Vortex Induced Vibration Energy Research Articles

Ocean energy harvester based on piezoelectric VIV using different oscillators

A finite element fluid-solid coupling model for ocean energy harvester based on piezoelectric vortex-induced vibration(VIV) is established. Given that the Karman Vortex Street is generated after the fluid passes through the vibrator. The model includes the conversion of water flow energy to VIV energy and the capture of electrical energy by piezoelectric devices. And the output voltage curve is obtained by coupling with piezoelectric beam. Based on the fluid-solid coupling calculation, the dynamic response characteristics of the oscillator under different parameters such as shape of oscillators and fluid velocity are studied. The voltage output of piezoelectric beam in cylindrical, semi-cylindrical and regular triangular oscillators is analyzed. Simulation results show that the output voltage and pressure difference are largest in regular triangular oscillator system compared with the cylindrical and semi-cylindrical system. When changing fluid velocity, it is found that the higher the velocity of the water fluid be, the higher the output voltage be. When the given fluid velocity reaches 1 m/s, the maximum output voltage of cylindrical, semi-cylindrical and regular triangular piezoelectric energy harvesters reaches 0.045V, 0.08V, and 0.085V respectively. Under the same fluid velocity, change the ratio of height and width of oscillator, and find that the higher ratio of height and width of oscillator is more suitable to harvest the energy of VIV.

Regenerative semi-active vortex-induced vibration control of elastic circular cylinder considering the effects of capacitance value and control parameters

A regenerative semi-active control system based on self-tuning Fuzzy proportional-derivative (PD) control strategy is applied to suppress the vortex-induced vibrations (VIV) of an elastically supported circular cylinder at low Reynolds numbers. Of particular interest was the effect of control parameter and capacitance on the VIV reduction and energy regeneration capabilities of adopted semi-active control system. A collaborative simulation which couples a Fuzzy PD controller along with the adjustable electromagnetic (EM) damper and corresponding energy harvesting circuit (implemented in MATLAB/Simulink) to the computational fluid dynamic (CFD) plant model (implemented in Fluent) is employed. It appears that the cylinder displacement amplitude, capacitor charging speed, and maximum stored electrical energy vary with the controller parameters and capacitance value. It is shown that the selected regenerative semiactive control system can store maximum energy in a capacitor in prescribed limiting time, along with the highest level of cylinder oscillation reduction which is the primary goal of current work.

Numerical investigation on VIV energy harvesting of four cylinders in close staggered formation

Marine hydrokinetic energy in ocean currents can be harvested using Vortex Induced Vibration (VIV). The purpose of this paper is to investigate the VIV energy harvesting and maximize the power-to-volume density by arranging four staggered cylinders reasonably. Consequently, the effect of spacing between the cylinders is the focus considered throughout this paper. The in-flow spacing X varies from 1.2D to 10.0D, where D is the Diameter of the cylinder; the transverse spacing Y varies from 2.0D to 8.0D. A series of numerical simulations are conducted using two-dimensional Reynolds-Averaged Navier-Stokes equations in conjunction with the k-ω SST turbulence model. Results indicate that the interference between the tandem cylinders is stronger than between the side-by-side arranged cylinders. The multi-cylinder interference is divided into three regions: Synchronization Region, Blocking/Encouraged Region and Recovery Region. Interaction effects can induce much more vigorous VIV response of the downstream cylinder in Encouraged Region, where the maximum converted power ratio reaches up to 3.9 with in-flow spacing X of 2.0D and transverse spacing Y of 4.0D. Moreover, the average power-to-volume density will keep increasing as the spacing X decreases if there are no other physical limitations. These results lead the way for future layout optimization of multiple cylinders.

Dual serial vortex-induced energy harvesting system for enhanced energy harvesting

This paper presents a novel dual serial vortex-induced vibration energy harvesting system for enhanced energy harvesting. It consists of two identical cantilever-based piezoelectric vortex-induced vibration energy harvesters, which are successively installed in one plane (which is paralleled with the wind flow direction) of the wind tunnel. The Lattice Boltzmann method is employed to predict the strength of vortex-induced vibrations and the pressure distribution around the circular cylinders of the harvesters. The numerical results qualitatively explain the influence of the space distance on the energy harvesting performance of the presented system. Experimental results verify the numerical analysis and demonstrate a higher energy harvesting efficiency of the presented system over its traditional single harvester. In detail, experimental results indicate that the effective wind speed range and the output power area of a coupled harvester in the presented system can be as many as 2.67 times and 6.79 times of that of the traditional single harvester, respectively.

Numerical Investigation on the Vortex-Induced Vibration of a Flexible Plate behind a Circular Cylinder

Wang, H.; Zhai, Q.; Hou, J., and Xia, L., 2018. Numerical investigation on the vortex-induced vibration of a flexible plate behind a circular cylinder. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1326–1330. Coconut Creek (Florida), ISSN 0749-0208.Vortex-induced vibration (VIV) of piezoelectric cantilever plate can convert the kinetic energy of flow into electricity effectively, and this technique has become a new research focus in the field of ocean energy harvesting and utilization over the past few years. It is known that the lock-in effect existing in VIV phenomenon can significantly broaden the structural resonance region, and improve the flow energy harvesting efficiency. The present study aims to investigate the VIV responses of a flexible plate located in the wake of a circular cylinder using a strongly coupled finite element model. Numerical simulations are conducted for two typical plate lengths (L/D = 2.0, 4.0; D is the cylinder diameter) within a wide range of gap spacings 0.5 ≤ S/D ≤ 4.0. Generally, the results show that with the increase of gap spacing, the gap flow pattern changes from vortex suppression state to vortex shedding state. For L/D = 2.0, “soft” lock-in occurs all through the examined gap spacing range, among which the plate vibrates with significant amplitude. For L/D = 4.0, the lock-in region is found to be S/D ≤ 2.0, characterized by large-amplitude resonance and vortex suppression in the gap; however, with the appearance of the gap vortex shedding, the vibration becomes negligible at S/D ≥ 2.5. The pressure distribution of fluid along the upper and lower sides of the plate is analyzed to reveal the dynamic coupling mechanism between the flow and plate. This study will provide useful theoretical reference for optimum design of the VIV energy harvesting device.

Numerical Investigation on Vortex-Induced Vibration Energy Extraction Efficiency of Double Circular Cylinders In Tandem Arrangement at Low Reynolds Number

Vortex shedding from a bluff body results in fluctuating forces acting on the bluff body, which may induce vibration of the bluff body when the bluff body is elastically mounted or deformable. Researchers put forward an idea that we can ex-tract energy from the water flow based on VIV at low flow velocity. Although plenty of researches on parameters of VIV are already presented, however, the improvement of energy extraction efficiency still needs further study. According to the previous research, this essay has simulated flow-induced vibration of tandem double circular cylinders when Reynolds number is 100. Working condition has been considered as the fixed upstream cylinder and the free vibration of the downstream cylinder. The influence of the mass coefficient and the two cylinders spacing ratio on the downstream cylinder’s energy obtained from the fluid is studied. Analysis results show that, the maximum value of the energy extraction efficiency is before the frequency locked range. In the case of large spacing ratio (L/D=7~9), the phenomenon of "beat vibration" appears on the downstream cylinder. The results of this work could provide reference for the improvement of energy extraction efficiency and the design of VIV converter.

Enhancement of Energy Harvesting Performance by a Coupled Bluff Splitter Body and PVEH Plate through Vortex Induced Vibration near Resonance

Inspired by vortex induced vibration energy harvesting development as a new source of renewable energy, a T-shaped design vibration energy harvester is introduced with the aim of enhancing its performance through vortex induced vibration at near resonance conditions. The T-shaped structural model designed consists of a fixed boundary aluminum bluff splitter body coupled with a cantilever piezoelectric vibration energy harvesters (PVEH) plate model which is a piezoelectric bimorph plate made of a brass plate sandwiched between 2 lead zirconate titanate (PZT) plates. A 3-dimensional Fluid-Structure Interaction simulation analysis is carried out with Reynolds Stress Turbulence Model under wind speed of 7, 10, 12, 14, 16, 18, 19, 20, 22.5, and 25 m/s. The results showed that with 19 m/s wind speed, the model generates 75.758 Hz of vortex frequency near to the structural model’s natural frequency of 76.9 Hz. Resonance lock-in therefore occurred, generating a maximum displacement amplitude of 2.09 mm or a 49.76% increment relatively in vibrational amplitude. Under the effect of resonance at the PVEH plate’s fundamental natural frequency, it is able to generate the largest normalized power of 13.44 mW/cm3g2.

Numerical and experimental investigation of nonlinear vortex induced vibration energy converters

In this paper, effects of bi-stable stiffness and hardening stiffness on the performance of a Vortex induced vibration (VIV) energy converter are theoretically and experimentally studied through a wake oscillator model and a computer-based force-feedback testing platform. Based on the simulation and experimental results, it is found that the bi-stable stiffness is potential to allow the system to operate at low velocity water flows, while the hardening stiffness will extend the operating range at high velocity flows. Subsequently, in order to take the advantages of both types of stiffness, a combined nonlinear stiffness is proposed and verified experimentally to demonstrate its capability in improving the overall operating range of the VIV energy converter.

Design and experiment of controlled bistable vortex induced vibration energy harvesting systems operating in chaotic regions

Abstract Vortex induced vibration based energy harvesting systems have gained interests in these recent years due to its potential as a low water current energy source. However, the effectiveness of the system is limited only at a certain water current due to the resonance principle that governs the concept. In order to extend the working range, a bistable spring to support the structure is introduced on the system. The improvement on the performance is essentially dependent on the bistable gap as one of the main parameters of the nonlinear spring. A sufficiently large bistable gap will result in a significant performance improvement. Unfortunately, a large bistable gap might also increase a chance of chaotic responses, which in turn will result in diminutive harvested power. To mitigate the problem, an appropriate control structure is required to stabilize the chaotic vibrations of a VIV energy converter with the bistable supporting structure. Based on the nature of the double-well potential energy in a bistable spring, the ideal control structure will attempt to drive the responses to inter-well periodic vibrations in order to maximize the harvested power. In this paper, the OGY control algorithm is designed and implemented to the system. The control strategy is selected since it requires only a small perturbation in a structural parameter to execute the control effort, thus, minimum power is needed to drive the control input. Facilitated by a wake oscillator model, the bistable VIV system is modelled as a 4-dimensional autonomous continuous-time dynamical system. To implement the controller strategy, the system is discretized at a period estimated from the subspace hyperplane intersecting to the chaotic trajectory, whereas the fixed points that correspond to the desired periodic orbits are estimated by the recurrence method. Simultaneously, the Jacobian and sensitivity matrices are estimated by the least square regression method. Based on the defined fixed point and the linearized model, the control gain matrix is calculated using the pole placement technique. The results show that the OGY controller is capable of stabilizing the chaotic responses by driving them to the desired inter-well period-one periodic vibrations and it is also shown that the harvested power is successfully improved. For validation purpose, a real-time experiment was carried out on a computer-based forced-feedback testing platform to validate the applicability of the controller in real-time applications. The experimental results confirm the feasibility of the controller to stabilize the responses.

Numerical investigation on VIV energy harvesting of bluff bodies with different cross sections in tandem arrangement

The VIV (Vortex Induced Vibration) energy harvesting of two bluff bodies in tandem arrangement is investigated using two-dimensional numerical simulations in the spacing range of 2–50 diameters. Five groups of bluff bodies with different cross sections (Triangular prism, Square prism, Pentagon prism, Circular cylinder and Cir-Tria prism) are analyzed. To satisfy the needs of practical application, the damping ratio of the simulation set-up is high at 0.1076. The mass ratio is low at 0.93. The simulation results indicate that the VIV response of the upstream cylinder will be suppressed when the spacing is less than 5 diameters. Due to the wake effects, the motion of the downstream cylinder is largely affected by the upstream cylinder when the spacing is less than 35 diameters. In general, the Cir-Tria prism has better performance on energy harvesting (Maximum efficiency: 26.5%). The VIV response of the square prism is lower than all other bluff bodies. The circular cylinder is much more easily influenced by the wake. No matter what the cross section is, the amplitude ratio curve of the downstream cylinder changes regularly with the spacing and could be divided into 4 areas (Blocking Area, Encouraged Area, Disturbed Area and Recovery Area).

Modeling and Experimental Validation of Vortex-Induced Vibrations (VIV) Energy Harvesting

A concept of energy harvesting from vortex-induced vibrations of a rigid circular cylinder with two piezoelectric beams attached is investigated. A mathematical model that including the coupled cylinder motion and harvested voltage is presented. The effects of the load resistance on the natural frequency and damping ratio of the vibratory system is determined by performing a linear analysis. Numerical solutions of the coupled equations for the configurations are then performed to determine the effects of varying the load resistance and wind speed,by constrasting the results on experience to investigate the harvester’s response. The results show that the system can obtain the highest harvested power at a certain velocity and load resistance.

Experimental chaotic quantification in bistable vortex induced vibration systems

The study of energy harvesting by means of vortex induced vibration systems has been initiated a few years ago and it is considered to be potential as a low water current energy source. The energy harvester is realized by exposing an elastically supported blunt structure under water flow. However, it is realized that the system will only perform at a limited operating range (water flow) that is attributed to the resonance phenomenon that occurs only at a frequency that corresponds to the fluid flow. An introduction of nonlinear elements seems to be a prominent solution to overcome the problem. Among many nonlinear elements, a bistable spring is known to be able to improve the harvested power by a vortex induced vibrations (VIV) based energy converter at the low velocity water flows. However, it is also observed that chaotic vibrations will occur at different operating ranges that will erratically diminish the harvested power and cause a difficulty in controlling the system that is due to the unpredictability in motions of the VIV structure. In order to design a bistable VIV energy converter with improved harvested power and minimum negative effect of chaotic vibrations, the bifurcation map of the system for varying governing parameters is highly on demand.In this study, chaotic vibrations of a VIV energy converter enhanced by a bistable stiffness element are quantified in a wide range of the governing parameters, i.e. damping and bistable gap. Chaotic vibrations of the bistable VIV energy converter are simulated by utilization of a wake oscillator model and quantified based on the calculation of the Lyapunov exponent. Ultimately, a series of experiments of the system in a water tunnel, facilitated by a computer-based force-feedback testing platform, is carried out to validate the existence of chaotic responses. The main challenge in dealing with experimental data is in distinguishing chaotic response from noise-contaminated periodic responses as noise will smear out the regularity of periodic responses. For this purpose, a surrogate data test is used in order to check the hypotheses for the presence of chaotic behavior. The analyses from the experimental results support the hypothesis from simulation that chaotic response is likely occur on the real system.

Experimental investigation of a drag assisted vortex-induced vibration energy converter

In this study, the Vortex-Induced Vibration (VIV) of a pivoted cylinder is experimentally investigated as a potential source of energy harvesting. The design of a physical model and a theoretical analysis presented and experimental measurements on the laboratory prototype are reported. In particular, we investigate the effect of the pivot point placement, arm length ratio (L*=l/D) and natural frequency (fN) on the VIV performance over a Reynolds number range, 2880≤Re≤22300.Classical studies show that the synchronization phenomenon (lock-in) occurs when the vortex formation frequency (fv) is close enough to the body's natural frequency (fN). Due to the configuration of the cylinder in this research, fN is also a function of flow velocity as well as the physical specifications of the system.The tests were conducted for the arm length ratio between 0.47 and 3.16 and three different spring stiffnesses were used to change the natural frequency. Results show that maximum output power is principally influenced by the arm length ration L* when the pivot point is located at the downstream, but reduced velocity is the controlling parameter when the pivot point is at the upstream. However, there is an optimum value of L* in both cases depending on the location of the pivot point and the stiffness of the spring. Based on observations, the optimum arm length ratio is relatively lower when the pivot point is at the downstream.The maximum efficiency of 31.4% has been observed for downstream placement of the pivot point by taking advantage of drag force and 2% for the upstream placement. Although the range of Reynolds numbers with high efficiency is wider when the pivot is located at the downstream, the performance of the system doesn't necessarily improve with increasing the Reynolds number in both cases.

Orientation of bluff body for designing efficient energy harvesters from vortex-induced vibrations

The characteristics and performances of four distinct vortex-induced vibrations (VIVs) piezoelectric energy harvesters are experimentally investigated and compared. The difference between these VIV energy harvesters is the installation of the cylindrical bluff body at the tip of cantilever beam with different orientations (bottom, top, horizontal, and vertical). Experiments show that the synchronization regions of the bottom, top, and horizontal configurations are almost the same at low wind speeds (around 1.5 m/s). The vertical configuration has the highest wind speed for synchronization (around 3.5 m/s) with the largest harvested power, which is explained by its highest natural frequency and the smallest coupled damping. The results lead to the conclusion that to design efficient VIV energy harvesters, the bluff body should be aligned with the beam for low wind speeds (<2 m/s) and perpendicular to the beam at high wind speeds (>2 m/s).

Application of Vortex Induced Vibration Energy Generation Technologies to the Offshore Oil and Gas Platform: The Preliminary Study

Application of Vortex Induced Vibration Energy Generation Technologies to the Offshore Oil and Gas Platform: The Preliminary Study

Modeling and Optimization of a Vortex Induced Vibration Fluid Kinetic Energy Harvester

In this contribution a fluid kinetic energy harvester excited by vortex induced vibration (VIV) is proposed. In terms of describing and verifying the interaction between the structural and the fluidic domain, a two-way Fluid Structure Interaction (FSI) simulation has been carried out. In order to optimize the harvester, different designs have been investigated to improve the performance. Subsequently, a demonstrator setup for testing the manufactured harvester has been assembled. The experimental results were compared with that of FSI-simulations. By applying the optimized harvester structure, the vortex induced pressure could be enhanced 4 times compared to convetional structures. The results show that the VIV energy harvester deliver 1μW power output under 2 m/s air flows.

Attachment of Tripping Wires to Enhance the Efficiency of a Vortex-Induced Vibrations Energy Generation System

Attachment of Tripping Wires to Enhance the Efficiency of a Vortex-Induced Vibrations Energy Generation System