Low-Height Lifting System for Offshore Wind Turbine Installation: Modelling and Hydrodynamic Response Analysis Using the Commercial Simulation Tool Sima

2021 ◽  
Author(s):  
Thiago Gabriel Monteiro ◽  
David V\xe5gnes ◽  
Karl Henning Halse ◽  
Hans Petter Hildre
2021 ◽  
Author(s):  
Jiafeng Xu ◽  
Behfar Ataei ◽  
Karl Henning Halse ◽  
Hans Petter Hildre ◽  
Egil Tennfjord Mikalsen

Author(s):  
Lin Li ◽  
Zhen Gao ◽  
Torgeir Moan

This study addresses numerical modeling and time-domain simulations of the lowering operation for installation of an offshore wind turbine monopile (MP) with a diameter of 5.7 m and examines the nonstationary dynamic responses of the lifting system in irregular waves. Due to the time-varying properties of the system and the resulting nonstationary dynamic responses, numerical simulation of the entire lowering process is challenging to model. For slender structures, strip theory is usually applied to calculate the excitation forces based on Morison's formula with changing draft. However, this method neglects the potential damping of the structure and may overestimate the responses even in relatively long waves. Correct damping is particularly important for the resonance motions of the lifting system. On the other hand, although the traditional panel method takes care of the diffraction and radiation, it is based on steady-state condition and is not valid in the nonstationary situation, as in this case in which the monopile is lowered continuously. Therefore, this paper has two objectives. The first objective is to examine the importance of the diffraction and radiation of the monopile in the current lifting model. The second objective is to develop a new approach to address this behavior more accurately. Based on the strip theory and Morison's formula, the proposed method accounts for the radiation damping of the structure during the lowering process in the time-domain. Comparative studies between different methods are presented, and the differences in response using two types of installation vessel in the numerical model are also investigated.


Author(s):  
David Vågnes ◽  
Thiago Gabriel Monteiro ◽  
Karl Henning Halse ◽  
Hans Petter Hildre

Abstract With the increasing demand for renewable energy sources in the past years, the interest in expanding the use of wind energy has grown. The next frontier in this expansion process is the use of floating wind turbines offshore. One of the main factors dictating the economic feasibility of such wind turbines is the complexity of their installation process. The dimensions of modern offshore wind turbines, the distance from the installation sites to the coast and demanding environmental factors all contribute to the difficult of developing an efficient installation concept for this kind of structures. In this work, we present a new concept for a catamaran vessel capable of handling the deployment of offshore wind turbines on floating spar platforms using a low-height lifting system that connects to the lower end of the wind turbine. The low-height lifting system is controlled by an active heave compensation system and constant tension tugger wires attached to the turbine mid-section are used to ensure the balance of the tower during the installation process. We conducted a series of hydrodynamic analysis using the software suit SIMA to study the dynamic response of the proposed system under different weather conditions and different operational layouts. This preliminary concept was proven feasible from a hydrodynamic point of view and can now be pushed forward for further studies regarding other aspects of the operation, such as impact and structural loads and mechanical design of components.


Author(s):  
Zhu Ming ◽  
Zhang Peng ◽  
Zhu Changming

In this paper, a dynamic model for the offshore wind turbine installation is proposed. And this model is coupled by the wind turbine and the floating crane considering 6-DOF floating crane, 5-DOF wind turbine and elastic stretch of the hoisting cable. And when the wind turbine lands on the supporting structure, the displacement constraint is applied at the wind turbine. During the process, the relaxation of the hoisting cable is considered. In addition, the nonlinear hydrostatic force, environmental force, hoisting cable force and mooring force are considered as the external force. The motions of wind turbine and the floating crane are studied. From the numerical analysis, it is found that the release velocity, the release height and wave condition have a great effect on the motion of wind turbine.


Author(s):  
Baptiste Elie ◽  
Guillaume Oger ◽  
David Le Touzé

Abstract The present study addresses the first steps of development and validation of a coupled CFD-BE (Blade Element) simulation tool dedicated to offshore wind turbine farm modelling. The CFD part is performed using a weakly-compressible solver (WCCH). The turbine is taken into account using FAST (from NREL) and its effects are imposed into the fluid domain through an actuator line model. The first part of this paper is dedicated to the presentation of the WCCH solver and its coupling with the aero-elastic modules from FAST. In a second part, for validation purposes, comparisons between FAST and the WCCH-FAST coupling are presented and discussed. Finally, a discussion on the performances, advantages and limitations of the formulation proposed is provided.


Author(s):  
Daewoong Son ◽  
Pauline Louazel ◽  
Bingbin Yu

Abstract Wind forces acting on an offshore wind turbine are transferred to the bottom of the tower and consequently to the floating structure. Thus, drag forces acting on each component of the wind turbine such as the blades, the nacelle, and the tower must be accounted for properly in order to evaluate the performance of the supporting platform. In the aero-elastic wind turbine simulation tool FAST v.7, the nacelle drag component, however, has not been implemented, which means that only the drag forces on the tower and on the blades are represented. In this work, the front and side nacelle drag forces are modelled in FAST v.7 via different drag contributions. This paper will examine the behavior of a floating offshore semisubmersible platform, the WindFloat, for different Rotor-Nacelle-Assembly (RNA) yaw-misalignments with emphasis on the nacelle drag component.


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