The Experts below are selected from a list of 414 Experts worldwide ranked by ideXlab platform

Jens Peter Kofoed - One of the best experts on this subject based on the ideXlab platform.

  • Validation of a Tool for the Initial Dynamic Design of Mooring Systems for Large Floating Wave Energy Converters
    Journal of Marine Science and Engineering, 2017
    Co-Authors: Jonas Bjerg Thomsen, Francesco Ferri, Jens Peter Kofoed
    Abstract:

    Mooring of floating wave energy converters is an important topic in renewable research since it highly influences the overall cost of the wave energy converter and thereby the cost of energy. In addition, several wave energy converter failures have been observed due to insufficient Mooring systems. When designing these systems, it is necessary to ensure the applicability of the design tool and to establish an understanding of the error between model and prototype. The present paper presents the outcome of an experimental test campaign and construction of a numerical model using the open-source boundary element method code NEMOH and the commercial time-domain Mooring Analysis tool OrcaFlex. The work used the wind/wave energy converter Floating Power Plant as a case study, which is defined as a large floating structure with a passive Mooring system. The investigated Mooring consists of a three-legged turret system with synthetic lines, and it was tested for both operational and extreme events. In order to understand the difference between the model and experimental results, no tuning of the model was done, besides adding drag elements with values found from a simplified methodology. This resembles initial design cases where no experimental data are available. Generally good agreement was found for the tensions in the lines when the drag element was applied, with some overestimation of the motions. The main cause of difference was found to be underestimation of linear damping. A model was tested with additional linear damping, and it illustrated that a final Analysis needs to use experimental data to achieve the best results. However, the analyses showed that the investigated model can be used without tuning in initial investigations of Mooring systems, and it is expected that this approach can be applied to other similar systems.

  • screening of available tools for dynamic Mooring Analysis of wave energy converters
    Energies, 2017
    Co-Authors: Jonas Bjerg Thomsen, Francesco Ferri, Jens Peter Kofoed
    Abstract:

    The focus on alternative energy sources has increased significantly throughout the last few decades, leading to a considerable development in the wave energy sector. In spite of this, the sector cannot yet be considered commercialized, and many challenges still exist, in which Mooring of floating wave energy converters is included. Different methods for assessment and design of Mooring systems have been described by now, covering simple quasi-static Analysis and more advanced and sophisticated dynamic Analysis. Design standards for Mooring systems already exist, and new ones are being developed specifically forwave energy converter Moorings, which results in other requirements to the chosen tools, since these often have been aimed at other offshore sectors. The present Analysis assesses a number of relevant commercial software packages for full dynamic Mooring Analysis in order to highlight the advantages and drawbacks. The focus of the assessment is to ensure that the software packages are capable of fulfilling the requirements of modeling, as defined in design standards and thereby ensuring that the Analysis can be used to get a certified Mooring system. Based on the initial assessment, the two software packages DeepC and OrcaFlex are found to best suit the requirements. They are therefore used in a case study in order to evaluate motion and Mooring load response, and the results are compared in order to provide guidelines for which software package to choose. In the present study, the OrcaFlex code was found to satisfy all requirements.

Jonas Bjerg Thomsen - One of the best experts on this subject based on the ideXlab platform.

  • Validation of a Tool for the Initial Dynamic Design of Mooring Systems for Large Floating Wave Energy Converters
    Journal of Marine Science and Engineering, 2017
    Co-Authors: Jonas Bjerg Thomsen, Francesco Ferri, Jens Peter Kofoed
    Abstract:

    Mooring of floating wave energy converters is an important topic in renewable research since it highly influences the overall cost of the wave energy converter and thereby the cost of energy. In addition, several wave energy converter failures have been observed due to insufficient Mooring systems. When designing these systems, it is necessary to ensure the applicability of the design tool and to establish an understanding of the error between model and prototype. The present paper presents the outcome of an experimental test campaign and construction of a numerical model using the open-source boundary element method code NEMOH and the commercial time-domain Mooring Analysis tool OrcaFlex. The work used the wind/wave energy converter Floating Power Plant as a case study, which is defined as a large floating structure with a passive Mooring system. The investigated Mooring consists of a three-legged turret system with synthetic lines, and it was tested for both operational and extreme events. In order to understand the difference between the model and experimental results, no tuning of the model was done, besides adding drag elements with values found from a simplified methodology. This resembles initial design cases where no experimental data are available. Generally good agreement was found for the tensions in the lines when the drag element was applied, with some overestimation of the motions. The main cause of difference was found to be underestimation of linear damping. A model was tested with additional linear damping, and it illustrated that a final Analysis needs to use experimental data to achieve the best results. However, the analyses showed that the investigated model can be used without tuning in initial investigations of Mooring systems, and it is expected that this approach can be applied to other similar systems.

  • screening of available tools for dynamic Mooring Analysis of wave energy converters
    Energies, 2017
    Co-Authors: Jonas Bjerg Thomsen, Francesco Ferri, Jens Peter Kofoed
    Abstract:

    The focus on alternative energy sources has increased significantly throughout the last few decades, leading to a considerable development in the wave energy sector. In spite of this, the sector cannot yet be considered commercialized, and many challenges still exist, in which Mooring of floating wave energy converters is included. Different methods for assessment and design of Mooring systems have been described by now, covering simple quasi-static Analysis and more advanced and sophisticated dynamic Analysis. Design standards for Mooring systems already exist, and new ones are being developed specifically forwave energy converter Moorings, which results in other requirements to the chosen tools, since these often have been aimed at other offshore sectors. The present Analysis assesses a number of relevant commercial software packages for full dynamic Mooring Analysis in order to highlight the advantages and drawbacks. The focus of the assessment is to ensure that the software packages are capable of fulfilling the requirements of modeling, as defined in design standards and thereby ensuring that the Analysis can be used to get a certified Mooring system. Based on the initial assessment, the two software packages DeepC and OrcaFlex are found to best suit the requirements. They are therefore used in a case study in order to evaluate motion and Mooring load response, and the results are compared in order to provide guidelines for which software package to choose. In the present study, the OrcaFlex code was found to satisfy all requirements.

Kostas F Lambrakos - One of the best experts on this subject based on the ideXlab platform.

  • model test data correlations with fully coupled hull Mooring Analysis for a floating wind turbine on a semi submersible platform
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Andrew J Goupee, Kostas F Lambrakos
    Abstract:

    The DeepCwind floating wind turbine model tests were performed at MARIN (Maritime Research Institute Netherlands) with a model set-up corresponding to a 1:50 Froude scaling. In the model tests, the wind turbine was a scaled model of the National Renewable Energy Lab (NREL) 5MW, horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semi-submersible and a tension-leg platform (TLP) (Ref. [1] and [2]). This paper presents validation of the MLTSIM-FAST [3] code with DeepCwind semi-submersible wind turbine model test results. In this integrated program, the turbine tower and rotor dynamics are simulated by the subroutines of FAST [4], and the hydrodynamic loads and Mooring system dynamics are simulated by the subroutines of MLTSIM. In this study, fully coupled hull/Mooring dynamics and second-order difference-frequency response are included in MLTSIM-FAST. The Analysis results are systematically compared with model test results and show good agreement.Copyright © 2014 by ASME

  • Model Test Data Correlations With Fully Coupled Hull/Mooring Analysis for a Floating Wind Turbine on a Semi-Submersible Platform
    Volume 9B: Ocean Renewable Energy, 2014
    Co-Authors: Andrew J Goupee, Kostas F Lambrakos
    Abstract:

    The DeepCwind floating wind turbine model tests were performed at MARIN (Maritime Research Institute Netherlands) with a model set-up corresponding to a 1:50 Froude scaling. In the model tests, the wind turbine was a scaled model of the National Renewable Energy Lab (NREL) 5MW, horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semi-submersible and a tension-leg platform (TLP) (Ref. [1] and [2]). This paper presents validation of the MLTSIM-FAST [3] code with DeepCwind semi-submersible wind turbine model test results. In this integrated program, the turbine tower and rotor dynamics are simulated by the subroutines of FAST [4], and the hydrodynamic loads and Mooring system dynamics are simulated by the subroutines of MLTSIM. In this study, fully coupled hull/Mooring dynamics and second-order difference-frequency response are included in MLTSIM-FAST. The Analysis results are systematically compared with model test results and show good agreement.Copyright © 2014 by ASME

Don Spencer - One of the best experts on this subject based on the ideXlab platform.

  • numerical vortex induced vibration prediction of marine risers in time domain based on a forcing algorithm
    Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2014
    Co-Authors: Don Spencer
    Abstract:

    Vortex-induced vibration (VIV) of marine risers poses a significant challenge as the offshore oil and gas industry moves into deep water. A time-domain Analysis tool has been developed to predict the VIV of marine risers based on a forcing algorithm and by making full use of the available high Reynolds number experimental data. In the formulation, the hydrodynamic damping is not treated as a special case but simply an extension of the experimentally derived lift curves. The forcing algorithm was integrated into a Mooring Analysis program based on the global coordinate-based finite element method. At each time step, the added mass, lifting force, and drag force coefficients and their corresponding loads are computed for each element. Validation studies have been carried out for a full-scale rigid riser segment and a model-scale flexible riser. The numerical results were compared with experimental data and solutions by other programs.

  • time domain viv prediction of marine risers
    ASME 2012 31st International Conference on Ocean Offshore and Arctic Engineering, 2012
    Co-Authors: Don Spencer
    Abstract:

    Vortex Induced Vibration (VIV) of marine risers poses a significant challenge as the offshore oil and gas industry moves into deep water. A time-domain Analysis tool has been developed to predict the VIV of marine risers based on a forcing algorithm and by making full use of the available high Reynolds number experimental data. In the formulation, the hydrodynamic damping is not treated as a special case but simply an extension of the experimentally derived lift curves. The forcing algorithm was integrated into a Mooring Analysis program based on the global-coordinate based finite element method. At each time step, the added mass, lifting force and drag force coefficients and their corresponding loads are computed for each element. Validation studies have been carried out for a full-scale rigid riser segment and a model-scale flexible riser. The numerical results were compared with experimental data and solutions by other programs.Copyright © 2012 by ASME

Francesco Ferri - One of the best experts on this subject based on the ideXlab platform.

  • Validation of a Tool for the Initial Dynamic Design of Mooring Systems for Large Floating Wave Energy Converters
    Journal of Marine Science and Engineering, 2017
    Co-Authors: Jonas Bjerg Thomsen, Francesco Ferri, Jens Peter Kofoed
    Abstract:

    Mooring of floating wave energy converters is an important topic in renewable research since it highly influences the overall cost of the wave energy converter and thereby the cost of energy. In addition, several wave energy converter failures have been observed due to insufficient Mooring systems. When designing these systems, it is necessary to ensure the applicability of the design tool and to establish an understanding of the error between model and prototype. The present paper presents the outcome of an experimental test campaign and construction of a numerical model using the open-source boundary element method code NEMOH and the commercial time-domain Mooring Analysis tool OrcaFlex. The work used the wind/wave energy converter Floating Power Plant as a case study, which is defined as a large floating structure with a passive Mooring system. The investigated Mooring consists of a three-legged turret system with synthetic lines, and it was tested for both operational and extreme events. In order to understand the difference between the model and experimental results, no tuning of the model was done, besides adding drag elements with values found from a simplified methodology. This resembles initial design cases where no experimental data are available. Generally good agreement was found for the tensions in the lines when the drag element was applied, with some overestimation of the motions. The main cause of difference was found to be underestimation of linear damping. A model was tested with additional linear damping, and it illustrated that a final Analysis needs to use experimental data to achieve the best results. However, the analyses showed that the investigated model can be used without tuning in initial investigations of Mooring systems, and it is expected that this approach can be applied to other similar systems.

  • screening of available tools for dynamic Mooring Analysis of wave energy converters
    Energies, 2017
    Co-Authors: Jonas Bjerg Thomsen, Francesco Ferri, Jens Peter Kofoed
    Abstract:

    The focus on alternative energy sources has increased significantly throughout the last few decades, leading to a considerable development in the wave energy sector. In spite of this, the sector cannot yet be considered commercialized, and many challenges still exist, in which Mooring of floating wave energy converters is included. Different methods for assessment and design of Mooring systems have been described by now, covering simple quasi-static Analysis and more advanced and sophisticated dynamic Analysis. Design standards for Mooring systems already exist, and new ones are being developed specifically forwave energy converter Moorings, which results in other requirements to the chosen tools, since these often have been aimed at other offshore sectors. The present Analysis assesses a number of relevant commercial software packages for full dynamic Mooring Analysis in order to highlight the advantages and drawbacks. The focus of the assessment is to ensure that the software packages are capable of fulfilling the requirements of modeling, as defined in design standards and thereby ensuring that the Analysis can be used to get a certified Mooring system. Based on the initial assessment, the two software packages DeepC and OrcaFlex are found to best suit the requirements. They are therefore used in a case study in order to evaluate motion and Mooring load response, and the results are compared in order to provide guidelines for which software package to choose. In the present study, the OrcaFlex code was found to satisfy all requirements.