The Experts below are selected from a list of 21 Experts worldwide ranked by ideXlab platform

Y Drobyshevski - One of the best experts on this subject based on the ideXlab platform.

  • integrated analysis of mooring and riser systems for fpso s in harsh shallow water environments
    ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering, 2011
    Co-Authors: M Martens, J R Whelan, Y Drobyshevski
    Abstract:

    Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) Conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean Conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO Condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the Metocean Conditions, an offset envelope for each governing Metocean Condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated Metocean Conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.Copyright © 2011 by ASME

  • Integrated Analysis of Mooring and Riser Systems for FPSO’s in Harsh Shallow Water Environments
    Volume 4: Pipeline and Riser Technology, 2011
    Co-Authors: M Martens, J R Whelan, Y Drobyshevski
    Abstract:

    Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) Conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean Conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO Condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the Metocean Conditions, an offset envelope for each governing Metocean Condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated Metocean Conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.Copyright © 2011 by ASME

M Martens - One of the best experts on this subject based on the ideXlab platform.

  • integrated analysis of mooring and riser systems for fpso s in harsh shallow water environments
    ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering, 2011
    Co-Authors: M Martens, J R Whelan, Y Drobyshevski
    Abstract:

    Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) Conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean Conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO Condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the Metocean Conditions, an offset envelope for each governing Metocean Condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated Metocean Conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.Copyright © 2011 by ASME

  • Integrated Analysis of Mooring and Riser Systems for FPSO’s in Harsh Shallow Water Environments
    Volume 4: Pipeline and Riser Technology, 2011
    Co-Authors: M Martens, J R Whelan, Y Drobyshevski
    Abstract:

    Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) Conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean Conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO Condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the Metocean Conditions, an offset envelope for each governing Metocean Condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated Metocean Conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.Copyright © 2011 by ASME

J R Whelan - One of the best experts on this subject based on the ideXlab platform.

  • integrated analysis of mooring and riser systems for fpso s in harsh shallow water environments
    ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering, 2011
    Co-Authors: M Martens, J R Whelan, Y Drobyshevski
    Abstract:

    Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) Conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean Conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO Condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the Metocean Conditions, an offset envelope for each governing Metocean Condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated Metocean Conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.Copyright © 2011 by ASME

  • Integrated Analysis of Mooring and Riser Systems for FPSO’s in Harsh Shallow Water Environments
    Volume 4: Pipeline and Riser Technology, 2011
    Co-Authors: M Martens, J R Whelan, Y Drobyshevski
    Abstract:

    Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) Conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean Conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO Condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the Metocean Conditions, an offset envelope for each governing Metocean Condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated Metocean Conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.Copyright © 2011 by ASME

Vahid Jahangiri - One of the best experts on this subject based on the ideXlab platform.

  • Fatigue damage mitigation of offshore wind turbines under real wind and wave Conditions
    Engineering Structures, 2018
    Co-Authors: Vahid Jahangiri
    Abstract:

    Abstract Offshore wind turbines (OWTs) subjected to combined wind and wave loadings experience excessive vibrations which will increase fatigue loadings on the structure and reduce the fatigue life. In this paper, a three-dimensional pendulum tuned mass damper (3d-PTMD) is attached to the OWT to mitigate the bi-directional vibrations resulting from wind-wave misalignment so as to increase the fatigue life. An analytical model of the offshore wind turbine coupled with the 3d-PTMD is established using the Euler-Lagrangian equation. To predict long-term Metocean Condition, a statistical analysis for different properties of wind and wave loading such as, wind-wave misalignment, significant wave height and wind velocity is carried out. The aerodynamic wind loading is calculated using the blade element method and the wave loading is computed using the JONSWAP wave spectrum and Morison equation. Dual linear tuned mass dampers (TMDs) deployed in the side-side and fore-aft directions are used for comparison. The NREL monopile 5 MW baseline wind turbine is used to examine the performance of 3d-PTMD in a realistic Metocean Condition. The fatigue damage is estimated based on the rain-flow cycle counting method and Miner’s rule. Results indicate that the 3d-PTMD can increase the wind turbine tower fatigue life by more than 50% in comparison with the dual TMDs.

Arvid Naess - One of the best experts on this subject based on the ideXlab platform.

  • Short‐term extreme response analysis of a jacket supporting an offshore wind turbine
    Wind Energy, 2012
    Co-Authors: Nilanjan Saha, Torgeir Moan, Arvid Naess
    Abstract:

    Wind turbines must be designed in such a way that they can survive in extreme environmental Conditions. Therefore, it is important to accurately estimate the extreme design loads. This paper deals with a recently proposed method for obtaining short-term extreme values for the dynamic responses of offshore fixed wind turbines. The 5 MW NREL wind turbine is mounted on a jacket structure (92 m high) at a water depth of 70 m at a northern offshore site in the North Sea. The hub height is 67 m above tower base or top of the jacket, i.e. 89 m above mean water level. The turbine response is numerically obtained by using the aerodynamic software HAWC2 and the hydrodynamic software USFOS. Two critical responses are discussed, the base shear force and the bending moment at the bottom of the jacket. The extreme structural responses are considered for wave-induced and wind-induced loads for a 100 year return-period harsh Metocean Condition with a 14.0 m significant wave height, a 16 s peak spectral period, a 50 m s  − 1 (10 min average) wind speed (at the hub) and a turbulence intensity of 0.1 for a parked wind turbine. After performing the 10 min nonlinear dynamic simulations, a recently proposed extrapolation method is used for obtaining the extreme values of those responses over a period of 3 h. The sensitivity of the extremes to sample size is also studied. The extreme value statistics are estimated from the empirical mean upcrossing rates. This method together with other frequently used methods (i.e. the Weibull tail method and the global maxima method) is compared with the 3 h extreme values obtained directly from the time-domain simulations. Copyright © 2012 John Wiley & Sons, Ltd.