel model has advantages in achieving acceptable accuracy in various scenarios. Finally, using the proposed VIV model, the dynamic features of a near-wall circular cylinder to the reduced velocity and gap ratio are studied in detail, including the time-averaged displacements, lock-in regime, maximum amplitude, and dominant frequency. The results obtained are valuable for understanding the VIV characteristics of the near-wall cylinder, and the semi-empirical VIV model proposed could be applied in engineering prediction in the future.

Nonlinear vortex-induced vibration of wind turbine towers: Theory and experimental validation

Vortex-induced vibration (VIV) of wind turbine tower is a common occurrence in practical engineering, significantly impacting the safety and reliability of structure. An effective method is developed to investigate the VIV characteristics of a wind turbine tower with an elastic foundation and a lumped mass. To simulate the fluid–structure interaction, the van der Pol equation is utilized. The equations of motion of wind turbine tower, accounting for aerodynamic force, are established using Hamilton’s principle and the assumed mode method, and they are solved by the method of multiple scales. Modal functions of the wind turbine tower are obtained through the finite element method (FEM). The analysis further explores the influences of various parameters on the VIV characteristics of wind turbine tower. The results show that the VIV occurs within the frequency lock-in and multi-value ranges, and the critical wind speeds are mainly determined by the diameters of the segments near the tower top. Moreover, as the lumped mass increases or the foundation stiffness decreases, the occurrence of VIV shifts to lower wind speeds. A wind tunnel experiment of a scaled wind turbine tower model validates the frequency lock-in range of the VIV analysis results.

Numerical investigation on VIV of a circular cylinder with multiple small control rods

This study conducts a numerical simulation of the two-degree-of-freedom vortex-induced vibration (VIV) for a circular cylinder attached to multiple small control rods. It systematically investigates the effects of control rod number n, attack angle α, and gap ratio G/D on the vibration responses of the main cylinder. The control rod arrangements are classified into symmetric and asymmetric configurations based on the attack angle variation. The 5, 7, and 9 small control rods present similar impacts on the VIV's characteristics of the circular cylinder. The VIV of the main cylinder is significantly suppressed by the odd number of small control rods in two regions. The 1st excellent VIV suppression (EVS) region locates in the gap ratio of G/D=(0.2, 0.3) for all attack angles. The 2nd EVS region is within a wide range of gap ratios at the 2nd symmetric configuration. The nine control rods at G/D = 1.4–1.5 in the 2nd EVS region can completely suppress the circular cylinder VIV. Meanwhile, the flow structure of the cylinder group is fully symmetric, and vortex shedding cannot be formed behind any circular cylinders.

Numerical Investigation on Drag and Vortex Induced Vibration Characteristics of Multiple Cylinders

The drag and vortex induced vibration (VIV) characteristics of a multiple cylinder are investigated using the detached eddy simulations. The multiple cylinders consist of a single main cylinder and twin auxiliary cylinders for a deep sea mining riser. Tandem and side-by-side arrangements are tested and compared with the single cylinder. The drag characteristics are investigated with the stationary case in the range of 0.5∼2.0 × 105 in Reynolds number (Re). The drag of the tandem arrangement shows smaller drag than those of the single cylinder while it’s consisted with the three cylinders. The stationary vortexes are observed at the clearance between the main and auxiliary cylinder which make the tandem arrangement become airfoil-like section as a total which induce the smallest drag than the other cases. The VIV characteristics are studied with the cases of forced oscillation in the cross-flow direction. The damping and added mass coefficients in cross-flow direction are estimated from the time series of the lift forces. Flow field analysis reveal the difference in VIV characteristics due to the variety of the arrangements and the single pipe.

Investigation on Numerical Simulation of VIV of Deep-Sea Flexible Risers

The vortex-induced vibration (VIV) of flexible risers is a complex fluid–structure interaction (FSI) phenomenon. In this study, we conducted a numerical simulation method based on the slicing method to study the vortex-induced vibration (VIV) of deep-sea flexible risers with different slenderness ratios and uniform flow velocities. The method combines the finite element model of the riser structure with the two-dimensional flow field slices solved by the Fluent solver. The fluid–structure interaction was realized by a self-compiled UDF program and the overset mesh technique. The numerical results were validated by comparing them with experimental data. The VIV characteristics of the riser, such as the vibration track, vibration mode, vibration frequency and wake vortex shedding mode, were analyzed. The article reveals the nonlinear dynamic features of flexible riser vibration, such as multi-frequency vibration, wide-frequency vibration and multi-modal vibration. The article also provides insights into the fluid–structure interaction mechanism of VIV of deep-sea flexible risers.

Numerical analysis of reverse wake-induced vibration at low Reynolds number

Reverse wake-induced vibration (RWIV) of two tandem cylinders with the downstream one fixed is numerically studied in this paper; Reynolds number is set as 150 (Re = 150). The effect of different spacing ratios (α) ranging from 3 to 6 with a gap of 0.5 is simulated to investigate the vibration characteristics of RWIV, where the spacing ratio (α) is defined as the nondimensional ratio of the center-to-center separation between the cylinders. As the spacing ratio increases from 3 to 6, RWIV shows a transition from galloping to vortex-induced vibration (VIV), which is also a reverse phenomenon compared to wake-induced vibration (WIV). As to the wake mode, two different types of vortex motion (2S - 2P - 2S and 2S - 2P) are observed within the given range of spacing ratio. Empirical modal decomposition is also applied to further analyze the vibration characteristics of galloping and VIV in RWIV. When the system shows galloping, the number of decomposed modes is larger with the increasing reduced velocity, and different vibration modes show evident mutual anisotropy. In addition, the vortex line diagram is used to analyze the wake vortex characteristics of the RWIV and to supplement the above findings.

Experimental investigation on vortex-induced vibration characteristics of a segmented free-hanging flexible riser

Different from the traditional marine riser, the vertical lifting pipeline in the deep-sea mining system can be regarded as a free-hanging flexible riser with an unconstrained bottom end. Likewise, problems in terms of vortex-induced vibration (VIV) and flexible deformations can arise during operation. This paper presents experimental tests on a segmented free-hanging marine riser used for deep-sea mining, focusing on the vortex-induced vibration. The riser was formed by connecting pipe sections using flanges, with the top fixed and a lumped mass block added at the bottom to simulate the lifting pump and buffer station, resulting in weakly constrained boundary conditions. By employing the modal superposition principle and the wavelet time-frequency method, we comprehensively investigated the response characteristics of the typical pipe sections and the coupled oscillation of the riser's vibration modes. During the experiment, two important phenomena that differed from previous VIV tests were observed. Firstly, at low reduced velocities (Ur ≤ 7.77), the dominant frequency no longer conformed to the doubling principle in both directions but remained consistent. Secondly, the weak constraint effect of the concentration of mass at the bottom disrupts the formation of vortex shedding, thereby reducing the bending response of the CF direction of the bottom pipe sections. Meanwhile, the drag force enhances the bending response of the IL direction. Additionally, the middle and bottom pipe sections of the riser exhibited obvious mode competition, with the dominant mode often followed by several subordinate modes with considerable vibration energy.

Investigation of Vortex-Induced Vibration of Double-Deck Truss Girder with Aerodynamic Mitigation Measures

The long-span double-deck truss girder bridge has become a recommend structural form because of its good performance on traffic capacity. However, the vortex-induced vibration (VIV) characteristics for double-deck truss girders are more complicated and there is a lack of related research. In this research, wind tunnel tests were utilized to investigate the VIV characteristics of a large-span double-deck truss girder bridge. Meanwhile, the VIV suppression effect of the aerodynamic mitigation measures was measured. Furthermore, the VIV suppression mechanism was studied from the perspective of vortex shedding characteristics. The results indicated that the double-deck truss girder had a significant VIV when the wind attack angles were +3° and +5°. The aerodynamic mitigation measures had an influence on the VIV response of the double-deck truss girder. The upper chord fairing and lower chord inverted L-shaped deflector plate played a crucial role in suppressing VIV. Numerical analysis indicated that vortex shedding above the upper deck or in the wake region may dominate vertical VIV, while vortex shedding in the wake region of the lower deck may dominate torsional VIV. The upper chord fairing and lower chord inverted L-shaped deflector plate disrupted the original vortex shedding pattern in both regions, thereby suppressing VIV. This research can provide a foundation for bridge design and vibration suppression measures for large-span double-deck truss girder bridges.

Piezoelectric energy extraction from a cylinder undergoing vortex-induced vibration using internal resonance

A novel concept of utilizing the kinetic energy from ocean currents/wind by means of internal resonance is proposed to address the increasing global energy demand by generating clean and sustainable power. In this work, a non-linear rotative gravity pendulum is employed to autoparametrically excite the elastically mounted cylinder for a wide range of flow velocities. This concept is adopted to increase the oscillation amplitude of the cylinder due to vortex-induced vibration (VIV) in the de-synchronized region for energy harvesting. In this regard, a VIV-based energy harvesting device is proposed that consists of a cylinder with an attached pendulum, and energy is harvested with bottom-mounted piezoelectric transducers. The cylinder undergoes VIV when it is subjected to fluid flow and this excites the coupled fluid-multibody cylinder-pendulum system autoparametrically. In the de-synchronized region, when the vortex shedding frequency becomes two times the natural frequency of the pendulum, an internal resonance occurs. This helps in achieving a higher oscillation amplitude of the cylinder which does not happen otherwise. This study is focused on the two degree-of-freedom (2-DoF) cylinder-pendulum system where the cylinder is free to exhibit cross-flow vortex-induced vibrations subjected to the fluid. The objective of this work is to numerically investigate the effect of a non-linear rotative gravity pendulum (NRGP) on the VIV characteristics and piezoelectric efficiency of the system. The numerical model is based on the wake-oscillator model coupled with the piezoelectric constitutive equation. The influence of the frequency ratio, mass ratio, torsional damping ratio, and ratio of cylinder diameter to pendulum length of the NRGP device on response characteristics due to VIV is also investigated. A detailed comparative analysis in terms of electric tension and efficiency is performed numerically for flows with a wide range of reduced velocities for the cylinder with and without NRGP. A comprehensive study on the implications of internal resonance between the pendulum and a cylinder undergoing VIV on generated electric tension is also reported.