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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Ocean System Engineering
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Korean Society of Ocean Engineers
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Volume & Issues
Volume 4, Issue 1 - Feb 2014
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Hydrodynamic Responses of Spar Hull with Single and Double Heave Plates in Random Waves
Sudhakar, S. ; Nallayarasu, S. ;
International Journal of Ocean System Engineering, volume 4, issue 1, 2014, Pages 1~18
DOI : 10.5574/IJOSE.2014.4.1.001
Heave plates have been widely used to enhance viscous damping and thus reduces the heave response of Spar platforms. Single heave plate attached to the keel of the Spar has been reported in literature (Tao and Cai 2004). The effect of double heave plates on hydrodynamic response in random waves has been investigated in this study. The influence of relative spacing
-the diameter of the heave plate) on the hydrodynamic response in random waves has been simulated in wave basin experiments and numerical model. The experimental investigation has been carried out using 1:100 scale model of Spar with double heave plates in random waves for different relative spacing and varying wave period. The influence of relative spacing between the heave plates on the motion responses of Spar are evaluated and presented. Numerical investigation has been carried out to investigate effect of relative spacing on hydrodynamic characteristics such as heave added mass and hydrodynamic responses. The measured results were compared with those obtained from numerical simulation and found to be in good agreement. Experimental and numerical simulation shows that the damping coefficient and added mass does not increase for relative spacing of 0.4 and the effect greater than relative spacing on significant heave response is insignificant.
Influence of Tether Length in the Response Behavior of Square Tension Leg Platform in Regular Waves
El-gamal, Amr R. ; Essa, Ashraf ;
International Journal of Ocean System Engineering, volume 4, issue 1, 2014, Pages 19~28
DOI : 10.5574/IJOSE.2014.4.1.019
The tension leg platform (TLP) is a vertically moored structure with excess buoyancy. The TLP is regarded as moored structure in horizontal plan, while inherit stiffness of fixed platform in vertical plane. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of tethers length and wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e. 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether length, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about that is significantly dependent on tether length.
Implementation of a Joint System for Waves and Currents in the Black Sea
Toderascu, Robert ; Rusu, Eugen ;
International Journal of Ocean System Engineering, volume 4, issue 1, 2014, Pages 29~42
DOI : 10.5574/IJOSE.2014.4.1.029
The objective of this paper is to present the implementation of a joint modeling system able to evaluate the propagation of the polluting agents in the marine environment. The system is composed by circulation model (Mohid) and a spectral wave model (SWAN). The results coming from the circulation model are provided as input to the SWAN simulations. Following this target the Mohid water circulation model was implemented and calibrated in the Black Sea basin. The current simulations were run for one year (2010) with a time step of 24 hours, using wind fields from ECMWF. The results concerning the current fields were introduced into SWAN, and the difference between the results of the SWAN simulations with and without the current input from Mohid was assessed. In this regard, 10 points where the significant wave height difference is higher were considered and analyzed. The conclusion of the work is that such a joint system provides more reliable results concerning the wave and current conditions in the Black Sea as it is very useful in providing the support in the case of the environmental alerts that may occur in marine environments.
Numerical Analysis of Floating-Body Motions in Varying Bathymetry
Kim, Taeyoung ; Kim, Yonghawn ;
International Journal of Ocean System Engineering, volume 4, issue 1, 2014, Pages 43~48
DOI : 10.5574/IJOSE.2012.4.1.043
Varying bathymetry significantly affects on the wave propagation and motion response of floating body. Coupled-mode wave theory is adopted to describe the incident wave properly in varying region. The results of waves and motion response are compared to those from numerical wave tank, and the agreement is favorable. The sloped bottom is modeled and its effect on the floating body is discussed.
Development of Multidirectional Nonlinear Numerical Wave Tank by Naoe-FOAM-SJTU Solver
Cao, Hong-Jian ; Wan, De-Cheng ;
International Journal of Ocean System Engineering, volume 4, issue 1, 2014, Pages 49~56
DOI : 10.5574/IJOSE.2014.4.1.049
A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.