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Collaborating Authors
Facilities Design, Construction and Operation
Dynamic Analysis of Fixed Bottom Offshore Wind Turbines
Throumoulopoulosv, Amfilochios G. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Loukogeorgakiv, Eva (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Dimitriou, Aristarchos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh))
ABSTRACT In this paper, a numerical tool (MicroSAS-OWT) for the integrated analysis of Offshore Wind Turbines (OWTs) with fixed-bottom support structure of arbitrary shape is presented. MicroSAS-OWT is developed through the coupling of FAST with MicroSAS. FAST is used for modeling the rotor nacelle assembly, while the tower and the support structure are modeled in MicroSAS. The interface of the two codes is ensured at the tower top. The tool is applied for the case of the NREL 5MW OWT that consists of a monopile support structure with rigid foundation, and is preliminary assessed through comparison of results with the corresponding ones obtained using FAST. Stress analysis of the tower and the support structure is also performed. INTRODUCTION Offshore wind energy represents a very promising kind of renewable energy source. Offshore Wind Turbines (OWTs) are considered nowadays as an attractive alternative solution to the onshore ones offering multiple benefits and addressing effectively the well-known obstacles and problems associated with the latter ones (Henderson et al., 2003; Breton and Moe, 2009; Esteban et al., 2011). The efficient exploitation of offshore wind energy necessitates the successful handling of several challenges related to developmental, economical and technological issues (Musial et al., 2006). Among these challenges, one of the most crucial is the development, investigation, assessment and adoption of new design concepts, especially for the support structure. These new design concepts will allow the placement of OWTs in deeper water and therefore, the operation of larger capacity OWTs. Considering the high complexity characterizing any OWT system, resulting from its inherent characteristics (e.g. variability and intense interaction of components) and from its operation in a complex environment, where different loading sources exist, the development/application of suitable numerical tools is critical for addressing efficiently the previously mentioned challenge.
- North America > United States (1.00)
- Europe (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (1.00)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.92)
A Numerical Tool For the Integrated Analysis of Fixed-Bottom Offshore Wind Turbines
Loukogeorgaki, Eva (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Llorente, Carlos (McDermott Inc.)
ABSTRACT In this paper, a numerical tool (MicroSAS-OWT) for the integrated analysis of Offshore Wind Turbines (OWTs) with fixed-bottom support structure of arbitrary shape is presented. MicroSAS-OWT is developed through the coupling of FAST with MicroSAS. FAST is used for modeling the rotor nacelle assembly, while the tower and the support structure are modeled in MicroSAS. The interface of the two codes is ensured at the tower top. The tool is applied for the case of the NREL 5MW OWT that consists of a monopile support structure with rigid foundation, and is preliminary assessed through comparison of results with the corresponding ones obtained using FAST. Stress analysis of the tower and the support structure is also performed. INTRODUCTION Offshore wind energy represents a very promising kind of renewable energy source. Offshore Wind Turbines (OWTs) are considered nowadays as an attractive alternative solution to the onshore ones offering multiple benefits and addressing effectively the well-known obstacles and problems associated with the latter ones (Henderson et al., 2003; Breton and Moe, 2009; Esteban et al., 2011). The efficient exploitation of offshore wind energy necessitates the successful handling of several challenges related to developmental, economical and technological issues (Musial et al., 2006). Among these challenges, one of the most crucial is the development, investigation, assessment and adoption of new design concepts, especially for the support structure. These new design concepts will allow the placement of OWTs in deeper water and therefore, the operation of larger capacity OWTs. Considering the high complexity characterizing any OWT system, resulting from its inherent characteristics (e.g. variability and intense interaction of components) and from its operation in a complex environment, where different loading sources exist, the development/application of suitable numerical tools is critical for addressing efficiently the previously mentioned challenge.
- North America > United States (1.00)
- Europe (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (1.00)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.91)
Investigation of the Accuracy of "Time Snapshot" Based Structural Analysis And Design of Jacket Type Platforms
Farmakis, George E. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh))
ABSTRACT The focus of this article is the evaluation of the traditional method of time domain analysis regarding its assumption that the maximum stresses of the structural members appear at the same time and specifically, at the time of the base shear maximization. Two procedures are followed for the analysis of identical offshore jacket type models in order to gain adequate data for performing comparisons between them. The first, is the generally used method mentioned above, while the second examines every member independently during time domain simulation and reveals the maximum values of their internal forces and moments whenever they appear. Various comparisons between the two groups of results are performed, and the final conclusions are presented. INTRODUCTION The society's needs for energy often leads to the construction of offshore structures; traditionally for oil exploration and production, and for most recently for wind energy exploitation. According to EWEA (European Wind Energy Association, 2012), 235 new Offshore Wind Turbines in nine wind farms were fully grid connected in the year 2011. Offshore structures are subjected to the wave load, which is dynamic and thus, a need for dynamic analysis arise for their safe design. For the dynamic analysis two main approaches are used, frequency domain analysis and time domain analysis. In the case of Offshore Wind Turbines, a time domain approach is preferable primarily due to the nature of the wind load. Several investigators have dealt with time domain simulation. Kurian et al. (2010) worked on the dynamic behavior of semi submergible platforms. Pollio et al. (2006) investigated the non linear dynamic behavior of risers in the time domain, using an implementation of the Runge-Kutta algorithm. Morooka et al. (2006) demonstrated that time domain can address better riser nonlinearities, while frequency domain analysis makes easier the handling of the solution obtained and requires less computational efforts, in general.
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Risers (0.68)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (0.54)
ABSTRACT: The risk of failing to achieve the acceptable performance (performance risk) of a free floating structure under the combined action of various wave frequencies is investigated in the frequency domain. Here, performance is quantified in terms of no exceedance of a threshold for the response level corresponding to each degree of freedom. Quantification of the performance risk is based on a Monte Carlo simulation technique. The numerical analysis of the free floating structure is carried out using a three dimensional hydrodynamic analysis. Several cases of different combinations of wave frequencies are investigated. The second-order hydrodynamic interactions of pertinent wave frequencies are considered in the analysis for each combination examined. Two issues are investigated, namely:performance and performance risk for the free floating structure considered. The performance and risk levels of the second-order solution are compared with the results of the corresponding first-order solution in order to investigate the significance of second-order quantities in the assessment of both performance and performance risk levels. According to the results generated by the present study, secondorder wave effects can generally strongly affect performance and performance risk levels. INTRODUCTION Considering the case of a free floating body subjected to the simultaneous action of two or more wave frequencies, non-linear hydrodynamic analysis needs to be carried since second-order wave effects can highly affect the response of the free floating body. This happens because several effects can hardly be predicted when using linear (first-order) theory, such as wave drifting and interaction between wave trains of different frequencies (Murao, 1960; Newman, 1990 and 2004 and McIver, 1992). For this reason, plenty of investigations, relevant to the analysis and computation of second-order wave effects have been carried out including among others Kosmeyer et al. (1988), Lee (1991) and Kim M.H. (1992 and 1993).
- Europe (1.00)
- North America > United States (0.28)
- Asia > Japan (0.28)
- Management > Risk Management and Decision-Making (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (0.88)
Fatigue Analysis of a Tripod Supporting Structure of an Offshore Wind Turbine
Zacharioudaki-Apelidou, Fotini (Department of Civil Engineering, Aristotle University of Thessaloniki) | Dedonakis, Fotios (Department of Civil Engineering, Aristotle University of Thessaloniki) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki)
ABSTRACT Offshore Wind Turbines (OWT) are exposed to loads varying both in time and in amplitude, designating fatigue damage as a main concern. In this paper, an analysis is presented for assessing the total fatigue damage of an OWT tripod supporting structure. The combined effect of wind and wave loading is computed and different loading scenarios are examined to determine the dominating load on the final result. Further investigation is done to assess the influence of different welding profiles of the tubular joints of the structure on the final fatigue resistance. Results are presented and conclusions are drawn, indicating the importance of the combined analysis. INTRODUCTION The geography of Greece consists of numerous inhabited smaller and bigger islands, with energy needs varying throughout the year. This decentralized demand for energy can be addressed by providing the islands with an autonomous source of energy production. Offshore Wind Turbines (OWT) are an appealing alternative to satisfy this need. A solution like this would allow the islands to use their own resources and produce their own energy in an environmentally friendly way. The realization of OWT is a complicated task and an engineering challenge. Several design scenarios have to be taken into account, including extreme load and fatigue load cases. OWT are exposed to critical environmental loads, which designate this kind of analysis essential. Contrary to common offshore structures- such as oil and gas platforms, OWT are not only exposed to dynamic wave loads but also to dynamic loads from the turning rotor of the Wind Turbine. These loads make OWT susceptible to fatigue damage. Loads varying in amplitude, direction and time act on the structure throughout its lifetime, progressively reducing the fatigue resistance. Deeper water depths for installation and turbines of larger size used nowadays, lead to increased loadings upon the supporting structure.
- Europe (1.00)
- North America > United States (0.69)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (0.92)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.82)
- Health, Safety, Environment & Sustainability > Environment (0.67)