• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.693-700
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• 2003

An evaluation method for flutter derivatives is proposed, using indicial functions of structural members produced by Computational Fluid Dynamics (CFD). Flutter derivatives are obtained by Fourier integration of indicial functions. Instead of direct simulation of oscillating objects, only the calculation of time-dependent lift and moment variations of fixed objects with constant attack angle are necessary.The Finite Element Method (FEM) is developed as a tool for the numerical method. For two rectangular sections having different aspect ratios, the numerical analysis and wind tunnel test are carried out to inspect the adequacy of this study. The results proved to be good, and they could be used for a preliminary design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.5
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• pp.368-375
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• 2018

In the present study, aerodynamic load analysis for a floating off-shore wind turbine was conducted to examine the effect of periodic platform motion in the direction of 6-DOF on rotor aerodynamic performance. Blade-element momentum method(BEM) was used for a numerical simulation, the unsteady airload effects due to the flow separation and the shed wake were considered by adopting a dynamic stall model based on the indicial response method. Rotor induced downwash was estimated using the momentum theory, coupled with empirical corrections for the turbulent wake states. The periodic platform motions including the translational motion in the heave, sway and surge directions and the rotational motion in the roll, pitch and yaw directions were considered, and each platform motion was applied as a sinusoidal function. For the numerical simulation, NREL 5MW reference wind turbine was used as the target wind turbine. The results showed that among the translation modes, the surge motion has the largest influence on changing the rotor airloads, while the effect of pitch motion is predominant for the rotations.