Suppression Of Vortex Shedding Research Articles

Robust and adaptive deep reinforcement learning for enhancing flow control around a square cylinder with varying Reynolds numbers

The present study applies a Deep Reinforcement Learning (DRL) algorithm to Active Flow Control (AFC) of a two-dimensional flow around a confined square cylinder. Specifically, the Soft Actor-Critic (SAC) algorithm is employed to modulate the flow of a pair of synthetic jets placed on the upper and lower surfaces of the confined squared cylinder in flow configurations characterized by Re of 100, 200, 300, and 400. The investigation starts with an analysis of the baseline flow in the absence of active control. It is observed that at Re = 100 and Re = 200, the vortex shedding exhibits mono-frequency characteristics. Conversely, at Re = 300 and Re = 400, the vortex shedding is dominated by multiple frequencies, which is indicative of more complex flow features. With the application of the SAC algorithm, we demonstrate the capability of DRL-based control in effectively suppressing vortex shedding, while significantly diminishing drag and fluctuations in lift. Quantitatively, the data-driven active control strategy results in a drag reduction of approximately 14.4%, 26.4%, 38.9%, and 47.0% for Re = 100, 200, 300, and 400, respectively. To understand the underlying control mechanism, we also present detailed flow field comparisons, which showcase the adaptability of DRL in devising distinct control strategies tailored to the dynamic conditions at varying Re. These findings substantiate the ability of DRL to control chaotic, multi-frequency dominated vortex shedding phenomena, underscoring the robustness of DRL in complex AFC problems.

Fluid structure interaction problem for flow past three unequal sized square cylinders at different Reynolds numbers

The flow past three square cylinders of unequal size placed in an inline arrangement is studied using the lattice Boltzmann method at different Reynolds numbers [Re = (u∞ d)/ν] within the range of Re = 120, 150, 160, 175, and 200 for various gap spacings (g = s/d), ranging from 1 to 6. This study focused on the symmetric examination of flow behavior for various gap spacing within the three unequal-sized square cylinders. The main objective of this study was to investigate the effects of Reynolds numbers and gap spacing for flow structure mechanism and vortex shedding suppression in between the gap and down-stream position of all three cylinders. Results are obtained in terms of vorticity contours visualization, drag and lift coefficients, Strouhal number, and physical parameters. In vorticity contour visualization, different flow behaviors are observed, known as flow regimes, and are named according to their characteristics, and they are (i) steady flow regime, (ii) shear layer reattachment flow regime (SLR), (iii) fully developed vortex shedding flow regime, (iv) two-row fully developed vortex shedding flow regime, and (v) fully developed irregular vortex shedding flow regime. The present study also includes a discussion on aerodynamic forces, namely the mean drag coefficient (Cdmean), root mean square of the lift coefficient (Clrms), and Strouhal numbers (St) for three cylinders with sizes d = 20, d1 = 15, and d2 = 10, respectively. The maximum value of Cdmean for the first cylinder (C1) is obtained at (Re, g) = (200, 3) that is, 1.5156, where the existing flow regime is the SLR flow regime, while for C2 and C3, the maximum Cdmean values are examined at critical flow behaviors, where the existing flow regime is a fully developed irregular vortex shedding flow regime. Negative values of Cdmean are also examined for cylinders C2 and C3 at some combinations of (Re, g), attributed to the effect of thrust. Furthermore, it is noticed that the values of Strouhal number are increased with an increment in values of gap spacing. The highest value of the Strouhal number for all three cylinders is observed for C1 at (Re, g) = (120, 5), reaching 0.1556 along with a two-row fully developed flow regime. Furthermore, it is investigated from the present problem that the position of unequal sized square cylinders strongly influenced the flow structure mechanism. The information found and discussed in this study could be effective for structure designing arrangement in the case of three square cylinders of unequal size placed in a horizontal arrangement.

Enhanced Aerodynamic Performance of a Two-Dimensional Airfoil Using Moving Boundaries

The effects of moving boundary conditions on the aerodynamic performance of a two-dimensional NACA 0012 airfoil at different angles of attack (α) in a uniform freestream at a Reynolds number of 10,000 are numerically studied. The moving boundary conditions are motivated by inviscid potential flow around the airfoil, which also satisfies the viscous equations of motion. In this study, the wall is moved at the slip velocity of the inviscid flow, or a fraction of it. These prescribed moving boundary conditions are shown to suppress vortex shedding, thus allowing the drag to go toward zero and the lift coefficient toward 2πα over a wide range of angles of attack (α≤20°) even in the separated flow regime. It is shown that moving boundary conditions are effective over a wide range of their strengths with respect to the overall power required (required to overcome aerodynamic drag and move the airfoil boundary). This power is shown to attain a minimum near the inviscid flow moving boundary condition, which is around 10% or less of the power required for the stationary boundary condition. Finally, the effectiveness of the moving boundary conditions is demonstrated for fully turbulent flow regimes at Re=6 million as well.

Flapping vortex dynamics of two coupled side-by-side flexible plates submerged in the wake of a square cylinder

The flapping vortex dynamics of two flexible plates submerged side-by-side in the wake of a square cylinder are investigated through a two-way fluid–structure interaction (FSI) simulation. The gap between the two plates can stabilize wakes, lengthen vortex formation, elongate vortices, suppress vortex shedding, and decrease hydrodynamic forces. The numerical results indicate that the two flexible plates can exhibit four distinct modes of coupled motion: out-of-phase flapping, in-phase flapping, transition flapping, and decoupled flapping, depending on the gap spacing. Additionally, it is discovered that each of the four coupling modes has a unique pattern of vortex development. The findings of this study should proved valuable in the design of FSI-based piezoelectric energy harvesters utilizing cylinder–plate systems.

Numerical Simulation of Cavitation Control around a Circular Cylinder Using Porous Surface by Volume Penalized Method

In this work, we conducted a numerical study on the cavitation flow around a circular cylinder with Re=200 and σ=1, through the implementation of a porous coating. The primary objective addressed the effectiveness of utilizing a porous surface to control cavitation. We analyzed the cavitation dynamics around the cylinder and the hydrodynamic performance at different permeability levels of the porous surfaces (K=10−12−10−10). The flow was governed by the density-based homogeneous mixture model, and the volume penalization method was used to deal with the porous layer. A high-order compact numerical method was adopted for the simulation of the cavitating flow through solving the preconditioned multiphase equations. The hydrodynamic findings demonstrated that the fluctuations in the lift coefficient decreased when the porous layer was applied. However, it is not possible to precisely express an opinion about drag because the drag coefficient may vary, either increasing or decreasing, depending on the permeability within a constant thickness of the porous layer. The results revealed that the application of a porous layer led to the effective suppression of cavitation vortex shedding. In addition, a reduction of the shedding frequency was obtained, which was accompanied by thinner and elongated vortices in the wake region of the cylinder. With the proper porous layer, the inception of the cavitation on the cylinder was suppressed, and the amplitude of pressure pulsations due to the cavitation shedding mechanism was mitigated.

On the rotation of a Savonius turbine at low Reynolds numbers subject to Kolmogorov cascade of turbulence

With an increasing demand for small energy generation in urban areas, small-scale Savonius wind turbines are growing their share rapidly. In such an environment, Savonius turbines are exposed to low mean velocity with highly turbulent flows made by complex geographies. Here, we report the flow-induced rotation of a Savonius turbine in a highly turbulent flow (18% turbulence intensity). The high turbulence is realized by using the far-field of an open-jet. Compared to low turbulence inflow (1% turbulence intensity), the turbine rotates 4% faster in high turbulence since the torque/power increases with turbulence intensity. The wake measurement by hot-wire anemometry and particle image velocimetry reveals the suppression of vortex shedding in high turbulence. In addition, a newly developed semi-empirical low-order model, which can include the effect of turbulence intensity and integral length scale, also confirms high turbulence intensity contributes to the rotation of the turbine. These results will boost more installation of small Savonius turbines in urban areas in the future.

On the omnidirectionality of a system with eight spinning rods for wake control of a circular cylinder in laminar regime

We investigate the omnidirectionality of a system comprised of a main circular cylinder (of diameter D) fitted with eight rotating rods (of diameter d=D/20) acting as wake-control devices over the incoming flow of velocity U∞ and viscosity ν. The gap between rods and main body is G/D=1/100. Finite-volume simulations were conducted at a Reynolds number Re=U∞D/ν=100 in two configurations: One in which all rods spun with the same angular velocity (case 0); and another, in which the rotation speeds were inspired by potential-flow theory (case 1). We show through analysis of hydrodynamic coefficients, vorticity contours and power consumption that both configurations reduced mean drag, eliminated the vortex wake, and were negligibly affected in terms of power loss by the angle of attack. Nevertheless, the two cases showed different behaviours regarding omnidirectionality: While case 1 became ever “more omnidirectional” (that is, less susceptible to the angle of attack to render null mean lift and suppress vortex shedding) with increasing angular speeds, case 0 produced an imbalanced, yet steady, wake that led to larger absolute values of mean lift at higher speeds. The relative importance of each rod of the system is explained, and it becomes clear that merely introducing actuating power into the rods’ motion does not translate directly into better wake control. Rather, it is essential that the rotation speeds are appropriately weighted according to the position of the rods relative to regions of boundary and shear layer, and wake of the main body.

Optimizing flow control with deep reinforcement learning: Plasma actuator placement around a square cylinder

This study introduces a deep reinforcement learning-based flow control approach to enhance the efficiency of multiple plasma actuators on a square cylinder. The research seeks to adjust the control inputs of these actuators to diminish both drag and lift forces on the cylinder, ensuring flow stability in the process. The proposed model uses a two-dimensional direct numerical simulation of flow past a square cylinder to represent the environment. The control approach involves adjusting the AC voltage across three specific configurations of the plasma actuators. Initially tested at a Reynolds number (ReD) of 100, this strategy was later applied at ReD of 180. We observed a 97% reduction in the mean drag coefficient at ReD = 100 and a 99% reduction at ReD = 180. Furthermore, the findings suggest that increasing the Reynolds number makes it harder to mitigate vortex shedding using plasma actuators on just the cylinder's rear surface. However, an optimized configuration of these actuators can fully suppress vortex shedding under the proposed control scheme.

Flow past rotating cylinders using deterministic vortex method

This study examines the performance of an in-house code based on a deterministic vortex method on circular and square cylinders rotating with constant velocity. Subjecting a bluff body to rotary about its axis effectively reduces drag forces, suppresses the fluctuating forces, and increases the lift forces (known as the Magnus effect). Rotating cylinders are well known for their use in rotor ships, rotor aircrafts, and wind turbines. This study aims to establish the accuracy of the in-house code for the rotating circle cylinders based on the results from the literature and examine the behavior of the rotating square cylinders (a less-studied case). A square section, as a many-sided shape, can be considered when the behavior of more complex geometries is of interest, such as trajectories of the sediments, or replacing circular sections when autorotation is of importance. Both cylinders are exposed to a uniform flow of Re = 200 and an imposed rotation rate range of 0 ≤ α ≤ 5.5 for the circular, and 0 ≤ α ≤ 5 for the square cylinder. The present numerical tool is able to predict the vortex shedding suppression as a result of forced rotation. For both cases, a systematic increase in the time-averaged lift coefficient (≈25.5 for the circular and ≈26 for the square case when α = 5) and a general descending trend in the time-averaged drag coefficient (≈0.03 for the circular and ≈0 for the square case when α = 5) are detected. The second mode of vortex shedding for the circular cylinder is captured within a narrow range of rotation rates. A noticeable feature of the flow over rotating square cylinders is the emergence of near-field wakes in the near-body region, which develop independently from the wake behind the body. To the best of the authors’ knowledge, this is the first comprehensive study of a rotating body carried out using a deterministic vortex method-based numerical tool.

Application of CFD on VIM of semi-submersible FOWT: A Case Study

This study examines the Vortex Induced Motions (VIM) of the INO WINDMOOR 12 MW semi-submersible Floating Offshore Wind Turbine (FOWT) platform using three-dimensional Computational Fluid Dynamics (CFD). The results from both model- and full-scale simulations are presented. The model scale results reveal varying VIM performances at different current headings, with detailed flow visualizations and analyses of hydrodynamic loads on FOWT components providing insights into the underlying wake interaction scenarios. One simulation shows bifurcated VIM, where regular motions are intermittently interrupted due to simultaneous suppression of vortex shedding on all FOWT columns. Preliminary full-scale CFD results suggest a strong scale effect. The paper concludes with a discussion on how CFD simulation can be more effectively used in VIM research.

Drag reduction of a cylinder by using spiral protuberances to generate three-dimensional surface flow

The air flow around a circular cylinder with 12 spiral protuberances was investigated via wind tunnel static force and surface pressure measurement tests to study drag reduction. A comparison with the flow characteristics of a smooth cylinder is presented herein. Kármán vortex shedding was suppressed and drag reduction of approximately 33% was observed within the Reynolds number (Re) range of 1.3×104 to 3.1×104. This drag reduction was associated with the three-dimensional surface flow caused by the guiding effect of the protuberances. The guiding effect became more significant with an increasing Re and helped delay the separation points. Therefore, upon the suppression of vortex shedding, Re dependence phased out, and instead, the flow was controlled by the spiral protuberances, and a constant dimensionless drag was achieved.

Publisher's Note: “Suppression of vortex shedding in the wake of a circular cylinder through high-frequency in-line oscillation” [Phys. Fluids 35, 073605 (2023)

Publisher's Note: “Suppression of vortex shedding in the wake of a circular cylinder through high-frequency in-line oscillation” [Phys. Fluids <b>35</b>, 073605 (2023)

A numerical study on the benefits of passive-arc plates on drag and noise reductions of a cylinder in turbulent flow

In this study, we introduce a novel arrangement consisting of two arc plates around a cylinder with the privilege of improved fluid flow and noise control. The arc plates are placed symmetrically and concentrically at the rear portion of a circular cylinder. The coverage angle (30 °≤β≤75°) of the plates and the normalized radius of arc plates (1.125≤Rd≤1.625) are varied to find the optimum case in terms of drag and noise reductions. The simulations are performed for a turbulent flow with a Reynolds number of 22 000. The numerical analysis is based on an unsteady Reynolds-averaged Navier–Stokes (URANS) solver and Ffowcs Williams and Hawkings (FW–H) acoustic analogy. It is found that by implementing the arc plates, the noise level and drag coefficient decrease dramatically. The results also reveal a strong correlation between the vortex shedding suppression and the noise reduction. It is shown that as the fluctuation of lift force decreases, the performance of flow and noise control enhances simultaneously. Furthermore, the noise assessment indicates that in a specific configuration of the arc plates, the overall sound pressure level decreases by around 51 dB compared to the uncontrolled case with no arc plates. Also, a maximum noise reduction of 27 dB is achieved, in which the drag coefficient reduces by 39% compared to the case with no arc plates. In conclusion, the results provide strong support for the proposed passive method as a beneficial strategy for noise reduction and wake control of cylindrical structures, which have wide applications in industry.

Numerical Assessment of Flow Energy Harvesting Potential in a Micro-Channel

A micro-energy harvesting device proposed in the literature was numerically studied. It consists of two bluff bodies in a micro-channel and a flexible diaphragm at its upper wall. Vortex shedding behind bodies induces pressure fluctuation causing vibration of the diaphragm that converts mechanical energy to electrical by means of a piezoelectric membrane. Research on enhancing vortex shedding was justified due to the low power output of the device. The amplitude and frequency of the unsteady pressure fluctuation on the diaphragm were numerically predicted. The vortex shedding severity was mainly assessed in terms of pressure amplitude. The CFD model set-up was described in detail, and appropriate metrics to assess the energy harvesting potential were defined. Several 2D cases were simulated to study the effect of the inlet Reynolds number and channel blockage ratio on the prospective performance of the device. Furthermore, the critical blockage ratio leading to the vortex shedding suppression was sought. A higher inlet velocity for a constant blockage ratio was found to enhance vortex shedding and the pressure drop. Great blockage ratio values but lower than the critical ones seemed to provide great pressure amplitudes at the expense of a moderate pressure drop. There is evidence that the field is fruitful for further research and relevant directions were provided.

Pressure coherence and flow structure of a twisted elliptical cylinder at moderate Reynolds number

In this study, we performed an experimental study to explore the surface pressures and flow structures around twisted elliptic (TE) cylinders at a Reynolds number of 3.8 × 104. Two TE cylinders, denoted as TE11 and TE12, with aspect ratios of 1.1 and 1.2 for elliptical cross-sections, respectively, were selected to compare the performance of vortex shedding suppression. The distribution characteristics of the fluctuating pressure at different spanwise positions and the phase difference and coherence function between the pressure signals were analyzed. The results showed that TE12 cylinder was not dominated by antiphase shedding vortices, as in the baseline and TE11 cylinders, but rather by low-frequency components in the flow field, yielding a Gaussian distribution of the fluctuating pressure. The pressure pulsations were significantly asymmetric for the TE12 cylinder due to the earlier flow separation on the upper surface, but this asymmetry was not apparent for the TE11 cylinder. The Reynolds shear stress distribution revealed that the transition to turbulence in the separated layer was significantly delayed by the TE surface. Moreover, for TE12 cylinder, zero turbulence fluctuations in the near wake explained the low-frequency domination of the pressure fluctuations, resulting in 93.8% attenuation of the lift fluctuations.

Suppression of vortex shedding in the wake of a circular cylinder through high-frequency in-line oscillation

This paper presents a new flow control approach to suppress the vortex shedding in the wake of a circular cylinder through high-frequency oscillation. The circular cylinder is forced to oscillate in the streamwise direction at high-frequency and low amplitude, corresponding to a high Stokes number (β = 100–1000) and low Keulegan–Carpenter number (KC = 0.001–4). Two-dimensional (2-D) and three-dimensional (3-D) direct numerical simulations of an oscillating circular cylinder in steady current have been carried out in the parameter space of KC, Rec, and β. Our numerical results show that when the flow remains in the two-dimensional vortex shedding regime, the cylinder wake sequentially experiences transitions from the vortex shedding regime to the suppression of the vortex shedding regime and finally to the symmetry breaking regime, with increasing KC. Corresponding wake characteristics and variations of hydrodynamic forces over the three wake regimes are explored. Three quantities that represent shear-layer characteristics, including the length of separating shear layers, the circulation of shear layers and wake recirculation length, reach maxima at the onset of suppression. The physical mechanisms for the suppression of vortex shedding and occurrence of symmetry breaking are also explained. Once the flow becomes 3-D, vortex shedding from the cylinder cannot be suppressed, primarily because the outer shear layers induced by the steady approaching flow are enhanced in 3-D flows. The cylinder oscillation over the frequency range investigated in the present study delays wake transition to 3-D. The cylinder oscillation alters the 3-D vortical structure and its spanwise wavelength significantly.

Numerical investigation of cylinder vortex-induced vibration with downstream plate for vibration suppression and energy harvesting

The effect of the downstream plate on the vortex-induced vibration (VIV) of the cylinder is numerically studied for the first time by using the fluid-structure interaction method. The influences of the plate height (H) and the gap length (G) between the plate and the cylinder on the cylinder dynamic characteristics are investigated. The main conclusions can be summarized as follows: (1) Cylinder will first be converted from VIV to galloping and then reverted to the classical VIV response with the increasing gap length and the plate height. (2) Under the plate interference, the switch of the wake vortex shedding mode from “2S” to “P + S″, the increase in lift odd harmonic components and amplitude, and the decrease of the phase difference between lift and displacement are the essential reasons for the enhanced vibration. (3) In the optimal galloping state (G = 0.5 D, H = 0.5 D), the cylinder amplitude and lock-in range are increased by 670.8% and 473% compared to that of the isolated cylinder system, respectively, which is beneficial to energy harvesting. (4) The reattachment flow appearance and cylinder wake vortex-shedding suppression induced by the high plate, are the deep reasons for the vibration weakening. In this case, the lift force and vortex-shedding frequency are greatly reduced, while the lock-in interval is delayed or even eliminated. (5) When H = 3.0 D and G = 0.5 D, the lock-in interval is 100% cleared, and the vibration intensity of the cylinder is reduced by 84.4%. (6) The feasibility of utilizing the square plate for flow-induced vibration control of non-cylindrical bluff bodies is verified for the first time. Overall, the above results are of great significance for optimizing structural vibration control and vortex sensing technology based on VIV suppression, as well as energy harvesting aiming at enhancing vibration.

Vortex shedding characteristics and hydrodynamic forces of stationary and elastically mounted side-by-side cylinders fitted with small diameter control rods

Vortex shedding behind bluff bodies can induce noise and vibration problems when it engages in a feedback cycle of oscillations with an acoustic or structural mode. Therefore, several passive and active flow control techniques have been developed to suppress vortex shedding behind a single bluff body. However, less attention was given to the case of multiple bluff bodies in cross-flow. Therefore, in this paper, a numerical investigation is performed to study the effect of adding small diameter control rods in the vicinity of two side-by-side cylinders on the vortex shedding characteristics, the hydrodynamic fluid forces, as well as the suppression of vortex-induced vibration. The simulations are conducted at a Reynolds number of Re = 200 and the side-by-side cylinders have a spacing ratio of T∗=2.5. The number of control rods and their angular positions around the main cylinders are varied. Fitting the side-by-side cylinders with control rods has resulted in three different flow regimes compared to the base case with no control rods. These flow regimes depend on the angular positions of the control rods and they are classified as; bistable flow, stable biased flow, and merged wake flow regimes. The stable biased flow regime has resulted in the maximum reduction of the fluctuating lift coefficient of the side-by-side cylinders, especially when the control rods are placed at θ=135° from the flow stagnation point. Increasing the number of control rods around the cylinders has further reduced the fluctuating lift coefficient and produced a more symmetric wake at the rod angles which produce the stable biased flow, and the merged wake flow regimes. The vortex-induced vibration of the side-by-side cylinders is investigated when the control rods are placed at the angular position that results in a stable biased flow regime. It is revealed that fitting the cylinders with control rods at an angular position of θ=135° has resulted in reducing the vibration amplitude over the whole range of the simulated reduced flow velocities, which makes this technique a viable one to control the vortex shedding and the vortex-induced vibration of side-by-side cylinders.

Flow-induced vibration (FIV) fatigue damage characteristics of two unequal-diameter flexible cylinders in a staggered arrangement

In offshore engineering, fatigue damage caused by flow-induced vibrations (FIVs) presents a considerable and potential threat to flexible cylindrical systems during their service lifetime. Through FIV experiments, this paper estimates and analyzes the fatigue damage of two unequal-diameter cylinders with diameter ratio d/D = 0.5 (where d and D denote the diameter of small and large cylinders) and the center-to-center spacing ratio P/d = 6 (where P denotes the center-to-center distance between two cylinders) through the S–N curve and fatigue damage accumulation methods in the DNV standard. Ten staggered configurations were studied, including two relative positions and five stagger angles (θ = 15°, 30°, 45°, 60°, and 75°). The fatigue damage evaluation results indicate that the FIV fatigue damage is highly affected by the stagger angle and relative position of the two cylinders. The FIV fatigue behavior of the two unequal-diameter cylinders is quite different from that of the two identical cylinders. When the large cylinder is located upstream, its wake shielding effect on the small cylinder is predominant at small stagger angles, so both the IL and CF fatigue damage of the downstream small cylinder is significantly suppressed, especially when Vr ≤ 16.28. But as the stagger angle is increased, the wake-induced flutter can aggravate the fatigue damage of the downstream small cylinder. Moreover, the CF fatigue damage of the large cylinder is decreased at small angles due to the vortex-shedding frequency suppression of the small cylinder and the fatigue damage of the large cylinder in the IL direction is analogous to that of the isolated cylinder and is negligibly affected by the small cylinder. When the small cylinder is located upstream, the IL FIV fatigue damage of the downstream large cylinder is approximately unaffected due to the narrow wake of the small cylinder. However, the CF fatigue damage of the large cylinder is greatly reduced at small stagger angles.

Visualization and Parametric Study on Vortex Shedding Suppression of Cylindrical Structures in Offshore Engineering Using Large Eddy Simulation

Cylindrical structures are widely used in offshore and marine engineering, but they may suffer from vortex-induced vibration under the influence of ocean or wave currents, which can lead to severe fatigue damage. In this study, we applied the open-source software Open-Source Field Operation and Manipulation (OpenFOAM) to investigate the characteristics of fluid flow around offshore cylindrical structures, taking into account the effect of helical strake parameters, such as pitch and strake number. The aim of this study is to explore the possibility of suppressing vortex shedding with different helical strake parameters. Numerical simulation results demonstrated that attaching a helical strake to the bare cylinder destroyed vortex shedding in offshore cylindrical structures. The vortex visualization showed that the helical strake destroyed the three-dimensional vortex structures. Moreover, the lift coefficient data showed that the vibration frequency of the cylinder decreased after attaching the helical strake, indicating that the vortex-induced vibrations on the wake flow tended to fade. The results suggest that the helical strake is a promising option for suppressing the wake vortex shedding of cylindrical structures in offshore engineering.