The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform

Zhiqiang Hu - One of the best experts on this subject based on the ideXlab platform.

  • dynamic Response and viscous effect analysis of a tlp type floating wind turbine using a coupled aero hydro mooring dynamic code
    Renewable Energy, 2016
    Co-Authors: Macheng Shen, Zhiqiang Hu
    Abstract:

    This paper presents a coupled dynamic motion Response analysis of a floating wind turbine using an in-house code, CRAFT (Coupled Response Analysis of Floating wind Turbine). Viscous drag forces on horizontal pontoons are carefully calculated, and a nonlinear spectral method is applied to efficiently solve the coupled tendon dynamics. Viscous drag forces and tendon dynamics are two important factors when assessing a tension-leg platform (TLP)-type floating wind turbine in a time-domain simulator. The analysis object is the NREL 5 MW Wind Turbine, which is supported by a three-leg mini-TLP platform. Simulations of the free decay and Response Amplitude Operator (RAO) tests are conducted using CRAFT as well as FAST, another commonly used code. The obtained results are compared with experimental results to verify the capability of CRAFT. Viscous drag force induces higher harmonic pitch resonance, which is most prominent when the wave period is three times the natural period of the pitch and the wave height reaches a threshold. Springing motion is identified and found to be caused by this resonant pitch motion. Time-domain statistics show that extreme increases in tendon loads caused by springing as well as pitch and tendon tension probability distributions are non-Gaussian in random sea states. In addition, the resonant pitch motion is significantly reduced by aerodynamic damping.

  • Numerical and Model Test Investigation on the Motion Characteristic of FDPSO and the Sheltered Riser Vessel
    29th International Conference on Ocean Offshore and Arctic Engineering: Volume 1, 2010
    Co-Authors: Zhiqiang Hu, Gang Chen, Jianmin Yang
    Abstract:

    FDPSO is a multifunction floating platform, capable of drilling, production, storage and offloading. Sheltered Riser Vessel (SRV) serves as an independent buoyant hull to provide riser tensions, which is situated in the moon pool of FDPSO. Due to the shielding effect of moon pool, the motion of SRV is very small, so as to meet the requirement of drilling. In order to validate the basic FDPSO and SRV concepts, a model test was conducted in the basin of Ocean Engineering in the State Key Lab of Ocean Engineering in Shanghai Jiao Tong University. The storm tests were carried out in wave extremes of West Africa and white noise wave environments. Potential theory was adopted to calculate the motion performance of FDPSO system. Frequency domain analysis of the motion Response Amplitude Operator (RAO) and time domain analysis in the extreme sea condition are both conducted. The comparison between the numerical simulation and model test results shows that the results of RAO and statistical value of Response time series in the extreme sea condition are coincident. It is indicate that the method is credible and the concepts of FDPSO and SRV are likely to be feasible in West Africa.Copyright © 2010 by ASME

Macheng Shen - One of the best experts on this subject based on the ideXlab platform.

  • dynamic Response and viscous effect analysis of a tlp type floating wind turbine using a coupled aero hydro mooring dynamic code
    Renewable Energy, 2016
    Co-Authors: Macheng Shen, Zhiqiang Hu
    Abstract:

    This paper presents a coupled dynamic motion Response analysis of a floating wind turbine using an in-house code, CRAFT (Coupled Response Analysis of Floating wind Turbine). Viscous drag forces on horizontal pontoons are carefully calculated, and a nonlinear spectral method is applied to efficiently solve the coupled tendon dynamics. Viscous drag forces and tendon dynamics are two important factors when assessing a tension-leg platform (TLP)-type floating wind turbine in a time-domain simulator. The analysis object is the NREL 5 MW Wind Turbine, which is supported by a three-leg mini-TLP platform. Simulations of the free decay and Response Amplitude Operator (RAO) tests are conducted using CRAFT as well as FAST, another commonly used code. The obtained results are compared with experimental results to verify the capability of CRAFT. Viscous drag force induces higher harmonic pitch resonance, which is most prominent when the wave period is three times the natural period of the pitch and the wave height reaches a threshold. Springing motion is identified and found to be caused by this resonant pitch motion. Time-domain statistics show that extreme increases in tendon loads caused by springing as well as pitch and tendon tension probability distributions are non-Gaussian in random sea states. In addition, the resonant pitch motion is significantly reduced by aerodynamic damping.

Mohammad Javad Ketabdari - One of the best experts on this subject based on the ideXlab platform.

  • Experimental Study on the Response Behaviour of SeaStar Mini Tension Leg Platform Against Random Water Waves
    Volume 1: Offshore Technology; Special Symposium on Ocean Measurements and Their Influence on Design, 2007
    Co-Authors: Hamid Alemi Ardakani, Mohammad Javad Ketabdari
    Abstract:

    Among the compliant platforms, TLP is a vertically moored structure with excess buoyancy, used for deep water oil exploration. In this structure tethers can be tensioned to such an extent that heave, roll and pitch motions of the platform induced by ocean waves are virtually eliminated. SeaStar is new generation of mini tension leg platforms which is similar to a spar and has favorable Response features of a TLP. This paper illustrates the results of experimental work performed on a 1/100 scaled model of SeaStar TLP in a wave flume. The study refers to the induced tension in different tendons of the model and the motion Response behaviour of the model on different degrees of freedom under several directional impinging random water waves. The results are presented in the frequency domain and the Response Amplitude Operator for each motion of the platform has been calculated.Copyright © 2007 by ASME

  • Laboratory Investigation on Response Behaviour of SeaStar Mini Tension Leg Platform Against Regular Water Waves
    Volume 4: Materials Technology; Ocean Engineering, 2007
    Co-Authors: Mohammad Javad Ketabdari, Hamid Alemi Ardakani, Mohammad Alemi Ardakani
    Abstract:

    Among the compliant platforms, TLP is a vertically moored structure with excess buoyancy, used for deep water oil exploration. In this structure tethers can be tensioned to such an extent that heave, roll and pitch motions of the platform induced by ocean waves are virtually eliminated. SeaStar is new generation of mini tension leg platforms which is similar to a spar and has favorable Response features of a TLP. This paper illustrates the results of experimental work performed on a 1/100 scaled model of SeaStar TLP in a wave flume. The investigation refers to the induced tension in different tendons of the model and the motion Response behaviour of the model on different degrees of freedom under several directional impinging regular water waves. The results are presented in the frequency domain and the Response Amplitude Operator for each motion of the platform has been calculated.Copyright © 2007 by ASME

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

  • Numerical investigation on dynamic Responses of classic spar platforms: Long crested waves vs. short crested waves
    2012 IEEE Colloquium on Humanities Science and Engineering (CHUSER), 2012
    Co-Authors: V. J. Kurian, C. Y. Ng, M. S. Liew
    Abstract:

    In the real sea condition, only multi-directional waves or short crested waves are found. Short crested wave isdefined as thelinear summation of various long crested waves propagated to various angles, where the magnitude and direction generated are randomly varied. In this study, the dynamic Responses of classic spar platform subjected to long crested and short crested waves are investigated numerically and compared. Two numerical simulations are developed by incorporating Diffraction theory to obtain the wave forces for long crested waves and short crested waves. The classic spar platform is assumed to be rigid with three degrees of freedom surge, heave and pitch, restrained by four mooring lines. For every time step, the mass, damping and stiffness matrices are evaluated. The equations of motion are formulated for the platform dynamic equilibrium and are solved by using Newmark Beta method in time domain. The results in terms of Response Amplitude Operator (RAO) for surge, heave and pitch motionsare obtained and compared.

  • Dynamic Responses of classic spar platforms subjected to long crested waves: Morison equation vs. Diffraction theory
    2012 International Conference on Statistics in Science Business and Engineering (ICSSBE), 2012
    Co-Authors: V. J. Kurian, C. Y. Ng, M. S. Liew
    Abstract:

    Morison equation, Froude Krylov theory and Diffraction theory are the common theories used to evaluate the wave force for offshore structures. The applicability of these theories is based upon the type and size of the member of the structures. Morison equation is normally used for small structures compared to wave length, while for large structures Diffraction theory needs to be applied. However, in many cases Morison equation has been used to obtain the wave forces for classic spars, which are large offshore structures installed in deepwater. This paper presents the results of numerical investigation of an offshore classic spar platform subjected to long crested waves. Two numerical simulations were developed by incorporating the Morison equation and Diffraction theory to obtain the wave forces. The classic spar was modeled as a rigid body with three degrees of freedom restrained by mooring lines. In the simulation, the mass, damping and stiffness matrices were evaluated at every time step. The equations of motion were formulated for the platform dynamic equilibrium and solved by using Newmark Beta method. The results were obtained in terms of Response Amplitude Operator (RAO) for surge, heave and pitch motions. The dynamic Responses obtained were compared.

Allan C. De Oliveira - One of the best experts on this subject based on the ideXlab platform.

  • MPSO Design: Part 1 — Wave Excitation Forces and Moments
    Volume 1: Offshore Technology, 2012
    Co-Authors: Daniel Prata Vieira, Edgard Borges Malta, Rafael A. Watai, Rodolfo T. Gonçalves, André L. C. Fujarra, Kazuo Nishimoto, Allan C. De Oliveira
    Abstract:

    The MPSO is characterized by the use of hydrodynamics appendages, such as moonpool, beach and skirts, which improve the hydrodynamic behavior of the unit in waves. This type of platform may be designed for different offshore scenarios as, for example: the possibility of oil and gas storage, dry tree completion system and the use of steel catenary risers (SCR). An optimization procedure to choose the geometric dimensions of the MPSO becomes important in order to achieve the optimum hydrodynamic behavior to operate in harsh environmental conditions for each scenario. The optimization procedure might be useful in the preliminary design phases to reduce the verification time of the solution evaluated with model tests; for that reason it is necessary to create a database with experimental results to make the optimization procedure possible. The main idea of the study is to carry out an extensive experimental model test aimed at obtaining the parameters not well predicted using numerical codes. With this intent, the work is subdivided into three parts: Part 1 – Wave Excitation Forces and Moments; Part 2 – Damping and Added Mass Forces and Part 3 – Optimization Process. Results will be presented in different papers. The first one presents the experimental results for captive tests, the second one the experimental results for forced oscillation tests and the last one the methodology to use the experimental results as input in an optimization tool. The first paper presents the methodology in which nondimensional variables based on MPSO geometric characteristics were defined. These variables were related to a fixed moonpool diameter and they were determined in terms of four geometric dimensions: external diameter; height and diameter of the beach and platform draft. As a consequence, 21 different MPSO model geometries could be defined and experimentally tested in order to obtain the wave excitation forces and moments in 6 DOF. The experiments included transient waves so as to better understand the hydrodynamic behavior of the hull, such as, the Response Amplitude Operator (RAO), cancelation points, the beach/bottom/moonpool effects for the different dimensions. The wave forces and moments obtained experimentally were compared to the results of a numerical code based on potential wave theory.Copyright © 2012 by ASME

  • mpso design part 1 wave excitation forces and moments
    ASME 2012 31st International Conference on Ocean Offshore and Arctic Engineering, 2012
    Co-Authors: Daniel Prata Vieira, Edgard Borges Malta, Rafael A. Watai, Rodolfo T. Gonçalves, André L. C. Fujarra, Kazuo Nishimoto, Allan C. De Oliveira
    Abstract:

    The MPSO is characterized by the use of hydrodynamics appendages, such as moonpool, beach and skirts, which improve the hydrodynamic behavior of the unit in waves. This type of platform may be designed for different offshore scenarios as, for example: the possibility of oil and gas storage, dry tree completion system and the use of steel catenary risers (SCR). An optimization procedure to choose the geometric dimensions of the MPSO becomes important in order to achieve the optimum hydrodynamic behavior to operate in harsh environmental conditions for each scenario. The optimization procedure might be useful in the preliminary design phases to reduce the verification time of the solution evaluated with model tests; for that reason it is necessary to create a database with experimental results to make the optimization procedure possible. The main idea of the study is to carry out an extensive experimental model test aimed at obtaining the parameters not well predicted using numerical codes. With this intent, the work is subdivided into three parts: Part 1 – Wave Excitation Forces and Moments; Part 2 – Damping and Added Mass Forces and Part 3 – Optimization Process. Results will be presented in different papers. The first one presents the experimental results for captive tests, the second one the experimental results for forced oscillation tests and the last one the methodology to use the experimental results as input in an optimization tool. The first paper presents the methodology in which nondimensional variables based on MPSO geometric characteristics were defined. These variables were related to a fixed moonpool diameter and they were determined in terms of four geometric dimensions: external diameter; height and diameter of the beach and platform draft. As a consequence, 21 different MPSO model geometries could be defined and experimentally tested in order to obtain the wave excitation forces and moments in 6 DOF. The experiments included transient waves so as to better understand the hydrodynamic behavior of the hull, such as, the Response Amplitude Operator (RAO), cancelation points, the beach/bottom/moonpool effects for the different dimensions. The wave forces and moments obtained experimentally were compared to the results of a numerical code based on potential wave theory.Copyright © 2012 by ASME