Motions of a 5 MW floating VAWT evaluated by numerical simulations and model tests

2017 ◽  
Vol 144 ◽  
pp. 21-34 ◽  
Author(s):  
Liqin Liu ◽  
Ying Guo ◽  
Haixiang Zhao ◽  
Yougang Tang
Author(s):  
Mathieu Brotons ◽  
Philippe Jean

The accurate prediction of SPM vessel yaw motion is important to its mooring system design. Inconsistencies have been observed between the numerical and model test predictions of offloading responses. In some cases, the numerical simulation predicted unstable yaw behavior of the vessel (fishtailing) while the model tests did not show such instability. This discrepancy between experiment and theory casts doubt as to whether the numerical simulation predicts correctly the vessel yaw motion. The work presented in this paper investigates the following two hypotheses to possibly explain the non-expected fishtailing in the numerical simulations: The mooring software may not accurately integrate non-linear differential equations that describe the yaw motion of the SPM vessel. Some damping terms may be under-estimated in the software (user input issue). To validate the integration scheme of the system of non-linear differential equations as implemented in the mooring software, a stability analysis has been conducted on a shuttle tanker moored to a West Africa deep water buoy. Variations of parameters like the hawser length, its axial stiffness and the vessel’s drag coefficients have been studied to explore their impacts on the vessel yaw stability. The approach is to identify without performing any time domain simulations, the domains of stability by linearizing the differential equations of SPM vessel’s yaw motion around its equilibrium point. The validity of the developed approach is then confirmed by performing time domain simulations of the same case. The second conjecture which may explain the non-expected fishtailing in numerical simulations was that some damping terms may be under-estimated. A semi empirical formula for the drag moment can be derived from rotation tests and comparisons were performed with the engineering model implemented in the mooring analysis software. The results show that by calibrating this damping term with the one derived from the experiments, the numerical simulations would match the stable yaw motion behavior as predicted during model tests. Following the above findings, a tool has been developed to fit the yaw drag moment engineering model based on experimental measurements, for any case of mooring analysis.


2016 ◽  
Vol 11 (3) ◽  
pp. 679-692 ◽  
Author(s):  
Hossain Md. Shahin ◽  
Teruo Nakai ◽  
Kenji Ishii ◽  
Toshikazu Iwata ◽  
Shou Kuroi

2020 ◽  
Vol 22 (3) ◽  
pp. 594-610
Author(s):  
Xianglian Xu ◽  
Mingxin Bai ◽  
Hongxing Yang ◽  
Meng Xiong ◽  
Wenqiang Zhu ◽  
...  

1986 ◽  
Vol 1 (20) ◽  
pp. 198
Author(s):  
K.C. Tang ◽  
M.T. Tsai ◽  
Y.R. Hwang ◽  
H.H. Hwung

In general, hydraulic model tests and numerical simulations can be used for securing enough informations in order to assess the environmental impact by thermal discharge after the power plant operation. However, the numerical simulations should be verified by the consequence of hydraulic model tests or the field data. Then, the numerical model can be used as a prediction model to foresee the nature of thermal diffusion when the additional generators will be operated. The third nuclear power plant in Taiwan has been constructed in 1984. In order to protect the abundant corals which distributed on the rocky bottom around this power plant, a complete studies on thermal diffusion have been performed, accordingly, a verification with field measurements were also made in this paper.


2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Massimina Castiglia ◽  
Tony Fierro ◽  
Filippo Santucci de Magistris

The design and the manufacture of the oil and gas pipelines are being improved over the years in response to the observed damages and related disastrous effects. The improvements are possible, thanks to the increasing knowledge about pipeline performances in specific contexts. The seismic hazard on buried pipelines has always been of major concern, and the earthquake-induced soil liquefaction effects are among the most important issues to be accounted for in the design. Experiences based on case histories, experimental modelling, and numerical simulations represent the source of understanding of the involved mechanisms, the affecting parameters, and the structure response. Recently, all these aspects are becoming more accurate, thanks to the use of monitoring systems. The protection of pipelines from the seismic hazard is a crucial and challenging issue. This paper provides an overview of the research that has been conducted over the years in the specific framework of soil liquefaction phenomenon. Case histories on pipeline performances, commonly adopted analytical methods, and results of model tests and numerical simulations are summarized with main focus on the level of knowledge achieved up to date and the existing limitations that represent open issues for further development of the research. This study represents a useful background to be adopted from academics and practitioners in order to enhance the methods of analyses of the pipelines, thus improving their performances in the applications of the oil and gas industry.


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