Experimental Study on Application of an Optical Sensor to Measure Mooring-Line Tension in Waves (original) (raw)
2022, Journal of Ocean Engineering and Technology
A moored floating platform has great potential in ocean engineering applications because a mooring system is necessary to keep the floating platform in station. In order to do this, the tension of the mooring line is investigated to ensure its bearing capacity. Kim et al. (2005) investigated the mooring dynamics in wind, waves, and currents through a simulation and experiment. In addition, the mooring tension from the simulation's results was compared with experimental results. The effect of the position of the mooring line on the dynamic responses of the spar platforms was studied by Montasir et al. (2015). The platform was connected with asymmetric and symmetric mooring configurations. The dynamic responses of the spar were estimated based on the tension of the mooring lines. Natarajan and Ganapathy (1997) performed a model test on a moored ship to measure the tension of the mooring lines. The model test was carried out with two types of the mooring configurations: spread mooring and berth mooring. The experiment was performed in head sea in various environmental conditions of wind, waves, and current. Other studies on the hydrodynamic characteristics of a moored platform in freak waves were conducted (Pan et al., 2018; Pan et al., 2021). The tension of the mooring line response was increased significantly under the effect of freak waves. In addition, the dynamic response and the tension of the mooring line in the freak waves were compared to that in irregular waves. Cevasco et at. (2018) studied the dynamic response of a floating offshore wind turbine system by conducting a numerical simulation. Two different versions of the mooring dynamics were compared. Paduano et at. (2020) conducted an experiment and
Related papers
Dynamics of mooring systems in ocean engineering
Archive of Applied Mechanics (Ingenieur Archiv), 2003
The computation of restoring forces on floating platforms caused by mooring systems in ocean engineering is usually performed by means of quasi-static procedures. Thereby, nonlinear phenomena produced by the motion of the mooring line or the interaction between fluid and line are not considered. For lines in deep water, these effects may cause a tremendous increase in the tension force, which cannot be predicted by simplified models. Therefore, it is mandatory to determine the dynamics by means of a more precise mathematical model. In this paper, a model is presented for the analysis of the dynamic behavior of mooring systems taking into account the hydrodynamic forces exerted by the surrounding fluid. The mathematical description of the real mooring line is performed using a multibody system approach. Furthermore, a comparison of results of a quasi-static and a dynamic analysis is presented in order to stress the importance of a dynamic analysis of mooring lines.
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, 2004
A combined experimental/numerical investigation of a moored floating structure response to incoming waves to incoming waves is proposed. The floating structure consists of three bodies, equipped with fenders, joined by elastic cables. The system is also moored to the seabed with eight mooring lines. This corresponds to an actual configuration of a floating structure used for ships and submarines in special docking operations. The dynamic wave response is investigated by performing experiments in a towing tank equipped with a wave maker. Experimental results are compared with numerical simulations in regular and irregular waves, showing a good agreement. In regular waves the predicted time histories of pitch, heave and surge motions of the three-body structure and of the mooring line forces, bear very satisfactorily the experimental results. The case of irregular waves is also encouraging, since the statistics of the response is correctly kept up to the fourth order statistical moments. This confirms that the theoretical model proposed in this paper is a suitable tool to predict the actual behaviour of a complex moored structure at sea.
Expansion of Design Static Properties analysis of mooring system for Offshore Floating Wind Turbine
As for all other floating structures operating within a limited area, station keeping is needed in order to keep the motions of the floating structure within permissible limits. In this study, methods for selecting and optimizing the mooring system Caisson for floating wind turbines in shallow water are investigated. The design of the mooring system is checked against the governing rules and standards. Verifying the design of floating structures adequately requires both numerical simulations and model testing, a combination of which is referred to as the hybrid method of design verification. The challenge in direct scaling of moorings for model tests is the depth and spatial limitations in wave basins. It is therefore important to design and build equivalent mooring systems to ensure that the static properties (global restoring forces and global stiffness).
Dynamic Response of Coupled Mooring Lines and Floating Wave Energy Devices in Waves / Currents
International Journal of Innovative Technology and Exploring Engineering, 2019
Various global studies have shown that ocean waves energy have large potential in renewable energy sector. Their role within renewable energy gets high priority in the future by the government of United Kingdom. The principle concept of wave energy is when wave energy is converted into potential energy by the wave energy devices to generate electricity. An understanding of the dynamic response of the devices and mooring lines is important for this paper. This paper deals with the analysis of the various effects that influence the different design of wave energy converter devices. The mooring design idea is also analyzed to show which mooring layout is suitable to fulfill the requirement. The design of mooring configuration also influence how wave power is extracted and how such system are operated and maintained. The effects investigated in this paper are regular and irregular waves, motion @ six degrees of freedom, maximum and minimum mooring tension, different waves direction, wav...
Ships and Offshore Structures, 2020
A reliable simulation model to calculate the motion and force responses of wave energy converters (WECs) is imperative to ensure the reliability and long-term performance of WEC systems; these aspects are fundamental to achieving full commercialisation of wave energy. A simulation model was developed and validated concerning the simulated WEC buoy motions in a previous study; this study validated the mooring force calculations for the same model. The example WEC system comprises a buoy, a power takeoff (PTO) system, and a three-leg mooring system wherein each leg is divided into two taut segments joined by a submerged float. A 1:20 physical model was built and tested in the Deepwater Offshore Basin at Shanghai Jiao Tong University. Numerical models were developed to simulate the coupled hydrodynamic and structural responses of the WEC system, primarily using potential flow theory, the boundary element method, the finite element method, and the Morison equation. The simulated and measured axial force results at the top ends of the six mooring segments were compared; the results agreed best in the lower segments of each mooring leg and in the moorings on the downwind side because of the PTO system uncertainties and the uncalibrated damping in the numerical model. Nonetheless, the numerical model reasonably predicted the moorings' accumulated fatigue damage, demonstrating that the model can be reliably used for mooring structural analyses. The study also used the validated numerical model to simulate a full-scale WEC system installed in Runde, Norway. A comparison of the results from the full-scale measurements and simulations shows that the numerical simulation model exhibited a good predictive capability for the mooring forces of the full-scale WEC system.
A Method for Computational and Experimental Analysis of the Moored Wind Turbine Seakeeping
2012
The paper presents a proposal of the method for analysis of the moored wind turbine’s float seakeeping, elaborated by Ship Design and Research Centre S.A. for the purpose of the project realized for VISTAL WIND POWER Ltd. The analysis started with preliminary seakeeping prediction realized with the use of CFD solver coupled with 6DOF module, in which the sliding mesh approach was used to handle the moving object. The numerical analysis included modelling the characteristics of the mooring tethers with equivalent force approach (such an approach was presented e.g. by Pascoal et al. [1]). Evaluation of the tether characteristics was realized numerically with the use of lumped mass method. As the results of numerical study revealed satisfactory performance of the proposed wind turbine float design, further experimental tests of the physical model of the float were realized. The mooring tethers were modelled by direct scaling of the full scale tethers, which prevented truncation errors ...
2014
Exposure to environmental conditions at sea for floating structures is inevitable. Environmental conditions that waves are most important of them will enter forces on structure of semi-submersible platforms. Therefore such structures should be deployed in the operational capability of their own, that one of these methods is mooring them. In this condition, structure shows different behavior compared with unmoored structure. Wave force cause motions of structure and subsequently produce tension force on mooring lines. Hence, investigation of structure movements and selection an appropriate mooring system to minimizing the structure motions must have been discussed. semi-submersible platforms mooring systems results restoring force in horizontal plane, and thus control degree of freedom on Surge, Sway and Yaw movements. This study estimated Surge and Sway movements of a semi-submersible platform when that it has been exposed to 0, 45 and 90 degrees of sea wave direction with the envir...
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.