Theoretical and Experimental Investigations of Large Amplitude Ship Motions and Loads in Regular Head Seas PDF Download
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Author: Zhixiang Tao
Publisher:
ISBN:
Category : Ships
Languages : en
Pages :
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Author: Zhixiang Tao
Publisher:
ISBN:
Category : Ships
Languages : en
Pages :
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Author: Jean Otto de Kat
Publisher:
ISBN:
Category :
Languages : en
Pages : 668
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Author: Olgun Guven Hizir
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This PhD thesis presents the development of a practical computational tool named Large Amplitude RESponse (LARes), based on 3D quasi-non-linear time-domain technique, to predict ship motions and loads in large amplitude waves which can be accessible to ship designers. Firstly, a linear 3-D Green source panel code (LARes L1) was developed to perform linear time-domain analysis ship motion and internal load simulations based on the frequency-domain hydrodynamic coefficients which were calculated in the linear PRECAL software. Linear simulations are validated with the linear time-domain PRETTI software results using rectangular barge geometry. The motions, internal loads, global and sectional hydrodynamic forces were agreed well with the linear PRETTI model results in zero and forward speed simulations. Then, non-linear time-domain panel code (LARes L2) was developed in order to predict ship motions and loads in large amplitude waves using the Froude-Krylov nonlinearity level. At each time step, the exact wetted area of the ship surface under the wave profile was calculated and fed in the time-domain motion and load equations while the diffraction and radiation forces were kept as linear. The present program achieved good agreement with the non-linear PRETTI model results both for the barge and S175 container geometries at zero and forward speed conditions in small amplitude waves. Moreover, the S175 container ship results are compared with the available experimental data and agreed well with the experimental results in forward speed case. It has been observed that PRETTI code is over-estimating motion and load responses especially around the resonant frequency due to the surge motion influence in the memory forces evaluations. In the Froude-Krylov nonlinear level predictions, it has been observed that PRETTI diverges from the experimental results when the wave steepness is higher than 0.08 due to the linear radiation and diffraction forces. Based on the same framework, a more advanced nonlinear time-domain panel code (LARes L3) was developed in order to investigate the effects of quasi-non-linear diffraction and radiation forces in large amplitude ship simulations. A new mesh generator was introduced in order to cut and correct the original panels under the still water level in the updated position of the ship after displacements and rotations. The quasi-non-linear diffraction and radiation forces were calculated at the pre-defined position cases and stored in a database. In order to lower the computational cost multi-dimensional integration and interpolation codes were generated. The S-175 containership was tested in 120 different position cases and resulting hydrodynamic coefficients and forces were stored in the database. The results of the LARes L3 model were compared with the available experimental data using the S-175 containership in forward speed. The computed motion responses showed a good agreement with the experimental data. Moreover, three of the developed models are compared with the experiments and their performances were investigated with respect to the increasing wave slope. In addition to that, the effect of the wave length and ship speed in large amplitude waves are investigated in detail. Non-linear behaviors of the codes were compared with the experimental results which showed a good agreement. Finally, the Vertical Shear Force (VSF) and Vertical Bending Moment (VBM) responses were investigated in large amplitude motions. It was observed that, in the validation section, numerical model peak amplitudes showed well agreement with the experimental results, but they were observed to be shifted to the higher frequencies compared to the experimental results. The reason for that was attributed to the longitudinal mass distribution on the ship in the experimental setup which had not been provided in detail in the published experimental results.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309065372
Category : Science
Languages : en
Pages : 1039
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The Twenty-Second Symposium on Naval Hydrodynamics was held in Washington, D.C., from August 9-14, 1998. It coincided with the 100th anniversary of the David Taylor Model Basin. This international symposium was organized jointly by the Office of Naval Research (Mechanics and Energy Conversion S&T Division), the National Research Council (Naval Studies Board), and the Naval Surface Warfare Center, Carderock Division (David Taylor Model Basin). This biennial symposium promotes the technical exchange of naval research developments of common interest to all the countries of the world. The forum encourages both formal and informal discussion of the presented papers, and the occasion provides an opportunity for direct communication between international peers.
Author: Shukui Liu
Publisher: LAP Lambert Academic Publishing
ISBN: 9783848498093
Category :
Languages : de
Pages : 156
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The reliable prediction of the seakeeping behavior of ships in real seas is a demanding task for naval architects and of great interest to ship owners/operators, as it affects both the design and operation of ships. In this work, a set of methods, namely, a time domain transient Green function solver, alternatively a time domain hybrid solver for zero speed problems and the adopted hybrid solver for nonzero forward speed problem, are developed to study the seakeeping behavior of ships and floating structures in waves. Validation cases cover both simple mathematical geometries and practical ship hulls, either without or with forward speed. Obtained results include radiation/diffraction forces, wave making resistance, motion simulation and added resistance (drift force). It is proved that by properly selecting a solver the developed package is capable of simulating large amplitude motions of ships or floating structures in waves thus it can serve as an advanced tool for the assessment of ship design and operation. This work is expected to offer researchers in similar field a state of art review of the problem and certain amount of inspiration in terms of numerical implementation.
Author: Jean O. DeKat
Publisher:
ISBN:
Category :
Languages : en
Pages : 319
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 341
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An analytical and experimental study of ship motions and capsizing in extreme seas has been conducted. The analysis of linear and quasi-linear one-dimensional roll models has revealed motion anomalies not apparent from the usual linearized ship motion theory. Extensive tests have been conducted using two radio-controlled models in the wind generated seas of San Francisco Bay. Directional spectra were computed, using a variety of techniques, from the wave measurements by an array of wave gages. Comparisons of the experimentally determined motions and a linear strip theory prediction are presented. A time domain numerical simulation program for motions and capsizing has been used to investigate motions in a variety of wave group configurations. The results show good agreement with observed capsizing phenomena and have revealed a number of important characteristics associated with large geometry changes in waves.
Author: B. V. Korvin-Kroukovsky
Publisher:
ISBN:
Category : Bibliography
Languages : en
Pages : 386
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Author: Tuanjie Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 256
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Author: Boris V. Korvin-Krukovskij
Publisher:
ISBN:
Category :
Languages : en
Pages :
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