• Journal of Ocean Engineering and Technology
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• v.28 no.6
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• pp.508-516
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• 2014

A numerical method to investigate the non-linear motion characteristics of a TLP is established. A time domain simulation that includes the memory effect using the convolution integral is used to consider the transient effect of TLP motion. The hydrodynamic coefficients and wave force are calculated using a potential flow model based on the HOBEM(higher order boundary element method). The viscous drag force acting on the platform and tendons is also considered by using Morison’s drag. The results of the present numerical method are compared with experimental data. The focus is the nonlinear effect due to the viscous drag force on the TLP motion. The ringing, springing, and drift motion are due to the drag force based on Morison's formula.

• Journal of Power System Engineering
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• v.16 no.1
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• pp.65-71
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• 2012

A numerical procedure is described for predicting the dynamic structural responses of tension leg platforms(TLPs) in current and waves. The developed numerical approach is based on a combination of the three dimensional source distribution method and the dynamic structural analysis method, in which the superstructure of the TLPs is assumed to be flexible instead of rigid. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in the dynamic structural analysis. The equations of motion of a whole structure are formulated using element-fixed coordinate systems which have the origin at the nodes of the each hull element and move parallel to a space-fixed coordinate system. The dynamic structural responses of a TLP were analyzed in the case of including the current or not including the one in waves and the effects of current on the TLP were investigated.

• Journal of Powder Materials
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• v.9 no.3
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• pp.189-198
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• 2002

In this work, transient liquid phase (TLP) bonding of Ni-Cr heat resisted cast alloy (HP) was investigated. And also the behaviors of the solid particles distributed in the interlayer during TLP bonding were investigated. The MBF-60 and solid particles (Ni, Fe, and $Al_2O_3$ powders respectively) added MBF-60 which will be a liquid phase coexisting with solid particles at the bonding temperature were used as insert metal. The effective and sound bonding was possible by spark plasma sinter-bonding due to the differences of electric resistance between base metal and liquid insert layer which creates high temperature region. During the isothermal solidification, $Al_2O_3$ particles and solid particles of liquid phase sintered insert metal have shown no growth, while Ni and Fe particles grow rapidly. In this TLP bonding using the MBF-60 and distributed Fe, Ni particles as insert materials, the whole isothermal solidification process was dominated by the growth rate of the solid particles distributed in the interlayer.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.38.2-38.2
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• 2011

A large number of offshore wind turbines with fixed foundations have been installed in water depths up to 30 meters supporting 3-5MW wind turbines. Some floating platform concepts of offshore wind turbines were designed to be suitable for deployment in water depths greater than 60 meters. However the optimal design of this system in water depth 50 meters remains unknown. In this paper, a 5-MW wind turbine located on a TLP type platform was suggested for installation in this water depth. It is moored by a taut mooring line. For controlling the wind turbine always be operated at the upwind direction, one yaw controlling was attached at the tower. To study motion characteristics of this platform, a model was built with a 1/128 scale ratio. The model test was carried out in various conditions, including waves, winds and rotating rotor effect in the Ocean Engineering Wide Tank of the University Of Ulsan (UOU). The characteristic motions of the TLP platform were captured and the effective RAOs were obtained.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.385-407
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• 2015

This paper deals with the problem of the global stabilization for a class of tension leg platform (TLP) nonlinear control systems. It is well known that, in general, the global asymptotic stability of the TLP subsystems does not imply the global asymptotic stability of the composite closed-loop system. Finding system parameters for stabilizing the control system is also an issue need to be concerned. In this paper, we give additional sufficient conditions for the global stabilization of a TLP nonlinear system. In particular, we consider a class of NN based Takagi-Sugeno (TS) fuzzy TLP systems. Using the so-called parallel distributed compensation (PDC) controller, we prove that this class of systems can be globally asymptotically stable. The proper design of system parameters are found by a swarm intelligence algorithm called Evolved Bat Algorithm (EBA). An illustrative example is given to show the applicability of the main result.

• Korean Journal of Medicinal Crop Science
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• v.20 no.1
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• pp.36-41
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• 2012

This study was carried out to establish a proper cultivation site and diagnose the drought tolerance of Pleurospermum camtschaticum, Cirsium setidens and Parasenecio firmus leaves by using pressure-volume curves. The result of ${\Psi}_o^{sat}$ and ${\Psi}_o^{tlp}$ were lower in Pleurospermum camtschaticum leaves. On the other hand, it appeared that $E_{max}$ of Pleurospermum camtschaticum was approximately six times higher than that of Parasenecio firmus. The values of $RWC^{tlp}$ is all above 88% showing that the function of osmoregulation is somewhat better, and Vo/DW, Vt/DW, Ns/DW of Pleurospermum camtschaticum leaves were approximately 2~4 times Lower than other ones. Thus, responses to water relations of Pleurospermum camtschaticum, Cirsium setidens and Parasenecio firmus such as ${\Psi}_o^{sat}$, ${\Psi}_o^{tlp}$, $E_{max}$, ${\Psi}_{P,max}$, $RWC^{tlp}$ were shown that the Pleurospermum camtschaticum leave was higher drought tolerance than Cirsium setidens and Parasenecio firmus leaves.

• International Journal of Naval Architecture and Ocean Engineering
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• v.1 no.1
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• pp.13-19
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• 2009

The primary objective of this paper is to investigate the dynamic stability and survivability of a four-column classic TLP (tension-leg platform) under less-than-extreme storm conditions where one or more tendons have been lost due to damage or disconnect. The transient responses of the platform and tendon tensions at the moment of disconnection are particularly underscored. The numerical simulation is based on the BE-FE hybrid hull-tendon-riser coupled dynamic analysis in time domain. Compared to the common industry practice of checking the system without a failed tendon in the beginning, the maximum tension on the neighboring tendon can be significantly increased at the moment of disconnection due to the snap-like transient effects, which can lead to unexpected failure of the total system. It is also found that the transient effects can be reduced with the presence of TTRs (top-tensioned risers) with pneumatic tensioners. It is also seen that the TLP cannot survive in the 100-yr hurricane condition after losing one tendon.

• Journal of Practical Agriculture & Fisheries Research
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• v.19 no.1
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• pp.91-97
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• 2017

This study was carried out to establish a proper cultivation site and to diagnose the drought tolerance of Heracleum moellendorffii leaves by using pressure-volume curves. As a result of analysing data measured, the leaf of H. moellendorffii showed the osmotic pressure at full turgor (Ψ_o^sat) was -1.0MPa, and that at incipient plasmolysis (Ψ_o^tlp) -1.2MPa. Then, the value of maximum bulk modulus of elasticity Emax was 28MPa, showing the sightly strong drought tolerance of H. moellendorffii. Furthermore, the values of relative water contents RWC^tlp and RWC^* were above 88%, showing that the function of osmoregulation is somewhat better. Thus, responses to water relations such as Ψ_o^sat, Ψ_o^tlp, E_max, RWC^tlp and RWC^* of H. moellendorffii showed it's slightly high drought tolerance property.

• Ocean Systems Engineering
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• v.4 no.4
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• pp.327-342
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• 2014

The tension leg platform (TLP) is one of the compliant structures which are generally used for deep water oil exploration. With respect to the horizontal degrees of freedom, it behaves like a floating structure moored by vertical tethers which are pretension due to the excess buoyancy of the platform, whereas with respect to the vertical degrees of freedom, it is stiff and resembles a fixed structure and is not allowed to float freely. In the current study, a numerical study for square TLP using modified Morison equation was carried out in the time domain with water particle kinematics using Airy's linear wave theory to investigate the effect of changing the tether tension force on the stiffness matrix of TLP's, the dynamic behavior of TLP's; and on the fatigue stresses in the cables. The effect was investigated for different parameters of the hydrodynamic forces such as wave periods, and wave heights. The numerical study takes into consideration the effect of coupling between various degrees of freedom. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables. Nonlinear equation was solved using Newmark's beta integration method. 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 tension force, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations that is significantly dependent on wave height, and that special attention should be given to tethers fatigue because of their high tensile static and dynamic stress.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.223-228
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• 1987

An efficient method for the calculation of wave forces on a tension leg platform(TLP) is presented in this paper. It is based on the Morison's equation with two corrective terms. One is the reduction of the inertia forces on the vertical columns in order to include the wave diffraction effect particularly for small wave conditions. The other is the inclusion of the hydrodynamic forces acting at the bottoms of the columns. Numerical studies are carried out for a TLP in 1000 ft water with two different wave heading angles($0^{\circ}$ and $45^{\circ}$). The reponse amplitude operators(RAO's) for the TLP motions and top tether tension variations are obtained by the present method and the theoretically more accurate method based on the diffraction theory. A comparison has been made between the results obtained by two methods.