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와류기인진동을 이용한 신재생에너지 발전에서 유체력 추정연구
박홍래 한국신·재생에너지학회 2023 신재생에너지 Vol.19 No.2
Vortex-induced vibrations are a type of flow-induced vibrations caused by alternating lift forces. With increasing demandfor renewable energy, the application of vortex-induced vibrations to renewable energy has been widely studied. Vortex-inducedvibrations for aquatic clean energy (VIVACE) converter is a renewable energy device that generates electricity from rivers or oceansusing vortex-induced vibrations. To increase the design life and power harnessing capacity of the VIVACE converter, the estimationof fluid forces due to vortex-induced vibrations is essential. Herein, vortex-induced vibrations were experimentally tested, and theiramplitude and frequency response were measured. The amplitude results showed four different branches: initial branch, upper branch,lower branch, and desynchronization range. According to the fluid force coefficient results, the maximum lift coefficient occurred atthe upper branch. Additionally, a mathematical model is proposed to estimate fluid forces due to vortex-induced vibrations withoutusing measurement devices. This mathematical model enables the estimation of fluid force coefficients and phase lag using amplitudeand frequency response of vortex-induced vibrations.
최현규,홍석윤,송지훈,장원석,최원석 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-
Recently, the evaluation of vortex-induced vibration has emerged as a significantly important issue owing to the development of high-speed and lightweight ships and submarines. To derive an accurate vortex-induced vibration response, it is essential to consider the fluid-structure interaction. Moreover, it is necessary to evaluate the generation of the fluid-structure interaction to effectively prevent catastrophic failure in the structures. In this study, a hydrofoil wake oscillator model was developed based on a near-vortex strength that considers the fluid-structure interaction. The near-vortex strength was calculated from the boundary layer on a trailing edge to overcome the empirical parameter of lift fluctuation in conventional wake oscillator models. To predict the vortex-induced vibration on a hydrofoil, procedures for calculating the near-vortex strength and coupling the structural equations and fluid equation were introduced. The vortex-induced vibration derived using the developed hydrofoil wake oscillator model was verified by comparison it against the experimental results. The results reveal that the derived amplitude and lock-in range of the vortex-induced vibration were consistent with the experimental results. In addition, the extent of occurrence of the fluid-structure interaction and its contribution to vortex-induced vibration were evaluated using a non-dimensional wake parameter.
Numerical investigation of vortex shedding and vortex-induced vibration for flexible riser models
전정수,김우전 대한조선학회 2010 International Journal of Naval Architecture and Oc Vol.2 No.2
The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.
Numerical investigation of vortex shedding and vortex-induced vibration for flexible riser models
Chen, Zheng-Shou,Kim, Wu-Joan The Society of Naval Architects of Korea 2010 International Journal of Naval Architecture and Oc Vol.2 No.2
The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.
높은 레이놀즈수에서 와류에 의해 진동하는 원통에 대한 수치해석적 연구
김상덕,김현수 한국지식정보기술학회 2024 한국지식정보기술학회 논문지 Vol.19 No.1
Vortex shedding from a bluff body in the flow field yields an external force acting on the object. This causes an elastic body to vibrate (VIV, vortex induced vibration) and also affects the evolution of vortices. This interaction between vibrating structures and vortices is being studied in various industrial fields in relation to structural fatigue. VIV is influenced by various system variables such as fluid-to-structure mass ratio, structural stiffness, damping, and surface roughness. Experimental studies were conducted on various structural stiffnesses and damping for a cylinder oscillating perpendicular to the flow in a channel. In many cases, investigations have been conducted on laminar flow with low Reynolds numbers or cases lower than the critical Reynolds number. Turbulence characteristics are not dominant and the shear layer has strong two-dimensional characteristics in such regimes. Previous researches for high Reynolds number, however, are limited. Current investigation was conducted on a circular cylinder moving induced by vortices at various high Reynolds numbers through numerical analyses. In predicting the maximum amplitude of the cylinder vibration, the results of this study showed a good comparison with the experiment at low Reynolds number in the initial branch, but showed some differences from the experiment in the condition where synchronization of vortex shedding and cylinder vibration occurs in lock-in regime. In the ratio of the vibrating frequency and the natural frequency of the cylinder, the prediction of the transition from the initial branch to the upper branch and from the upper branch to the lower branch showed good comparison with the experiment.
Wind-induced vibration control of a 200 m-high tower-supported steel stack
Susuki, Tatsuya,Hanada, Naoya,Homma, Shin,Maeda, Junji Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.5
It is well known that cylinder steel stacks are heavily impacted by vortex-induced vibration. However, the wind-induced vibration behaviors of tower-supported steel stacks are not clarified due to a lack of observation. We studied a stack's response to strong winds over a long period of time by observing the extreme wind-induced vibration of a 200 m-high tower-supported steel stack. This experiment aimed to identify the wind-induced vibration properties of a tower-supported steel stack and assess the validity of the vibration control method used in the experiment. Results revealed a trend in wind-induced vibration behavior. In turn, an effective measure for controlling such vibration was defined by means of increasing the structural damping ratio due to the effects of the tuned mass damper to dramatically decrease the vortex-induced vibration of the stack.
Study on the mechanism of the vortex-induced vibration of a bluff double-side box section
Yu Li,Chen Li,Feng Wang,Jia-Wu Li 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.2
At present, researchers mainly focused on the vortex-induced vibration (VIV) of the double-side I-shaped girder, while there are only a few literatures focused on the VIV of the bluff double-side box girder, especially the study on the synchronous pressure- and vibration- measured test for the bluff double-side box girder has not been reported. Therefore, in this study, the vibration-measured test, the Numerical Wind Tunnel Simulation, and the synchronous pressure- and vibration- measured test were conducted to study the VIV mechanism of the bluff double-side box girder. Firstly, a section model of the bluff double-side box girder was designed, and the vibration-measured test was conducted to study the influence of mass ratio, damping ratio, and aerodynamic countermeasures on the VIV of the bluff double-side box girder. Secondly, the Numerical Wind Tunnel Simulation was conducted to simulate the vorticity evolution of the bluff double-side box girder, which was used to help analyze the results of the synchronous pressure- and vibration- measured test. Finally, the synchronous pressure- and vibration- measured test was conducted to investigate the wind pressure distribution and aerodynamic forces on the surface of the double-side box girder, which was then used to study the VIV mechanism of the bluff double-side box girder by combining the simulated vorticity evolutions. So, when the VIV of the double-side box girder occurs, it is found that: there is a significant difference in the mean and fluctuating wind pressure between the upper and lower surfaces; moreover, at the leading and trailing edges, the aerodynamic forces contribute greatly to the VIV, the correlation between the aerodynamic forces and the vortex-induced aerodynamic forces is positive, and with the increase of this coefficient, it will lead to the more significant VIV.
황재승 한국풍공학회 2021 한국풍공학회지 Vol.25 No.4
부공력감쇠는 풍직각방향의 와류공진을 예측하는데 있어서 매우 중요한 요소이다. 부공력감쇠는 진동유발하중 또는 피드백 하중을 구성하는 주요인자로 와류진동이 급격히 발현되는 현상을 설명하는 도구이기도 하다. 본 연구에서는 공력감쇠의 수학적 모델 을 제시하고 와류유발하중모델과 함께 와류진동을 예측하는 프러세스를 제안한다. 직사각형단면에 대한 공기력진동실험을 수행하여, 계측된 가속도로부터 공력감쇠와 와류유발하중을 추정하고 이에 기반하여 공력감쇠모델과 와류유발하중모델을 구축하는 과정을 다룬 다. 최종적으로 공력감쇠모델과 와류유발하중 모델에 대한 재해석을 통하여 가속도응답을 구하고 계측된 가속도와 비교하여 모델의 진동예측성능을 평가한다. 본 연구에서 제안된 와류하중모델의 진동예측성능을 평가한 결과 안정적이며, 신뢰도가 높은 와류진동예측 이 가능함을 알 수 있었다. The negative aerodynamic damping is a very crucial parameter in estimating the vortex induced resonance(VIR) in the across-wind direction. Aerodynamic damping is a major factor constituting so-called motion induced load or feedback load, and it is also a tool to explain the rapid manifestation of VIR. In this study, a mathematical model of aerodynamic damping are evaluated, and a process for predicting vortex induced vibration(VIV) along with vortex induced load model is proposed. By performing aeroelastic model test of a slender structure with a rectangular section, the aerodynamic damping and vortex-induced load are identified from the measured acceleration, based on these results, the mathematical models for aerodynamic damping and vortex induced load with respect to the wind speed were constructed. Finally, vibration estimation performance was evaluated by comparing the measured acceleration with the acceleration response obtained through re-analysis using the aerodynamic damping model and the vortex induced load model. From the numerical results, it was found that mathematical model of across wind load model are able to reliably predict VIV with a high reliability.
Yanguo Sun,Mingshui Li,Haili Liao 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.17 No.6
Obvious vortex induced vibration (VIV) was observed during section model wind tunnel tests for a single main cable suspension bridge. An optimized section configuration was found for mitigating excessive amplitude of vibration which is much larger than the one prescribed by Chinese code. In order to verify the maximum amplitude of VIV for optimized girder, a full bridge aeroelastic model wind tunnel test was carried out. The differences between section and full aeroelastic model testing results were discussed. The maximum amplitude derived from section model tests was first interpreted into prototype with a linear VIV approach by considering partial or imperfect correlation of vortex-induced aerodynamic force along span based on Scanlan’s semi-empirical linear model. A good consistency between section model and full bridge model was found only by considering the correlation of vortex-induced force along span.
Sun, Yanguo,Li, Mingshui,Liao, Haili Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.6
Obvious vortex induced vibration (VIV) was observed during section model wind tunnel tests for a single main cable suspension bridge. An optimized section configuration was found for mitigating excessive amplitude of vibration which is much larger than the one prescribed by Chinese code. In order to verify the maximum amplitude of VIV for optimized girder, a full bridge aeroelastic model wind tunnel test was carried out. The differences between section and full aeroelastic model testing results were discussed. The maximum amplitude derived from section model tests was first interpreted into prototype with a linear VIV approach by considering partial or imperfect correlation of vortex-induced aerodynamic force along span based on Scanlan's semi-empirical linear model. A good consistency between section model and full bridge model was found only by considering the correlation of vortex-induced force along span.