Wave and Wind Responses of a Very-Light FOWT with Guy-Wired-Supported Tower: Numerical and Experimental Studies

Abstract

A floating offshore wind turbine (FOWT) concept with a guy-wire-supported tower was investigated to obtain motion results in waves considering its elastic model characteristics. The FOWT concept studied aims to reduce the construction costs by using a light-weight structure tensioned with guy wires and a downwind type. Wave tank experiments of an elastically similar segmented backbone model in the 1:60 scale were carried out to clarify the dynamic elastic response features of the structure. The experimental results were compared with numerical simulations obtained from NK-UTWind and WAMIT codes. The bending moment measured at the tower and pontoons had two peak values for different wave periods carried out. The short-wave period peak was due to sagging/hogging when the wavelength matched the floater length. The second peak was due to the large tower top acceleration, which caused a large bending moment at the tower base and pontoon to support the inertia force. The wind force was not significant to modify the FOWT response. The sensibility analysis in pontoons and tower rigidities confirmed the importance of the guy wires to support the inertia due to the waves and wind incidence. The new concept of a very-light FOWT with a guy-wire-supported tower may be an option for future FOWT developments.

Dynamic Behavior of a Flexible Multi-Column FOWT in Regular Waves

“…First, the full-scale FOWT was numerically modeled and analyzed using a coupled analysis code for the rotor-floater-mooring response. The code used was the NK-UTWind (an in-house code developed by UTokyo for coupled analysis of FOWT, see [18]); other articles that present details about the use of NK-UTWind can be found, for example, in [10,13,20].…”

“…Thus, the rigidity effects on the dynamic behavior in waves are essential. The variance of the heave motion in these wave conditions was estimated from the 0th moment m 0 of the heave response spectrum as: m 0 = S 33 (f)df (10) The significant response of heave is evaluated as 4 √ m 0 . The results of significant wave height were 24.2 and 13.4 mm for the EI 0 and 5EI 0 models.…”

“…Various floater types of FOWT have been researched to meet the demand for wind energy production in the seas. In Japan, where FOWT is estimated to have a substantial potential for power generation, several types of research have been undertaken at the initiative of the New Energy and Industrial Technology Development Organization (NEDO); such as a barge type at Kitakyushu [3][4][5][6], semi-submersibles [7][8][9][10], and spar types at Fukushima [11,12].…”

“…In this case, the elastic deformation of the elements will be profound and need to be discussed concerning structural stability and durability. As an example of a new concept for flexible floaters, a research of a guy-wired supported-tower FOWT can be found in [10,13], suggesting FOWT with guy wires can be the right candidate for further cost reduction.…”

Seakeeping Tests of a FOWT in Wind and Waves: An Analysis of Dynamic Coupling Effects and Their Impact on the Predictions of Pitch Motion Response

“…The Jappaku floater dynamics in waves was numerically evaluated in the frequency domain by the radiation-diffraction code WAMIT ® [25]. Hull geometry and mass/inertia matrix were pre-computed using Edtools ® through parametric structure modeling [26]. In the numerical mesh, hull columns were represented by high-order surfaces with panel size 5, while the heave plates were modeled using dipole panels (zero-thickness).…”