On movement control of deformable hull for displacement ship in waves

This paper discusses the optimization of ship heading in given regular waves taking into account the limitations for wave-induced midship bending moment and roll amplitude. External and internal forces in irregular waves are determined as per finite-element method used for motion calculations. This study presents the obtained surfaces of responses for the variables of state depending on wave parameters and design variables. The optimization problem discussed in this study was solved taking the non-linearity of target function and limitation functions into account. the study also formulated and solved an inverse problem, i.e. determination of controlling parameters (heading and speed) so as to obtain optimal propulsion performance in given wave conditions without prejudice to reliability and seakeeping.

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Analysis of Ship Structural Loading in a Seaway

Marine Technology and SNAME News ◽

10.5957/mt1.1972.9.2.173 ◽

1972 ◽

Vol 9 (02) ◽

pp. 173-194

Author(s):

Dan Hoffman

Keyword(s):

Pressure Distribution ◽

Phase Relationship ◽

Bending Moment ◽

Green Water ◽

Detailed Structural Analysis ◽

Transverse Pressure ◽

Structural Loading ◽

Wave Induced

The recent advent of the large tanker and bulk carrier has promoted the requirements for more detailed structural analysis of a ship and the reevaluation of theories for calculating the static, quasistatic and dynamic loads. The paper begins with discussion of the methods available to determine the various types of loads expected, their phase relationship, and ways of superimposing them. It then proceeds to the treatment of sea loads based on theoretical and experimental data, and techniques of determining the ship response in a seaway are discussed. The response to regular waves is reviewed with special reference to the determination of pressure distribution on the hull. Statistical ship response, immediate and cumulative over the life of the ship, is demonstrated in relation to the prediction of long-term bending moment trends, and the distribution of the extremes is discussed. Special loading conditions are described with special emphasis on the transverse pressure distribution, dynamic effects due to motion of liquid cargo in tanks, shipping of green water, wave-induced vibrations, slamming pressures and whipping stresses due to various causes. The paper treats the above subjects in a broad manner and no attempt to illustrate the theory in detail is made.

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Bending Moments and Shear Forces in Ships Sailing in Irregular Waves

Journal of Ship Research ◽

10.5957/jsr.1981.25.4.243 ◽

1981 ◽

Vol 25 (04) ◽

pp. 243-251

Author(s):

J. Juncher Jensen ◽

P. Terndrup Pedersen

Keyword(s):

Linear Part ◽

Vertical Motion ◽

Bending Moment ◽

Irregular Waves ◽

Bending Moments ◽

Shear Forces ◽

Strip Theory ◽

Wave Heights ◽

Exciting Forces ◽

Wave Induced

This paper presents some results concerning the vertical response of two different ships sailing in regular and irregular waves. One ship is a containership with a relatively small block coefficient and with some bow flare while the other ship is a tanker with a large block coefficient. The wave-induced loads are calculated using a second-order strip theory, derived by a perturbational procedure in which the linear part is identical to the usual strip theory. The additional quadratic terms are determined by taking into account the nonlinearities of the exiting waves, the nonvertical sides of the ship, and, finally, the variations of the hydrodynamic forces during the vertical motion of the ship. The flexibility of the hull is also taken into account. The numerical results show that for the containership a substantial increase in bending moments and shear forces is caused by the quadratic terms. The results also show that for both ships the effect of the hull flexibility (springing) is a fair increase of the variance of the wave-induced midship bending moment. For the tanker the springing is due mainly to exciting forces which are linear with respect to wave heights whereas for the containership the nonlinear exciting forces are of importance.

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Experimental Assessment of Form Based Approach for Predicting Extreme Value Distribution of Hull Girder Bending Moment in a Ship

Volume 3: Structures, Safety, and Reliability ◽

10.1115/omae2019-95389 ◽

2019 ◽

Author(s):

Tomoki Takami ◽

Yusuke Komoriyama ◽

Takahiro Ando ◽

Kazuhiro Iijima

Keyword(s):

Estimation Method ◽

Bending Moment ◽

Extreme Value Distribution ◽

Irregular Waves ◽

Extreme Wave ◽

Scaled Model ◽

Element Analysis ◽

Hull Girder ◽

Reliability Method ◽

Wave Induced

Abstract This paper describes a series of towing tank tests using a scaled model of a recent container ship for validating the First Order Reliability Method (FORM) based approach to predict the maximum response. The FORM based approach is adopted in conjunction with the nonlinear strip method as an estimation method for the most probable wave episodes (MPWEs) leading to the given extreme wave-induced vertical bending moments (VBMs). Tank tests under the pre-determined MPWEs are conducted to evaluate the extreme wave-induced VBMs. Numerical simulations based on the coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) are also conducted and are compared with the test results under the MPWEs. Furthermore, to estimate the extreme VBM statistics, tank tests under random irregular waves are conducted. A series of validations of the probability of exceedances (PoEs) of the VBM evaluated from the FORM based approach is carried out. The effect of hydroelastic (whipping) vibrations on the extreme VBM statistics are finally discussed.

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CFD Analysis of Deck Impact in Irregular Waves: Wave Representation by Transient Wave Groups

Volume 7: CFD and VIV; Offshore Geotechnics ◽

10.1115/omae2011-49418 ◽

2011 ◽

Cited By ~ 1

Author(s):

O̸ystein Lande ◽

Thomas B. Johannessen

Keyword(s):

Wave Field ◽

Irregular Waves ◽

Computational Domain ◽

Cfd Analysis ◽

Wave Group ◽

Regular Waves ◽

Transient Wave ◽

Wave Groups ◽

Wave Induced ◽

Random Background

Analysis of wave structure interaction problems are increasingly handled by employing CFD methods such as the well known Volume-of-Fluid (VoF) method. In particular for the problem of deck impact on fixed structures with slender substructures, CFD methods have been used extensively in the last few years. For this case, the initial conditions have usually been treated as regular waves in an undisturbed wave field which may be given accurately as input. As CFD analyses become more widely available and are used for more complex problems it is also necessary to consider the problem of irregular waves in a CFD context. Irregular waves provide a closer description of the sea surface than regular waves and are also the chief source of statistical variability in the wave induced loading level. In general, it is not feasible to run a long simulation of an irregular seastate in a CFD analysis today since this would require very long simulation times and also a very large computational domain and sophisticated absorbing boundary conditions to avoid build-up of reflections in the domain. The present paper is concerned with the use of a single transient wave group to represent a large event in an irregular wave group. It is well known that the autocovariance function of the wave spectrum is proportional to the mean shape of a large wave in a Gaussian wave field. The transient nature of such a wave ensures that a relatively small wave is generated at the upwave boundary and dissipated at the downwave boundary compared with the wave in the centre of the domain. Furthermore, a transient wave may be embedded in a random background if it is believed that the random background is important for the load level. The present paper describes the method of generating transient wave groups in a CFD analysis of wave in deck impact. The evolution of transient wave groups is first studied and compared with experimental measurements in order to verify that nonlinear transient waves can be calculated accurately using the present CFD code. Vertical wave induced loads on a large deck is then investigated for different undisturbed wave velocities and deck inundations.

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Numerical Investigation of Hydrodynamic Performance of a Light Buoy with Different Mooring Configurations in Regular Waves

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4052477 ◽

2021 ◽

pp. 1-26

Author(s):

Xin Li ◽

Yimei Chen ◽

Lilei Mao ◽

Huiyu Xia

Keyword(s):

Experimental Data ◽

Yangtze River ◽

Coupled Model ◽

Coupling Model ◽

Numerical Approach ◽

Hydrodynamic Performance ◽

Irregular Waves ◽

Regular Waves ◽

Induced Motion ◽

Wave Induced

Abstract The single-moored light buoys employed in the lower reaches of the Yangtze River play an important role in indicating ship navigation and ensuring safety. To clarify the interaction between waves and floating buoys moored to the riverbed, this paper develops a numerical approach to investigate the wave-induced motion performance of a light buoy and reveal the effects of different mooring configurations to extend its service life. A new open-source SPH based numerical model named DualSPHysics coupled with MoorDyn is implemented. This coupled model is validated by simulating the motion of a moored rectangle buoy in regular waves, and compared with experimental data and the numerical results of REEF3D code, a new mesh-based CFD model. The validation results show that the coupled model reproduces experimental data well and has a smaller deviation in comparison with REEF3D. Then the coupling model is applied to simulate the hydrodynamic performance of the real-size light buoy employed in Yangtze River and investigate effects of encounter angle between wave propagation direction and mooring chain. The results demonstrate the capability of this coupled mooring model to simulate the motion of a moored buoy in regular waves, and this numerical approach will be extended to simulate the light buoy in more complex environments such as irregular waves, flow or extreme weather in further work.

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Improved Generalized Procedure for Determining Critical State of a Thin-Walled Beam Under Combined Symmetric Loads

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455419500986 ◽

2019 ◽

Vol 19 (08) ◽

pp. 1950098 ◽

Cited By ~ 1

Author(s):

Phung Van Binh ◽

Nguyen Viet Duc ◽

Prokopov Vladimir Sergeevich ◽

Dang Hoang Minh

Keyword(s):

Bending Moment ◽

Complex Loading ◽

Computational Procedure ◽

Beam Length ◽

Concentrated Load ◽

Internal Forces ◽

Thin Walled ◽

The Stability ◽

External Loads

This paper presents an improved generalized procedure for dealing with the stability of thin-walled beams under combined symmetric loads based on the energy method. The differential equations for the case of complex loading conditions were developed using an axis transformation matrix. The work caused by external loads was related to the work of internal forces to simplify the computational procedure. The thin-walled beam subjected to axial force [Formula: see text], bending moment [Formula: see text] at both ends, and concentrated load [Formula: see text] at midspan was studied. The case of a concentrated load [Formula: see text] replaced by a distributed load [Formula: see text] over partial beam length was also examined. The stability region boundary of the beam was derived by two approaches: one was to estimate an approximate angle of twist prior to determination of the deflection and the other was to do it in the reverse way. Numerical results reveal that the first approach yields less error than the second; however, the outcome obtained by the former was more cumbersome than the latter. Above all, both approaches provided feasible results and are useful for further applications dealing with the stability analysis of thin-walled beams.

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Random Wave-Induced Momentary Liquefaction around Rubble Mound Breakwaters with Submerged Berms

Journal of Marine Science and Engineering ◽

10.3390/jmse8050338 ◽

2020 ◽

Vol 8 (5) ◽

pp. 338

Author(s):

Daniele Celli ◽

Yuzhu Li ◽

Muk Chen Ong ◽

Marcello Di Risio

Keyword(s):

Irregular Waves ◽

Random Wave ◽

Random Waves ◽

Regular Waves ◽

Peak Period ◽

Soil Response ◽

Minimum Number ◽

Rubble Mound ◽

Wave Induced ◽

Rubble Mound Breakwaters

The effects of submerged berms in attenuating the momentary liquefaction beneath rubble mound breakwaters under regular waves were investigated in a recent study. The present work aims to investigate the momentary liquefaction probabilities around and beneath breakwaters with submerged berms under random waves. The interaction between waves and breakwaters with submerged berms has been simulated through a phase-resolving numerical model. The soil response to the seabed pressure induced by random waves has been investigated using a poro-elastic soil solver. For three different breakwater configurations, the liquefaction depths under random wave conditions have been compared with those cases under representative regular waves. In the present study, the offshore spectral wave height ( H m 0 ) and the peak period ( T p ) of irregular waves are used as representative regular wave parameters. Results reveal the importance of considering random waves for a safe estimation of the momentary liquefaction probability. Indication about the minimum number of random waves, which is required to properly catch the liquefaction occurrences, has been also addressed.

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A Literature Review of Wave-Induced Heave Motion of Floating Structures

Journal of Architectural Research and Development ◽

10.26689/jard.v2i1.247 ◽

2018 ◽

Vol 2 (1) ◽

Author(s):

Jia qi Xue

Keyword(s):

Wave Theory ◽

Body Motion ◽

Irregular Waves ◽

Floating Body ◽

Superposition Method ◽

Regular Waves ◽

Floating Structure ◽

Floating Structures ◽

Heave Motion ◽

Wave Induced

This paper provides comprehensive review on heave motion of rigid floating structure due to wave impacts. To specify and explain the structure response, this review firstly provides a brief introduction on ocean sea wave theory, floating structure motion interpretation. Then the floating body motion in regular waves was demonstrated using a superposition method of the oscillated motion in still water and the restrained motion inÂ waves. Meanwhile, added mass and damping coefficient, these two frequency-dependent terms are brought into discussion to generate the motion response with given wave amplitude, which is known for response amplitude operator( RAO). Based on the study in regular waves, RAO of floating structure in irregular waves is introduced while no longer in time domain but in frequency domain. The whole review covers the literatures from the early 1980s up to nowadays, based on the review, it is recommended that more experimental work regarding to frequency characteristic and relative response of larger floating body should be carried out to improve the accuracy of this method.

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