A Study on Non-Linear Response of Moored Floating Body Considering Dynamic Motion of Mooring Lines

2013 ◽  
Author(s):  
Keiji Nonaka ◽  
Motohiko Murai ◽  
Atsushi Nagamine
Keyword(s):  
Wind Turbine ◽  
Linear Response ◽  
Floating Body ◽  
Shallow Sea ◽  
Offshore Structure ◽  
Mooring Lines ◽  
Dynamic Motion ◽  
Sea Bottom ◽  
Floating Type ◽  
Sea Area

Recently, the utilization of the ocean space has attracted researcher’s attention which encouraged by the development of resources in seafloor and the offshore structure such as wind turbine. Offshore structure is essential for the utilization of the ocean space. In the case that we install an offshore structure in the shallow sea area, we use simpler structure such as the TLP (Tension Leg Platform) which can reach the sea bottom. However, in recent years the demand for offshore structure in deeper sea area has increased, thus we frequently use more flexible floating type offshore structure with strand chain mooring.

Study on the Dynamic Response for Floating Foundation of Offshore Wind Turbine

2011 ◽  
Author(s):  
Yougang Tang ◽  
Jun Hu ◽  
Liqin Liu
Keyword(s):  
Wind Turbine ◽  
Wind Farm ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Load ◽  
Mooring Lines ◽  
Floating Foundation ◽  
Wind Turbine System ◽  
Sea Area

The wind resources for ocean power generation are mostly distributed in sea areas with the distance of 5–50km from coastline, whose water depth are generally over 20m. To improve ocean power output and economic benefit of offshore wind farm, it is necessary to choose floating foundation for offshore wind turbine. According to the basic data of a 600kW wind turbine with a horizontal shaft, the tower, semi-submersible foundation and mooring system are designed in the 60-meter-deep sea area. Precise finite element models of the floating wind turbine system are established, including mooring lines, floating foundation, tower and wind turbine. Dynamic responses for the floating foundation of offshore wind turbine are investigated under wave load in frequency domain.

Comparison of Dynamic Response in a 2MW Floating Offshore Wind Turbine During Typhoon Approaches

2019 ◽  
Author(s):  
Koji Tanaka ◽  
Iku Sato ◽  
Tomoaki Utsunomiya ◽  
Hiromu Kakuya
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Atmospheric Pressure ◽  
Offshore Wind ◽  
Floating Body ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Maximum Wave Height ◽  
Sea Area ◽  
Good Agreement

Abstract In this paper, we describe the analysis of the dynamic response of a 2 MW floating offshore wind turbine (FOWT) at the time of typhoon attack in the actual sea area. In order to introduce floating offshore wind turbine in Asia, it is essential to evaluate the influence of typhoon attack accurately. This FOWT, named HAENKAZE is the only FOWT to operate commercially in areas where typhoons occur. On July 3rd, 2018, the strongest typhoon (Prapiroon) at the installed area of the FOWT since its installation approached the HAENKAZE. The central atmospheric pressure of the typhoon at the closest time was 965 hPa, the maximum instantaneous wind speed at the hub height was 52.2 m/s, and the maximum wave height was 7.1 m. In this paper, the dynamic response of the floating body at the time of typhoon attack is compared for the measured and the simulated values. As a result of the comparison, basically a good agreement has been obtained between the measured and the simulated values except for yaw response, for which the simulated values considerably overestimate the measured values.

Coupled Dynamic Analysis for Multi-Unit Floating Offshore Wind Turbine in Maximum Operational and Survival Conditions

2015 ◽  
Author(s):  
H. K. Jang ◽  
H. C. Kim ◽  
M. H. Kim ◽  
K. H. Kim
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Random Waves ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines

Numerical tools for a single floating offshore wind turbine (FOWT) have been developed by a number of researchers, while the investigation of multi-unit floating offshore wind turbines (MUFOWT) has rarely been performed. Recently, a numerical simulator was developed by TAMU to analyze the coupled dynamics of MUFOWT including multi-rotor-floater-mooring coupled effects. In the present study, the behavior of MUFOWT in time domain is described through the comparison of two load cases in maximum operational and survival conditions. A semi-submersible floater with four 2MW wind turbines, moored by eight mooring lines is selected as an example. The combination of irregular random waves, steady currents and dynamic turbulent winds are applied as environmental loads. As a result, the global motion and kinetic responses of the system are assessed in time domain. Kane’s dynamic theory is employed to formulate the global coupled dynamic equation of the whole system. The coupling terms are carefully considered to address the interactions among multiple turbines. This newly developed tool will be helpful in the future to evaluate the performance of MUFOWT under diverse environmental scenarios. In the present study, the aerodynamic interactions among multiple turbines including wake/array effect are not considered due to the complexity and uncertainty.

Effects of Disturbance of Current Field on Power Characteristics of a Floating Type Pitch-Controlled VAMT in a Real Sea

2016 ◽  
Author(s):  
Tomoki Ikoma ◽  
Koichi Masuda ◽  
Hiroaki Eto ◽  
Chang-Kyu Rheem ◽  
Osamu Enomoto
Keyword(s):  
Fluid Velocity ◽  
Vertical Axis ◽  
Ocean Waves ◽  
Floating Body ◽  
Maximum Output ◽  
Power Characteristics ◽  
Turbine Performance ◽  
Velocity Changes ◽  
Floating Type ◽  
Japanese Islands

While a type of marine turbine for tidal current generation can be chosen from several types, a vertical axis marine turbine (VAMT) should be better in Japan because sea areas around Japanese islands where current velocity is sufficient are limited. This study conducted a sea test of a VAMT of a floating type installed with six straight pitch-controllable blades. The cycloidal mechanism was adapted for the pitch control. The purpose of the study is to understand effects of ocean waves and motion of a floating body on turbine performance and behaviours of the VAMT in unideal current conditions. Besides, the data taken should be effective to consider that effects in order to design VAMTs. The setup with the setting angle of −30 degrees suggested highest performance from the sea tests, then 15% in maximum turbine power and maximum output was 40W. Ocean waves strongly affected on the turbine performance because fluid velocity changes due to ocean waves and it was unable to neglect the variation of the velocity in spite of small. The characteristics of the turbine sensitively varied because of ocean waves. The results suggested that during accelerating and decelerating incoming fluid speed, characteristics of the turbine were different in each case.

Effect of Foundation Modeling of a Jack-Up Crane Vessel on the Dynamic Motion Response of an Offshore Wind Turbine Blade During Installation

2018 ◽  
Author(s):  
Yuna Zhao ◽  
Zhengshun Cheng ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Soil Structure ◽  
Offshore Wind ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Dynamic Motion ◽  
Motion Responses ◽  
Jack Up ◽  
Offshore Crane

Nowadays, there is an increasing demand for use of jack-up crane vessels to install offshore wind turbines. These vessels usually have shallow soil penetration during offshore crane operations because of the requirement of frequent repositioning. The soil-structure interaction should thus be properly modeled for evaluating the motion responses, especially at crane tip at large lifting height. Excessive crane tip motion affects the dynamic responses of the lifted components and subsequently affects the safety and efficiency of operations. The present study addresses the effects of soil behaviour modeling of a typical jack-up crane vessel on the dynamic motion responses of a wind turbine blade during installation using a fully coupled method. The coupled method account for wind loads on the blade and the vessel hull, wave loads on the vessel legs, soil-structure interaction, structural flexibility of the vessel legs and crane, and the mechanical wire couplings. Three models for the soil-leg interactions and two soil types are considered. The foundation modeling is found to have vital effects on the system dynamic motion responses. The characteristics of system motion differ under different types of soil. Compared to the combined linear spring and damper model, the simplified pinned and fixed foundations respectively lead to significant overestimation and underestimation of the motion responses of the blade during installation by jack-up crane vessels. To ensure safe and efficient offshore operations, detailed site specific soil properties should be used in numerical studies of offshore crane operations using jack-up crane vessels.

scholarly journals Dynamic Response of Floating Wind Turbine Under Consideration of Dynamic Behavior of Catenary Mooring-Lines

2017 ◽  
Author(s):  
Shuangxi Guo ◽  
Yilun Li ◽  
Min Li ◽  
Weimin Chen ◽  
Yiqin Fu
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Nonlinear Dynamic ◽  
Ocean Waves ◽  
Wave Frequency ◽  
Mooring Line ◽  
Mooring Lines ◽  
Restoring Force ◽  
Dynamic Behaviors ◽  
Floating Wind Turbine

Recently, wind turbine has been developed from onshore area to offshore area because of more powerful available wind energy in ocean area and more distant and less harmful noise coming from turbine. As it is approaching toward deeper water depth, the dynamic response of the large floating wind turbine experiencing various environmental loads becomes more challenge. For examples, as the structural size gets larger, the dynamic interaction between the flexible bodies such as blades, tower and catenary mooring-lines become more profound, and the dynamic behaviors such as structural inertia and hydrodynamic force of the mooring-line get more obvious. In this paper, the dynamic response of a 5MW floating wind turbine undergoing different ocean waves is examined by our FEM approach in which the dynamic behaviors of the catenary mooring-line are involved and the integrated system including flexible multi-bodies such as blades, tower, spar platform and catenaries can be considered. Firstly, the nonlinear dynamic model of the integrated wind turbine is developed. Different from the traditional static restoring force, the dynamic restoring force is analyzed based on our 3d curved flexible beam approach where the structural curvature changes with its spatial position and the time in terms of vector equations. And, the modified finite element simulation is used to model a flexible and moving catenary of which the hydrodynamic load depending on the mooring-line’s motion is considered. Then, the nonlinear dynamic governing equations is numerically solved by using Newmark-Beta method. Based on our numerical simulations, the influences of the dynamic behaviors of the catenary mooring-line on its restoring performance are presented. The dynamic responses of the floating wind turbine, e.g. the displacement of the spar and top tower and the dynamic tension of the catenary, undergoing various ocean waves, are examined. The dynamic coupling between different spar motions, i.e. surge and pitch, are discussed too. Our numerical results show: the dynamic behaviors of mooring-line may significantly increase the top tension, particularly, the peak-trough tension gap of snap tension may be more than 9 times larger than the quasi-static result. When the wave frequency is much higher than the system, the dynamic effects of the mooring system will accelerate the decay of transient items of the dynamic response; when the wave frequency and the system frequency are close to each other, the displacement of the spar significantly reduces by around 26%. Under regular wave condition, the coupling between the surge and pitch motions are not obvious; but under extreme condition, pitch motion may get about 20% smaller than that without consideration of the coupling between the surge and pitch motions.

Effects of the Mooring Line Configuration on the Dynamics of a Point Absorber

2013 ◽  
Author(s):  
Vincenzo Nava ◽  
Marin Rajic ◽  
Carlos Guedes Soares
Keyword(s):  
Case Studies ◽  
Time Instant ◽  
Floating Body ◽  
Mooring Line ◽  
Mooring Lines ◽  
Point Absorber ◽  
Line Configuration ◽  
Frequency Domains ◽  
Restoring Forces ◽  
Static Approach

The aim of this paper is to study the dynamics of a floating body with characteristics comparable to a point absorber wave energy converter with different mooring systems, in geometrical configuration or in the materials. To this purpose, the dynamics of a moored buoy is investigated. The point absorber is modeled as a spherical buoy in plane two-dimensional motion, and it is studied under the action of irregular unidirectional wind-generated waves, moored to the seabed by means of one, two or three mooring lines. Two different sets of moorings are considered, and typical wires and chains used in offshore technology are considered, leading to a total of 6 case studies. A quasi-static approach is used for modeling the restoring forces needed to keep buoy into station, using an innovative iterative procedure able to predict for each time instant and for each cable the lay down length of the cable, being each mooring line allowed to be taut or slack. Approaches in the time and frequency domains are used to obtain the system responses in intermediate waters, where these facilities are usually installed. Results for all case studies are compared both in terms of statistics of response and tensions on the top of the cable.

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