{"title":"Making Effective WEC Design Choices Based on Simulation and Analysis","authors":"C. Vance, J. Ringsberg, Shun-Han Yang","doi":"10.1115/OMAE2019-95138","DOIUrl":"https://doi.org/10.1115/OMAE2019-95138","url":null,"abstract":"\u0000 The study presents analyses of key parameters that affect the performance of the point absorbing wave energy converter (WEC). Performance is assessed by running hydrodynamic and structural response simulations and calculating the power absorption of the WEC and fatigue damage in the mooring lines from the output data. The baseline model of the WEC input to the simulation is modelled after the WaveEL 3.0 device, designed by Waves4Power and installed in Runde, Norway. Simulations are run for single buoy and small array configurations, varying environmental conditions, mooring system, and WEC buoy shaft length. Environmental conditions are chosen to reflect locations studied as potential future installation sites. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on water depth, and that optimal shaft length depends on the average sea conditions at the location. The array simulations show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the four-buoy array configuration is the most profitable, and both the LCOE and LCA show that the main process contribution to climate change and the total product cost is the manufacturing of the WEC buoy itself. The research in this study demonstrates the importance of using simulations to make effective WEC design choices for a given environment.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123637928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Aeromechanical Analysis of Wind Turbines Using Non-Linear Harmonic Method","authors":"S. W. Naung, M. Rahmati, H. Farokhi","doi":"10.1115/omae2019-96256","DOIUrl":"https://doi.org/10.1115/omae2019-96256","url":null,"abstract":"\u0000 In this paper, aeromechanical analysis of wind turbines is presented. The distinctive feature of this paper is the use of frequency based non-linear harmonic method which is an efficient computational method to study unsteady periodic flow and aeroleasticity of turbomachinery applications, and extensive validation of the non-linear harmonic method against conventional time domain solution methods. This paper is an extension of the authors’ previous work which analysed the aerodynamics of the MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine. Aeromechanical analysis of the MEXICO-Experiment wind turbine as well as 1.5 MW wind turbine are conducted in this study. Both conventional time domain solution method and non-linear harmonic method are used, and compared to each other for validation and verification of the non-liner harmonic method. Using the same numerical set-up for each method demonstrates the differences and capabilities of each solution method, and their computational expenses. Finally, this paper concludes with how the aeromechanical analysis of large wind turbines can be performed effectively and efficiently using the non-linear harmonic method.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129082884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Experimental Study on Coupled Motions of a Spar-Buoy Under Mathieu Instability","authors":"T. Iseki, Peng Xu","doi":"10.1115/omae2019-95937","DOIUrl":"https://doi.org/10.1115/omae2019-95937","url":null,"abstract":"\u0000 A series of experiments were carried out to investigate the occurrence of the Mathieu-type instability. The main objective of this study is utilization of an auto-parametrically excited oscillation for wave energy converters. In this paper, the subject is the auto-parametrically excited oscillation of a spar-buoy type point absorber with two degrees of freedom. A small spar buoy model with a ballast controlling system was made and the model experiments were conducted to realize the large oscillating motion based on the Mathieu-type instability. The ballast controlling system is installed in the buoy model and the vertical movement of the ballast produces a certain change of the pitching natural period. Using the controlling system, the pitching motion in regular waves under the heave resonant period was measured. In some experiments, it was observed that the large pitching motion occurred suddenly, and the time histories showed different excitation pattern from the theoretical Mathieu-type instability. Based on the model experiments and considerations of the theory of Mathieu-type instability, the occurrence of the large pitching motion is discussed.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"244 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133848886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Dynamic Response of Spar-Type Floating Offshore Wind Turbine in Freak Wave","authors":"You-gang Tang, Yan Li, Xie Peng, X. Qu, Wang Bin","doi":"10.1115/omae2019-95638","DOIUrl":"https://doi.org/10.1115/omae2019-95638","url":null,"abstract":"\u0000 Simulations are conducted in time domain to investigate the dynamic response of a SPAR-type floating offshore wind turbine under the scenarios with freak wave. Towards this end, a coupled aero-hydro numerical model is developed. The methodology includes a blade-element-momentum model for aerodynamics, a nonlinear model for hydrodynamics, a nonlinear restoring model of SPAR buoy, and a nonlinear algorithm for mooring cables. The OC3 Hywind SPAR-type FOWT is chosen as an example to study the dynamic response under the freak conditions, while the time series of freak wave is generated by the Random Frequency Components Selection Phase Modulation Method. The motions of platform, the tensions in the mooring lines and the power generation performance are documented in different cases. According to the simulations, it shows that the power coefficient of wind turbine decreased rapidly at the moment when freak wave acted on the floating structure.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124064694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. E. Sheshtawy, O. E. Moctar, T. Schellin, S. Natarajan
{"title":"Numerical Investigation of an Optimised Horizontal Axis Tidal Stream Turbine","authors":"H. E. Sheshtawy, O. E. Moctar, T. Schellin, S. Natarajan","doi":"10.1115/omae2019-95722","DOIUrl":"https://doi.org/10.1115/omae2019-95722","url":null,"abstract":"\u0000 A tidal stream turbine was designed using one of the optimised hydrofoils, whose lift-to-drag ratio at an angle of attack of 5.2 degrees was 4.5% higher than that of the reference hydrofoil. The incompressible Reynolds-averaged Navier Stokes equations in steady state were solved using k-ω (SST) turbulence model for the reference and optimised tidal stream turbines. The discretisation errors and the effect of different y+ values on the solution were analysed. Thrust and power coefficients of the modelled reference turbine were validated against experimental measurements. Output power and thrust of the reference and the optimised tidal turbines were compared. For a tip speed ratio of 3.0, the output power of the optimised tidal turbine was 8.27% higher than that of the reference turbine of the same thrust.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127838909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shengtao Zhou, Chao Li, Yiqing Xiao, F. Lemmer, Wei Yu, P. Cheng
{"title":"Effects of Platform Mounting Orientations on the Long-Term Performance of a Semisubmersible Wind Turbine","authors":"Shengtao Zhou, Chao Li, Yiqing Xiao, F. Lemmer, Wei Yu, P. Cheng","doi":"10.1115/omae2019-96240","DOIUrl":"https://doi.org/10.1115/omae2019-96240","url":null,"abstract":"\u0000 Due to the non-fully-symmetrical configuration, the platform laying angle of semi-submersible floating offshore wind turbines relative to wind/wave load directions has a noticeable influence on the dynamics characteristics of the whole structure, which indicates that the platform mounting orientation should be carefully considered before installation at sea. The directionality effects of short-term wind/wave loads had been discussed in previous studies, which are, however, insufficient to make a full understanding of the directionality impacts. In our study, based on a 25-year met-ocean database, long-term analysis is carried out by means of an efficient frequency-domain model with eight degrees of freedom. The nonlinear quantities such as aerodynamic loads, aerodynamic damping and mooring stiffness are derived from the time-domain simulation tool FAST, serving as a preprocessing database for the frequency-domain model. A case study is carried out by comparing the long-term responses of a Y-shape semi-submersible floating wind turbine in four mounting orientations. Significant differences can be seen. The platform mounted in the most unfavorable orientation tends to suffer from larger peak nacelle acceleration, which would increase the loads and cause higher tower base fatigue damage. These findings highlight the importance of platform mounting orientations and can serve as a basis for the installation of semi-submersible floating wind turbines.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130900557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Performance of a Passive Tuned Liquid Column Damper for Floating Wind Turbines","authors":"Wei Yu, F. Lemmer, P. Cheng","doi":"10.1115/omae2019-96360","DOIUrl":"https://doi.org/10.1115/omae2019-96360","url":null,"abstract":"\u0000 The motivation of the present paper is to show the proof-of-concept of a passive Tuned Liquid Column Damper (TLCD) for floating wind turbines, which increases the platform pitch damping and power production under wind and wave excitations. As the first step, a reliable TLCD model is implemented and coupled with a reduced order floating wind turbine model. Here, the TLCD is modelled as a second order system which is known for ships, whereas the structural model is a coupled aero-hydro-servo-elastic model with five degrees of freedom. The results show that the TLCD is able to damp the platform resonances but to a limited extent, which is inline the findings of previous research. However, the improved platform pitch stability allows a larger blade pitch control bandwidth, which is normally limited by the underdamped soft support platform. Therefore, by introducing the passive TLCD into the floating wind turbine system, a better power production is achieved.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114712024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Geometrical Optimization of U-Oscillating Water Columns in Random Waves","authors":"A. Scialò, G. Malara, F. Arena","doi":"10.1115/omae2019-95973","DOIUrl":"https://doi.org/10.1115/omae2019-95973","url":null,"abstract":"\u0000 This paper deals with the problem of designing an optimal U - Oscillating Water Column (U-OWC) device equipped with a Wells turbine. Specifically, the paper proposes the implementation of a genetic algorithm for designing a U-OWC exposed to the typical sea states available in the Mediterranean Sea. The first challenge encountered in this problem is the efficient calculation of the U-OWC hydrodynamic parameters. The second challenge relates to the fact that the U-OWC dynamics is governed by two coupled nonlinear ordinary differential equations with no closed-form solution. For reducing the computational cost, the genetic algorithm is combined with a semi-analytical approach used for determining the U-OWC hydrodynamic parameters and with a statistical linearization based approximate solution of the equations governing the U-OWC dynamics. Such a procedure allows estimating efficiently, albeit approximately, the power output of the system.\u0000 Numerical results compare a design based on a conventional “design sea state” vis-à-vis a design based on a “design wave climate”. For this purpose, the case study of the Roccella Jonica marina (Reggio Calabria, Italy) is considered, as relevant wave data are available to characterize the most energetic seas as well as depicting the global wave climate available at that location. The numerical results highlight the fact that an optimization conducted on the basis of a design sea state does not lead to an optimal design in a wave climate.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127000250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daniel de Oliveira Costa, Joel Sena Sales Junior, A. C. Fernandes
{"title":"Oscillating Water Column Motion Inside Circular Cylindrical Structures","authors":"Daniel de Oliveira Costa, Joel Sena Sales Junior, A. C. Fernandes","doi":"10.1115/omae2019-96048","DOIUrl":"https://doi.org/10.1115/omae2019-96048","url":null,"abstract":"\u0000 A non-linear mathematical model is presented for the Equation of Motion of the Water Column inside circular cylindrical structures in different cases, comparing to previous models in literature. Experimental model tests were carried out investigating the water column decay under given initial conditions, and an analysis is performed for each cycle showing the dynamic behaviour of OWC evolving in time. The results show asymmetric pattern in the time series acquired in the decay tests as a consequence of variations of the Added Length and quadratic viscous damping as the direction of the flow changes, as observed in previous studies.\u0000 A general procedure is proposed to assess the unknown parameters including the quadratic damping viscous coefficients through the concept of “equivalent linear harmonic” as a linearisation of such terms, enlightening its dependence on the motion amplitude as well as the water column draft.\u0000 Experimental data for the OWC response under a set of incoming regular waves is also presented, comparing the results to numerical simulation through a solver based on the estimation of the damping coefficients obtained in the decay tests.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":" 67","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132187703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Impact of Simulation Duration for Offshore Floating Wind Turbine Analysis Using a Coupled FAST-OrcaFlex Model","authors":"A. Pillai, P. Thies, L. Johanning","doi":"10.1115/OMAE2019-95159","DOIUrl":"https://doi.org/10.1115/OMAE2019-95159","url":null,"abstract":"\u0000 This paper uses a coupled FAST-OrcaFlex model in order to explore the impact of simulation duration on model convergence. The work analyses both operational and extreme cases, assessing the estimated fatigue and extreme loads experienced by a floating offshore wind turbine and its mooring system. Considering an OC4 semi-submersible deployed with the NREL 5 MW turbine, the case study performs a parametric sweep over a range of wind speeds, sea states, and simulation durations. Through this sweep, the paper establishes the impact of the simulation duration for this particular floating offshore wind turbine and characterizes the convergence properties of the loads and excursions as a function of the simulation duration. The results inform the selection of simulation durations to be used in coupled aero-hydro models and optimization frameworks for floating offshore wind applications and can be used to aid the development of guidance and standards for coupled floating offshore wind turbine models.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132952302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}