• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.566-570
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• 2016

본 연구에서는 플라잉 디스크를 이용하여 Pitching 운동 조건에서의 공력특성을 해석하였다. 본 해석에서 사용한 플라잉 디스크 모델은 프리원 151_140이며, 해석자로는 KFLOW_EDISON_2D_3DOF를 사용하였다. Pitching 운동이 있는 경우 받음각의 변화에 따른 공력특성을 비교 분석하였다. 기준 받음각의 변화에 따라 형상 아랫면과 뒷전 부근에 실속 와류가 다른 형태로 생겨 플라잉 디스크의 공력 특성에 영향을 준다는 것을 확인하였다. 또한, 기준 받음각이 증가 할수록 강한 실속 와류가 발생함을 알 수 있다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.9-18
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• 2016

The slender structures such as high rise building or marine riser are highly susceptible to dynamic force exerted by fluid-structure interactions among which vortex-induced vibration(VIV) is the main cause of dynamic unstability of the structural system. If VIV occurs in natural frequency regime of the structure, fatigue failure likely happens by so-called lock-in phenomenon. This study presents the numerical analysis of dynamic behavior of both structure and fluid in the lock-in regimes and investigates the subjacent phenomena to hold the resonance frequency in spite of the change of flow condition. Unsteady and laminar flow was considered for a two-dimensional circular cylinder which was assumed to move freely in 1 degree of freedom in the direction orthogonal to the uniform inflow. Fluid-structure interaction was implemented by solving both unsteady flow and dynamic motion of the structure sequentially in each time step where the fluid domain was remeshed considering the movement of the body. The results show reasonable agreements with previous studies and reveal characteristic features of the lock-in phenomena. Not only the lift force but also drag force are drastically increasing during the lock-in regime, the vertical displacement of the cylinder reaches up to 20% of the diameter of the cylinder. The correlation analysis between lift and vertical displacement clearly show the dramatic change of the phase difference from in-phase to out-of-phase when the cylinder experiences lock-in. From the results, it can be postulated that the change of phase difference and flow condition is responsible for the resonating behavior of the structure during lock-in.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.686-687
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.292-293
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• 2013

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.168-177
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• 2024

When designing an underwater Piezoelectric Energy Harvester (PEH), Vortex Induced Vibration (VIV) is generated throughout the cantilever through a change in curvature, and the generation of VIV increases the vibration displacement of the curved cantilever PEH, which is an important factor in increasing actual power. The material of the curved PEH selected a Polyvinyline Di-Floride (PVDF) piezoelectric film, and the flow velocity is set at 0.1 m/s to 0.50 m/s for 50 mm, 130 mm, and 210 mm with various curvatures. The strain energy change of PEH by VIV was observed. The smaller the radius of curvature, the larger the VIV, and as the flow rate increased, more VIV appeared. Rapid shape transformation due to the small curvature was effective in generating VIV, and strain energy, normalized voltage, average power, etc. To increase the amount of power of the PEH, it is considered that the average power will increase as the number of curved PEHs increases as well as the steep curvature is improved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.170-175
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• 2005

The focus of this paper is to observe the aerodynamic and vibration characteristics of the NACA0012 blade(AR=16.6) fixed on the lower surface of the wind tunnel, by changing air speed and the blade's angle of attack. After fixing a slit-typed vortex generator on the front of the blade, it could be observed that the vibrational characteristics caused by interactions between vortex and blade through the 5-hole pilot tubes. And, also, two different blades in stiffness had been prepared for observing those characteristics above in this experiment. The results were compared with the given stiffness of blade, as well. According to the results, it is clear to recognize that the vibration spectrum increases while air speed and angle of attack increase, and, also, less stiffness means bigger vibration spectrum.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.449-453
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• 2007

After over a century of effort by researchers and engineers, the problem of bluff body flow, in particular vortex shedding frequency, remains almost entirely in the empirical, descriptive realm of knowledge. Computational methods have been systematically applied for vortex-induced vibrations of the cable-stayed bridge with steel composite deck by unsteady wind loadings due to vortex-shedding. The focus of this paper is to predict the vortex-induced vibration of the cable-stayed bridge with steel composite deck based computational fluid dynamics(CFD).

• Journal of Ocean Engineering and Technology
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• v.31 no.5
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• pp.364-370
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• 2017

A numerical model based on the mode superposition method is used to study the vortex-induced vibration response characteristics of a deep-sea riser such as steel catenary riser (SCR). A steel catenary riser can be modeled using a flexible cable with simple supports at both ends. The natural frequency, mode shape and mode curvature of the riser are calculated and the vortex-induced vibration response of the riser is obtained using the equilibrium of the input and output power. The mode superposition method is applied to the vibrational stresses for each mode to calculate the overall riser fatigue life.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.147-150
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• 2002

For lightweight and flexible structures, it is important to suppress the vibrations induced by interactions between fluid and structures. This paper presents the PPF/Adaptive control of the vortex-induced vibration of composite beam with rigid cylinder in which the fluid force is considered as an external excitation on the structure. For the problems considered here, the excitation frequency (vortex-shedding frequency) is assumed to be equal to the natural frequency of the structure. A pair of piezoceramic devices attached bottom of the composite structure was used as actuators. Simulation and experiment were carried out with the designed controller and effectiveness of the PPF/Adaptive PPF control was verified by both experimental and simulation results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.166-171
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• 2013

In this study, low noise designs of a Savonius wind turbines are numerically investigated. From a previous study, it was found that the high harmonic components whose fundamental frequency is higher than the BPF were found to be dominant in noise spectrum of a Savonius wind turbine. On a basis of this observation, S-shaped blade tip is proposed as a low design factors that decrease wind turbine noise by inducing phase differences in vortex shedding. The conventional Savonius and S-shaped turbines are investigated using Hybrid CAA method where flow field around the turbine are computed using CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow data. Noise reductions by these design factors are confirmed by comparing the predicted noise levels from these turbines.