• Ocean Systems Engineering
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• v.7 no.4
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• pp.413-433
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• 2017

The dynamic and structural responses of a 1000-m long circular submerged floating tunnel (SFT) with both ends fixed under survival irregular-wave excitations are investigated. The floater-mooring nonlinear and elastic coupled dynamics are modeled by a time-domain numerical simulation program, OrcaFlex. Two configurations of mooring lines i.e., vertical mooring (VM) and inclined mooring (IM), and four different buoyancy-weight ratios (BWRs) are selected to compare their global performances. The result of modal analysis is included to investigate the role of the respective natural frequencies and elastic modes. The effects of various submergence depths are also checked. The envelopes of the maximum/minimum horizontal and vertical responses, accelerations, mooring tensions, and shear forces/bending moments of the entire SFT along the longitudinal direction are obtained. In addition, at the mid-section, the time series and the corresponding spectra of those parameters are also presented and analyzed. The pros and cons of the two mooring shapes and high or low BWR values are systematically analyzed and discussed. It is demonstrated that the time-domain numerical simulation of the real system including nonlinear hydro-elastic dynamics coupled with nonlinear mooring dynamics is a good method to determine various design parameters.

• Nuclear Engineering and Technology
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• v.30 no.2
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• pp.164-172
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• 1998

This paper presents the detailed modelling of reactor vessel ledge region for the dynamic analysis of the coupled internals and core model. The dynamic responses due to earthquake and pipe break are calculated using the input motions of reactor vessel taken from Ulchin nuclear power plant units 3 and 4. Two different representations for detailed and simplified models of the RV ledge region are made. The dynamic responses of the reactor internals components are compared between them. Response characteristics are reported and simplified model is suggested for earthquake and pipe break analysis for the future design of the reactor internals.

• Journal of Ship and Ocean Technology
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• v.6 no.3
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• pp.13-25
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• 2002

In this paper, the motion responses with hydrodynamic interaction effect between two off-shore floating structures in various heading waves are studied by using a linearized three-dimensional potential theory. Numerical calculations using three-dimensional pulsating source distribution techniques have been carried out for twelve coupled linear motion responses and relative motions of the barge and the ship in oblique waves. The computational results give a good correlation with the experimental results and also with other numerical results. As a result, the present computational tool can be used effectively to predict the motion responses of multiple offshore floating structures in waves.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.2
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• pp.87-93
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• 2020

Seismic responses due to the dynamic coupling between a primary structure and secondary system connected to a structure are analyzed in this study. The seismic responses are compared based on dynamic coupling criteria and according to the error level in the natural frequency, with the recent criteria being reliant on the error level in the spectral displacement response. The acceleration responses and relative displacement responses of a primary structure and a secondary system for a coupled model and two different decoupled models of two degrees-of-freedom system are calculated by means of the time integration method. Errors in seismic responses of the uncoupled models are reduced with the recent criteria. As the natural frequency of the secondary system increases, error in the natural frequency decreases, but seismic responses of uncoupled models can be underestimated compared to that of coupled model. Results in this paper can help determine dynamic coupling and predict uncoupled models' response conservatism.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.8
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• pp.764-772
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• 2009

In this study, fluid/structure coupled analyses have been conducted for 3-D stator and rotor configuration. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics(CSD) has been developed in order to investigate fluid/structure responses of general stator-rotor configurations. To solve the fluid/structure coupled problems, fluid domains are modeled using the structural grid system with dynamic moving and local deforming techniques. Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras(S-A) and SST ${\kappa}-{\omega}$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3-D turbine blades for fluid-structure interaction(FSI) problems. Detailed fluid/structure analysis responses for stator-rotor interaction flow conditions are presented to show the physical performance and flow characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.563-569
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• 2008

In this study, fluid/structure coupled analyses have been conducted f3r 3-D stator and rotor configuration. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate fluid/structure responses of general stator-rotor configurations. To solve the fluid/structure coupled problems, fluid domains are modeled using the structural grid system with dynamic moving and local deforming techniques. Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras (S-A) and SST ${\kappa}-{\omega}$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3-D turbine blades for fluid-structure interaction (FSI) problems. Detailed fluid/structure analysis responses for stator-rotor interaction flow conditions are presented to show the physical performance and flow characteristics.

• Ocean Systems Engineering
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• v.1 no.1
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• pp.95-111
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• 2011

Increasing numbers of floating offshore wind turbines are planned and designed these days due to their high potential in massive generation of clean energy from water depth deeper than 50 m. In the present study, a numerical prediction tool has been developed for the fully-coupled dynamic analysis of FOWTs in time domain including aero-blade-tower dynamics and control, mooring dynamics, and platform motions. In particular, the focus of the present study is paid to the dynamic coupling between the rotor and floater and the coupled case is compared against the uncoupled case so that their dynamic coupling effects can be identified. For this purpose, a mono-column mini TLP with 1.5MW turbine for 80m water depth is selected as an example. The time histories and spectra of the FOWT motions and accelerations as well as tether top-tensions are presented for the given collinear wind-wave condition. When compared with the uncoupled analysis, both standard deviations and maximum values of the floater-responses/tower-accelerations and tether tensions are appreciably increased as a result of the rotor-floater dynamic coupling, which may influence the overall design including fatigue-life estimation especially when larger blades are to be used.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.443-450
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• 2000

In this study a numerical method for soil-pile interaction analysis buried in multi-layered half planes is presented in frequency domain using FE-BE coupling. The total soil-pile interaction system is divided into two parts so called far field and near field beam elements are used for modeling a pile and coupled with plain strain elements for soil modeling. Boundary element formulation using the multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered half-planes are performed and compared with experiment results. Through this developed method the dynamic response analysis of a pile buried in multi-layered half planes can be calculated effectively in frequency domain.

• Coupled systems mechanics
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• v.1 no.1
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• pp.79-98
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• 2012

In the present paper, the three-dimensional model of a typical rectangular concrete tank is excited using an artificial and a natural three components earthquake ground motion and the staggered displacement method is utilized for solving the coupled problem of the tank-contained liquid system in time domain. In the proposed method, surface sloshing of the liquid is taken into account in addition to the impulsive term and the appropriate damping values are applied on both of them. The resulted responses are compared with those obtained from the ABAQUS finite element software. It is found that the convective term affects responses extensively and must be considered in seismic design/safety assessment of storage tanks. In addition, the utilized method for solving the coupled problem is stable during the conducted general dynamic analyses and is able to capture the expected phenomena.

• Ocean Systems Engineering
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• v.8 no.4
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• pp.441-459
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• 2018

A coupled dynamic analysis of a semisubmersible-type FOWT has been carried out in time domain under the combined action of irregular wave and turbulent wind represented respectively by JONSWAP spectrum and Kaimal spectrum. To account for the turbine-floater motion coupling in a more realistic way, the wind turbulence has been incorporated into the calculation of aerodynamic loads. The platform model was referred from the DeepCwind project and the turbine considered here was the NREL 5MW Baseline. To account for the operationality of the turbine, two different environmental conditions (operational and survival) have been considered and the aerodynamic effect of turbine-rotation on actual responses of the FOWT has been studied. Higher mean offsets in surge and pitch responses were obtained under the operational condition as compared to the survival condition. The mooring line tensions were also observed to be sensitive to the rotation of turbine due to the turbulence of wind and overestimated responses were found when the constant wind was considered in the analysis. Additionally, a special analysis case of sudden shutdown of the turbine has also been considered to study the swift modification of responses and tension in the mooring cables.