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1
Lian-zhou, Wang, Guo Chun-yu, Wan Lei et Su Yu-min. « Numerical Analysis of Propeller During Heave Motion Near a Free Surface ». Marine Technology Society Journal 51, no 1 (1 janvier 2017) : 40–51. http://dx.doi.org/10.4031/mtsj.51.1.5.
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AbstractThe interaction between the free surface and the propeller during heave motion near the free surface was analyzed numerically using the Reynolds-Averaged Navier-Stokes (RANS) method. The coupling effect between the rotation and heave motions of the propeller was modeled using a motion equation developed in this study; the heave motion was simplified as a periodic motion based on the sinusoidal motion law; and the transfer of numerical values for unsteady flow fields was implemented using overset grid technology. A comparative analysis of the unsteady thrust coefficient and torque coefficient under different advance coefficient conditions was conducted, and the air ingestion phenomenon of the propeller was analyzed. The research highlighted the interaction between the coupled heave and rotation motions of the propeller and the free surface. The results showed that, when the advance coefficient was low, the hydrodynamic performance of the propeller during heave motion near a free surface was strongly influenced by the free surface and that a remarkable interaction existed between the propeller and the free surface. As the advance coefficient increased, the interaction between the propeller and the free surface weakened. The air ingestion that the propeller exerts upon the free surface during heave motion is a complex coupled superposition process. This phenomenon is correlated to the motion state and working time of the propeller, as well as the distance between the propeller and the free surface.
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Tabeshpour, Mohammad Reza, et Reza Hedayatpour. « Analytical investigation of nonlinear heave-coupled response of tension leg platform ». Proceedings of the Institution of Mechanical Engineers, Part M : Journal of Engineering for the Maritime Environment 233, no 3 (7 juin 2018) : 699–713. http://dx.doi.org/10.1177/1475090218776430.
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Having deep view in structural response of tension leg platform is important issue not only for response analysis but also for engineering design. Coupling between surge and heave motions of tension leg platform is such a problem. Here, tension leg platform motions are considered only in surge and heave degrees of freedom without pitch effect. The coupled term of heave is a nonlinear differential equation. Because the focus of this article is on this term, therefore, Duffing equation of motion in the surge direction is linearized. The wave forces are calculated using Airy’s wave theory and Morison’s equation, ignoring the diffraction effects. Current force also can be very important in dynamic analysis of tension leg platform. Because it affects the term of heave that is coupled with surge. It is shown that the effect of surge motion coupling on heave motion is very important in large displacement of surge motion in many sea states. The main result is that the coupling effects appeared in some frequencies such as heave and surge frequency, twice the frequency of wave, twice the natural surge frequency, and summation and difference of frequency of wave and surge frequency.
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FITRIADHY, AHMAD, et AMIRA ADAM. « CFD ANALYSIS ON VERTICAL MOTION OF A FULL-SCALE FLOATING JETTY ». Journal of Sustainability Science and Management 15, no 6 (30 août 2020) : 100–110. http://dx.doi.org/10.46754/jssm.2020.08.009.
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A floating jetty often experiences several vertical motions i.e., heave and pitch motion responses due to harsh environmental condition. This inherently makes discomfort to everyone during berthing on a floating; and even it potentially leads to loss of life due to falling down into the sea. A preliminary analysis using Computational Fluid Dynamics (CFD) simulation is necessary to be conducted to ensure user’s safety. The CFD analysis focused on the interaction between wave motions and the floating jetty and its effects on the vertical motions. The vertical motions of floating jetty were quantified by the Response Amplitude Operators (RAO). Several effects due to variation of wavelength (λ/L) have been studied. The CFD results revealed that the lower wavelength (λ/L<2.25) resulted in the increase of the heave and pitch motion amplitudes proportionally. However, the subsequent increase of wavelength (2.25>λ/L) has given results to less heave and pitch motion amplitudes. In general, it is shown that the vertical motion characteristics of the floating jetty predominantly depend on wave properties.
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ZIKRY, SYAFIQ, et FITRIADHY. « SEAKEEPING PERFORMANCE OF A HYDROFOIL IN WAVES USING CFD APPROACH ». Universiti Malaysia Terengganu Journal of Undergraduate Research 3, no 3 (31 juillet 2021) : 167–76. http://dx.doi.org/10.46754/umtjur.v3i3.228.
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Hydrofoil usually experiences high resistance and excessive vertical motions (heave and pitch) that may affect the passenger’s comfort due to the harsh environmental condition. Therefore, it is necessary to investigate seakeeping performance of a hydrofoil ship in waves due to the presence of a complex hydrodynamic phenomenon. To achieve this objective, an analysis of Computational Fluid Dynamic (CFD) approach on a hydrofoil ship motion is proposed. Several parameters such as Froude Number and foil angle of attack have been taken into account. The results revealed that the subsequent increase of Froude Number was inversely proportional to the heave and pitch motions. Inherently, these have led to an upgrade of hydrofoil seakeeping performances presented in the form of high Response Amplitude Operators (RAO). Furthermore, the increasing angle of the foil bow was proportional to the heave motion while for the foil stern, 7.5o showed lower heave motion, then followed by 5o and 10o respectively. For the pitch motion, the increase of foil bow was lower at 5o then followed by 10o and 7.5o. The increase of the foil stern was proportional to the pitch motion experiences by a hydrofoil. In general, this CFD simulation is very beneficial to ensure operational effectiveness of hydrofoil design in high sea states with respect to the aforementioned design parameter.
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Sclavounos, Paul D., et Henning Borgen. « Seakeeping Analysis of a High-Speed Monohull With a Motion-Control Bow Hydrofoil ». Journal of Ship Research 48, no 02 (1 juin 2004) : 77–117. http://dx.doi.org/10.5957/jsr.2004.48.2.77.
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The seakeeping performance is studied of a foil-assisted high-speed monohull vessel using a state-of-the-art three-dimensional Rankine panel method. The vessel is equipped with a bow hydrofoil acting as a passive heave and pitch motion-control device in waves. The formulation of the seakeeping of ships equipped with lifting appendages is developed, and the mechanisms responsible for the reduction of the heave and pitch motions of high- speed vessels equipped with hydrofoils are studied. The sensitivity of the heave and pitch motions on the longitudinal position of the hydrofoil is studied. It is found that the most efficient location for the hydrofoil is at the ship bow leading to a 50% reduction of the root mean square values of the heave and pitch motions in a Joint North Sea Wave Project (JONSWAP) spectrum. Several extensions of the analysis of the present paper are discussed. They include the reduction of the roll motion of high-speed vessels, the design of optimal active motion-control mechanisms, and the coupling of the hull form and lifting appendage design for high-speed monohull vessels.
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Sun, Han-Bing, Shu-Qi Yang, Yang-Fan Xu et Jia-Feng Xiao. « Prediction of the Pitch and Heave Motions in Regular Waves of the DTMB 5415 Ship Using CFD and MMG ». Journal of Marine Science and Engineering 10, no 10 (22 septembre 2022) : 1358. http://dx.doi.org/10.3390/jmse10101358.
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According to the requirement of high-performance development of modern ships, it is necessary to quickly and accurately predict the maneuverability of ships under wave conditions. In this paper, based on the CFD (Computational Fluid Dynamics) method in the commercial software STAR-CCM+, the numerical simulation of roll decay motion, pure heel motion, pure heave motion, and pure pitch motion of ship model 5415 is carried out. The relevant hydrodynamic derivatives are obtained, and the results are in good agreement with the experimental values. The equations of motion related to the heave and pitch motions are established according to the MMG (Maneuvering Motion Equation Research Group) model. Then, based on the above dynamic equations, the wave force module is added to successfully simulate and predict the pitch and heave responses of the ship under regular wave conditions, and it is concluded that the simulation model for rapid predic-tion is also applicable under waves.
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Ciba, Ewelina. « Heave Motion of a Vertical Cylinder with Heave Plates ». Polish Maritime Research 28, no 1 (1 mars 2021) : 42–47. http://dx.doi.org/10.2478/pomr-2021-0004.
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Abstract The shape of a vertical cylinder resembles the classic form of a spar platform. Spar platforms are floating platforms that are successfully used in waters of great depths and have several advantages that mean they are readily used in the oil industry. Many of these advantages are also relevant to their application for offshore wind turbines, which is currently being considered. In the hydrodynamic analysis of spar platforms, the determination of their hydrodynamic coefficients plays an important role. They can be determined based on the free decay test. The study presents a method for determining the hydrodynamic coefficients of an object based on the free decay test. The results of free oscillation calculations with the help of numerical fluid mechanics tools are presented and compared with the results of the experiment and analytical solution. The application of determined coefficients and their significance for floating platforms are discussed. The influence of change in the form of an additional damping element on the behaviour of spar structures is shown.
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Dao, Nguyen Van. « Nonlinear model simulation of ship motion ». Vietnam Journal of Mechanics 14, no 2 (31 mars 1992) : 7–12. http://dx.doi.org/10.15625/0866-7136/10227.
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Nonlinear model simulation of coupling between heave-roll and pitch roll ship motions is considered by means of the asymptotic method of nonlinear mechanics. The purely vertical motion and vertical-angular motion and their stability are studied.
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Jiang, Yichen, Guanqing Hu, Zhi Zong, Li Zou et Guoqing Jin. « Influence of an Integral Heave Plate on the Dynamic Response of Floating Offshore Wind Turbine Under Operational and Storm Conditions ». Energies 13, no 22 (22 novembre 2020) : 6122. http://dx.doi.org/10.3390/en13226122.
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The hydrodynamic performance of the floating foundation for offshore wind turbines is essential to its stability and energy harvesting. A semi-submersible platform with an integral heave plate is proposed in order to reduce the vertical motion responses. In this study, we compare the heave, pitch, and roll free decay motions of the new platform with a WindFloat-type platform based on Reynolds-Averaged Navier-Stokes simulations. The differences of the linear and quadratic damping properties between these platforms are revealed. Then, a FAST (Fatigue, Aerodynamics, Structures, and Turbulence) model with the consideration of fluid viscosity effects is set up to investigate the performance of the new platform under storm and operational conditions. The time-domain responses, motion spectra, and the mooring-tension statistics of these two platforms are evaluated. It is found that the integral heave plate can increase the viscous hydrodynamic damping, significantly decrease the heave and pitch motion responses, and increase the safety of the mooring cables, especially for the storm condition.
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Karambas, Theofanis, et Eva Loukogeorgaki. « A Boussinesq-Type Model for Nonlinear Wave-Heaving Cylinder Interaction ». Energies 15, no 2 (10 janvier 2022) : 469. http://dx.doi.org/10.3390/en15020469.
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In the present work, a Boussinesq-type numerical model is developed for the simulation of nonlinear wave-heaving cylinder interaction. The wave model is able to describe the propagation of fully dispersive and weakly nonlinear waves over any finite water depth. The wave-cylinder interaction is taken into account by solving simultaneously an elliptic equation that determines the pressure exerted by the fluid on the floating body. The heave motion for the partially immersed floating cylinder under the action of waves is obtained by solving numerically the body’s equation of motion in the z direction based on Newton’s law. The developed model is applied for the case of a fixed and a free-floating circular cylinder under the action of regular waves, as well as for a free-floating cylinder undergoing a forced motion in heave. Results (heave and surge exciting forces, heave motions, and wave elevation) are compared with those obtained using a frequency domain numerical model, which is based on the boundary integral equation method.
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Shen, Wen Jun, You Gang Tang et Li Qin Liu. « Nonlinear Analysis of Stochastic Heave Motion for Truss Spar ». Applied Mechanics and Materials 548-549 (avril 2014) : 531–36. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.531.
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Applying the Path Integral Solution Method, the stochastic heave motion of Truss Spar platform was studied in this paper. Taking a platform for example, probability density function of stochastic heave motion amplitude was calculated under the conditions of different wave excitations. The results show that, the changing process of probability density function in the time domain has an obvious periodicity. As the increasing of external excitation, the heave motion amplitude and speed both increases. Meanwhile, as the increasing of excitation amplitude, the probability density function of heave motion has a more pronounced periodicity.
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Tao, Longbin, et Shunqing Cai. « Heave motion suppression of a Spar with a heave plate ». Ocean Engineering 31, no 5-6 (avril 2004) : 669–92. http://dx.doi.org/10.1016/j.oceaneng.2003.05.005.
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Hwang, Sung Gu, Gwi Nam Kim, Yong Gil Jung et Sun Chul Huh. « Safety Assessment of Heave Compensator Using Multi-Body Dynamics ». Applied Mechanics and Materials 764-765 (mai 2015) : 364–68. http://dx.doi.org/10.4028/www.scientific.net/amm.764-765.364.
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Heave Compensation system minimizes vessel heave motion during drilling operation of drillship. Heave compensator plays a role as damping form heave motion of drillship such as principle spring of car suspension system. The load transfers on the parts of heave compensator. Stress and deformation of all parts is evaluated to diagnose the stability of the compensator. This study makes a decision on the safety of structure by ANSYS 12.0v workbench.
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Ni, Shengke, Zhengjiang Liu, Yao Cai et Teng Zhang. « A Practical Approach to Numerically Predicting a Maneuvering Vessel in Waves Oriented to Maritime Simulator ». Mathematical Problems in Engineering 2020 (26 octobre 2020) : 1–11. http://dx.doi.org/10.1155/2020/8361951.
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To improve the behavioral realism of maritime simulator, the mathematical model of ship heave and pitch motion in regular waves is proposed. To avoid the influence of irregular frequency by two-dimensional Frank source and sink distribution method, the multiparameter conformal mapping method was adopted to solve the hydrodynamic problem of ship’s transverse sections, and then the integration of the hydrodynamic coefficients and the wave exciting forces for the whole ship hull was obtained using the Salvesen–Tuck–Faltinsen (STF) strip method. The Abkowitz model was used for the horizontal maneuverability motion equations, and the ship heave and pitch motion mathematical model in regular waves can be built considering the maneuvering factors. To verify the credibility and applicability of the improved model, the Mariner vessel with a Froude number of 0.2 was taken as the simulation case; when Mariner vessel sails in head waves, the maximum relative error between the calculated results and the experimental results is 23.6% for amplitude response operators of ship heave and pitch motion, and the calculated results and the experimental results have the same trend. When turning maneuvers in regular waves are carried out, the time history of ship pitch and pitch motions in regular waves does not show the sinusoidal periodic change any more, but the time history of heave and pitch motion still possesses periodic change to some extent, at which the period is about the time required for the turning motion to finish a circle. When turning maneuvers are carried out for 3000 seconds, the time required for computer operation is about 487.6 s, and the real-time requirements of maritime simulator are satisfied. Thus, the mathematical model of ship heave and pitch motion established in this paper can be effectively applied to the maritime simulator.
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Li, Zhou, Liu et Wang. « Numerical Analysis of Influence of the Hull Couple Motion on the Propeller Exciting Force Characteristics ». Journal of Marine Science and Engineering 7, no 10 (23 septembre 2019) : 330. http://dx.doi.org/10.3390/jmse7100330.
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The numerical calculation was performed for the KRISO Container Ship (KCS) hull-propeller-rudder system with different freedom hull motion by employing the Reynolds-Averaged Navier-Stokes (RANS) method and adopting the overset grid. Firstly, the numerical simulation of hydrodynamics for a bare hull with the heave and pitch motion is carried out. The results show that the space non-uniformity of a nominal wake in the disk plane with motion is comparable to the case without motion. However, the time non-uniformity increases sharply and it has a significant positive relationship with the motion amplitude. Then, the propeller exciting force is calculated in the case including single heave, single pitch and their couple motion. It was found that both the ship and propeller hydrodynamic performance deteriorated dramatically due to the hull motion. Furthermore, the spectrum peak at the motion frequency is dominant in all the peak values and the larger the amplitude is, the higher the motion frequency peak is expected to be. For the propeller bearing force, the effect of the different hull motions appears as linear superimposition. However, the superimposition of different hull motions enlarges the propeller-induced fluctuating pressure in a single motion.
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Li, Yajie, et Yun Long. « Numerical Study on Wave Radiation by a Barge with Large Amplitudes and Frequencies ». Journal of Marine Science and Engineering 8, no 12 (19 décembre 2020) : 1034. http://dx.doi.org/10.3390/jmse8121034.
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A two-dimensional boundary element method is used to study the hydrodynamics of a single barge with prescribed motions of large amplitudes and high frequencies. The wave radiation problem is solved in the time domain based on the fully nonlinear potential flow theory. For numerical simulations, special treatments like plunging wave cutting and remeshing approaches are presented in detail. The numerical schemes are verified through comparing with analytical results. Both the generated outgoing wave amplitudes and hydrodynamic coefficients can be calculated with sufficient accuracy. Then, we focus on large heave, sway and roll motions to investigate the nonlinear effects on hydrodynamic forces, respectively. In particular, the heave motion with two frequencies is also simulated to study the interactions between results at different frequencies. It is interesting to see the sum and difference frequency components and the envelopes in time histories as a result. For forces caused by forced sway or roll motions, there are only even-order harmonics for vertical forces and only odd-order harmonics for horizontal forces. Finally, a single body with combined sway, heave and roll motion is studied to examine the interactions between motion modes.
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Guo, Y., Y. P. Jing, M. Jiang et B. W. Luo. « Disturbance Observer Based Heave Compensation Control for Benthic Coring Drill ». Open Mechanical Engineering Journal 7, no 1 (27 décembre 2013) : 129–35. http://dx.doi.org/10.2174/1874155x01307010129.
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Severe environment in deep ocean affects operating reliability and security of coring drill. Adopting heave motion signal measured by accelerometer to confirm heave compensation of coring drill, the compensation control method is proposed using disturbance observer to restrain the disturbance. Then, the disturbance observer is designed. The heave motion simulation for coring drill is done with this control method, and the results show that the heave motion compensation control of coring drill using disturbance observer avoids the disturbance with high tracking quality, and provides high reliability and security to coring drill operating.
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Yim, Solomon C. S., Tongchate Nakhata, Warren A. Bartel et Erick T. Huang. « Coupled Nonlinear Barge Motions, Part I : Deterministic Models Development, Identification and Calibration ». Journal of Offshore Mechanics and Arctic Engineering 127, no 1 (1 février 2005) : 1–10. http://dx.doi.org/10.1115/1.1854700.
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This paper focuses on the development of optimal deterministic, nonlinearly coupled barge motion models, identification of their system parameters, and calibration of their prediction capability using experimental results. The ultimate objective is to develop accurate yet sufficiently low degree-of-freedom stochastic models suitable for efficient probabilistic stability and reliability analyses of US Naval barges for preliminary design and operation guideline development (see Part II). First a three-degree-of-freedom (3DOF) fully coupled roll-heave-sway model, which features realistic and practical high-degree polynomial approximations of rigid body motion relations, hydrostatic and hydrodynamic force-moment specifically suitable for barges, is examined. The hydrostatic force-moment relationship includes effects of the barge’s sharp edge and combined roll-heave states, and the hydrodynamic terms are in a “Morison” type quadratic form. System parameters of the 3DOF model are identified using physical model test results from several regular wave cases. The predictive capability of the model is then calibrated using results from a random wave test case. Recognizing the negligible sway influence on coupled roll and heave motions and overall barge stability, and in an attempt to reduce anticipated stochastic computational efforts in stability analysis, a two-degree-of-freedom (2DOF) roll-heave model is derived by uncoupling sway from the roll-heave governing equations of motion. Time domain simulations are conducted using the 3DOF roll-heave-sway and the 2DOF roll-heave models for regular and random wave cases to validate the model assumptions and to assess their (numerical) prediction capabilities.
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Fitriadhy, Ahmad, Nur Adlina Aldin, Nurul Aqilah Mansor et Nur Aqilah Hanis Zalizan. « Heave and Pitch Motion Performances of a Ship Towing System Incorporated with Symmetrical Bridle Towline Model ». EPI International Journal of Engineering 2, no 1 (27 juin 2019) : 28–33. http://dx.doi.org/10.25042/epi-ije.022019.06.
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An investigation on vertical motion characteristics of a ship towing system incorporated with symmetrical bridle towline configuration set a real challenge for the naval architect engineer. This paper presents a Computational Fluid Dynamic (CFD) approach to analyse heave and pitch motion performances in waves. Several towing parameters such as various towline length and towing’s velocity have been taken into account. Here, 1B (barge) is employed in the simulation; and designated as a towed ship. The results revealed that the subsequent increase of the towline lengths has been basically proportional with the increase of her heave motion; while inversely decrease in pitch motions. In addition, the effect of the extending towline length = 1.0 to 3.0 resulted in insignificant effect to the towline tension. However, the increase of the towing’s velocity from 0.509 m/s to 0.728 m/s has led to significantly increase her heave motion and the towline tension by 40.46% and 24%, respectively; meanwhile, the pitch motion barge has sufficiently decreased by 35.94%. This simulation has been beneficial for the towing operator to ensure a higher level of the safety navigation of ship towing system.
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Kirk, C. L. « Resonant heave motion of semisubmersible vessels ». Ocean Engineering 12, no 2 (janvier 1985) : 177–84. http://dx.doi.org/10.1016/0029-8018(85)90080-0.
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Zhang, Jie, Ying Zeng, Yougang Tang, Wenyun Guo et Zhenkui Wang. « Numerical and Experimental Research on the Effect of Platform Heave Motion on Vortex-Induced Vibration of Deep Sea Top-Tensioned Riser ». Shock and Vibration 2021 (16 mars 2021) : 1–13. http://dx.doi.org/10.1155/2021/8866051.
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The prediction and control of vortex-induced vibration (VIV) is one of the key problems for riser design. The effect of platform heave motion on VIV of deep sea top-tensioned riser (TTR) is presented by means of numerical simulation and experiment in this research. First, the heave motion was modeled as a parametric excitation, and the governing equation of VIV of riser considering the parametric excitation was established. Then, the dynamic response of TTR was calculated numerically by the finite difference method based on the Van der Pol wake-oscillator model. Finally, a validation experiment was carried out at the towing tank of Tianjin university. The results show that the VIV response at the bottom of riser is significantly increased due to the platform heave motion, especially in the situation of low current velocity. The larger amplitude and the higher frequency of the platform heave motion with the greater influence are generated on VIV of TTR. In particular, the value of 0.5 times, 1 time, or other multiples of the platform heave frequency will be included in the vibration frequency component of TTR when the platform heave amplitude is large and the frequency is high.
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Jamal, A. Sulisetyono et W. D. Aryawan. « Direct Measurement of Motion on Fast Ferries ». IOP Conference Series : Earth and Environmental Science 1081, no 1 (1 septembre 2022) : 012036. http://dx.doi.org/10.1088/1755-1315/1081/1/012036.
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Abstract This paper describes a new identification method for the fast ferry motions by using the direct measurements on the ship’s board. The inertial sensor type of the Analog Devices (ADIS) 16364 is selected as a as suitable instrument to measure accelerations and velocity of the ship motions namely heave, pitch, and roll in time domain. Furthermore, the ship motion responses are transferred as the energy spectral density in frequency domain which are identified using the Fast Fourier Transform (FFT) method. For the case study, the measurement equipment was placed on the navigation room of MV. Dumai Line 12 recording in 15 minutes within ship voyage from Bengkalis to Batam in September 2021. Finally, the natural frequencies of heave, pitch, and roll motions are identified about 0.568 rad/s, 0.117 rad/s, and 0.227 rad/s, respectively.
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Liu, Kun, Haizhi Liang, Jingpin Ou, Jiawei Ye et Dongjiao Wang. « Experimental Investigation of the Performance of a Tuned Heave Plate Energy Harvesting System for a Semi-Submersible Platform ». Journal of Marine Science and Engineering 10, no 1 (1 janvier 2022) : 45. http://dx.doi.org/10.3390/jmse10010045.
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Heave plates are widely used for improving the sea keeping performance of ocean structures. In this paper, a novel tuned heave plate energy harvesting system (THPEH) is presented for the motion suppression and energy harvesting of a semi-submersible platform. The heave plates are connected to the platform though a power take-off system (PTO) and spring supports. The performance of the THPEH was investigated through forced oscillation tests of a 1:20 scale model. Firstly, the hydrodynamic parameters of the heave plate were experimentally studied under different excitation motion conditions, and a force model of the power take-off system was also established through a calibration test. Then, the motion performance, control performance, and energy harvesting performance of the THPEH subsystem were systematically studied. The effects of the tuned period and PTO damping on the performance of the THPEH were analyzed. Finally, a comparison between the conventional fixed heave plate system and THPEH was carried out. The results show that a properly designed THPEH could consume up to 2.5 times the energy from the platform motion compared to the fixed heave plate system, and up to 80% of the consumed energy could be captured by the PTO system. This indicates that the THPEH could significantly reduce the motion of the platform and simultaneously provide considerable renewable energy to the platform.
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Li, Jiangfan, Liang Li et Xiaofei Wen. « A novel method of estimating ship heave motion based on dual inertial measurement units ». Journal of Physics : Conference Series 2183, no 1 (1 janvier 2022) : 012002. http://dx.doi.org/10.1088/1742-6596/2183/1/012002.
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Abstract In order to estimate the ship heave displacement information in real time and accurately, combined with the ship heave motion model, a dual inertial measurement units (IMU) ship heave displacement estimation method is proposed, the corresponding observer is established, and the heave information of the two Imus is fused. The simulation results show that the dual IMU ship heave estimation method has higher accuracy than the single IMU ship heave estimation method.
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Gao, Yue Wen, Chun Li et Xin Cheng. « Performance Research on Tension Leg Platform of Floating Offshore Wind Turbine ». Advanced Materials Research 724-725 (août 2013) : 645–48. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.645.
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Platform structure is the basic guarantee for safety operation of offshore wind turbine. Based on the boundary element method and combined with multi-body dynamics, analyzing motion response and wave force mechanism to the platform structure, and obtained the dynamic response and the wave force change of the platform structures in time domain, last analyzes the motion response and wave force change of tension leg platform in surge, sway and heave also roll, pitch and yaw direction. The results show that the maximum response of sway and the minimum response of surge have the same direction, it is the same with the maximum response of pitch and the minimum response of roll ; Motion responses of heave and yaw change not as acutely as other four directions ; In time-domain variation range, motion response of surge, heave and pitch change acutely, while motion responses of sway, roll and yaw change slightly. Wave force focus mostly in heave and pitch direction. The results is high reference value on offshore tension leg platform structural design and optimization.
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Trslić, Petar, Edin Omerdic, Gerard Dooly et Daniel Toal. « Neuro-Fuzzy Dynamic Position Prediction for Autonomous Work-Class ROV Docking ». Sensors 20, no 3 (27 janvier 2020) : 693. http://dx.doi.org/10.3390/s20030693.
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This paper presents a docking station heave motion prediction method for dynamic remotely operated vehicle (ROV) docking, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS). Due to the limited power onboard the subsea vehicle, high hydrodynamic drag forces, and inertia, work-class ROVs are often unable to match the heave motion of a docking station suspended from a surface vessel. Therefore, the docking relies entirely on the experience of the ROV pilot to estimate heave motion, and on human-in-the-loop ROV control. However, such an approach is not available for autonomous docking. To address this problem, an ANFIS-based method for prediction of a docking station heave motion is proposed and presented. The performance of the network was evaluated on real-world reference trajectories recorded during offshore trials in the North Atlantic Ocean during January 2019. The hardware used during the trials included a work-class ROV with a cage type TMS, deployed using an A-frame launch and recovery system.
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Beck, Robert F., et Stergios Liapis. « Transient Motions of Floating Bodies at Zero Forward Speed ». Journal of Ship Research 31, no 03 (1 septembre 1987) : 164–76. http://dx.doi.org/10.5957/jsr.1987.31.3.164.
Texte intégralRésumé :
Linear, time-domain analysis is used to solve the radiation problem for the forced motion of a floating body at zero forward speed. The velocity potential due to an impulsive velocity (a step change in displacement) is obtained by the solution of a pair of integral equations. The integral equations are solved numerically for bodies of arbitrary shape using discrete segments on the body surface. One of the equations must be solved by time stepping, but the kernel matrix is identical at each step and need only be inverted once. The Fourier transform of the impulse-response function gives the more conventional added-mass and damping in the frequency domain. The results for arbitrary motions may be found as a convolution of the impulse response function and the time derivatives of the motion. Comparisons are shown between the time-domain computations and published results for a sphere in heave, a sphere in sway, and a right circular cylinder in heave. Theoretical predictions and experimental results for the heave motion of a sphere released from an initial displacement are also given. In all cases the comparisons are excellent.
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Zhang, Yuan, Yougang Sun, Zhouguo Hu, Baifu Fang, Ying Xie, Linkai Chen et Yuanyuan Teng. « Control Performance Analysis of Mining Ship Heave Compensation System Based on Fuzzy Logic Algorithm ». Journal Européen des Systèmes Automatisés 55, no 2 (30 avril 2022) : 213–20. http://dx.doi.org/10.18280/jesa.550208.
Texte intégralRésumé :
With the depletion of land resources, demands for marine resources mining is increasing, the mining vessels which is known as one of the most important offshore equipment are widely concerned. The motions of wave surges in the marine environment will affect the operation of mining vessels, especially for the heave motion which will cause serious disturbances to the mining vessels during operation, and even the damage of the hull structure and related mining facilities. Hence, it is very necessary to compensate for the heave motion of the mining vessel, and a hydraulic cylinder-based active-passive integrated composite heave compensation system is designed in this paper. Firstly, the structural composition and working principle of the heave compensation system are introduced, and its mathematical model is also established. Secondly, the frequency domain and time domain analysis are carried out using AQWA software to obtain the heave displacement response of the ship under regular and irregular waves of six sea states as the desired compensation displacement. Finally, the controller of the active-passive heave compensation system is designed, and a fuzzy logic control strategy based on Mamdani type is proposed, and the control performance is analyzed. The results show that the accuracy of the fuzzy logic control algorithm is better than the traditional PID control algorithm, and the laws and methods of PID adjustment are obtained, which proves that the fuzzy logic control algorithm has obvious advantages for engineering applications.
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Lian, Jijian, Junni Jiang, Xiaofeng Dong, Haijun Wang, Huan Zhou et Pengwen Wang. « Coupled Motion Characteristics of Offshore Wind Turbines during the Integrated Transportation Process ». Energies 12, no 10 (27 mai 2019) : 2023. http://dx.doi.org/10.3390/en12102023.
Texte intégralRésumé :
The offshore wind turbine (OWT) supported by bucket foundations can be installed in the integrated transportation process by a dedicated vessel. During the integrated transportation process, the wind turbine is considered as a coupling system with the transport ship, which is easily influenced by waves and storms. In view of the motion response and influential factors, the heave and rock stiffness of the entire floating system was proposed, and then the analytical dynamic motion model of the coupling system was established based on the movement mechanism of the traditional floating body in the wave in this paper. Subsequently, the rationality of the proposed motion model was verified based on the field observation data, with the maximum deviation of the motion responses less than 14%. Further, the influence on the heave and pitch motion of the coupling system considering different factors (vessel speed, wave height, wind speed and wave angle) and the factor sensitivity were discussed by the novel analytical model. It is explained that the heave and pitch motion responses rise with the increase of the wave height and wave angle. Simultaneously, the responses decrease as the vessel speed increases considering sailing along the waves. On the contrary, the responses show an obvious increasing trend with the increase of vessel speed in the case of the top wave sailing. In addition, it is also illustrated that the wave height has the greatest influence on the heave and pitch motion responses, followed by the vessel speed. The wave angle has the lowest sensitivity when the heave and pitch motion are far away from its harmonic resonance region.
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Nayfeh, All H. « On the Undesirable Roll Characteristics of Ships in Regular Seas ». Journal of Ship Research 32, no 02 (1 juin 1988) : 92–100. http://dx.doi.org/10.5957/jsr.1988.32.2.92.
Texte intégralRésumé :
In 1863 Froude observed that a ship whose frequency in pitch (heave) is twice its frequency in roll has undesirable roll characteristics. To explain this phenomenon, Paulling and Rosenberg as well as Kinney assumed the pitch (heave) motion to be a simple harmonic independent of the roll motion. Substituting the pitch (heave) expression into the roll equation, they obtained a Mathieu equation. They found that exponentially growing instabilities can occur for certain pitch amplitudes and frequency ratios. The exponential growth is unrealistic, the result of their neglecting the influence of the roll motion on the pitch (heave) motion. To improve their results, the present author offers an analysis for the nonlinear coupling of the pitch and roll modes of ship motions in regular seas. When the encounter frequency is near the pitch frequency, only the pitch mode is excited if the encountered wave amplitude (excitation amplitude) is small. As the excitation amplitude increases, the amplitude of the pitch mode increases in accordance with linear theory until it reaches a critical small value. As the excitation amplitude increases further, the pitch amplitude does not change from the critical value (that is, the pitch mode is saturated), and all the extra energy is transferred to the roll mode. Consequently, for large excitation amplitudes, the response is a combined roll and pitch motion, with the amplitude of the roll mode being very much larger than that of the pitch mode. More dangerously, the nonlinear theory predicts instabilities in regions where the linear theory predicts stability. Moreover, the nonlinear theory predicts conditions for the nonexistence of steady-state periodic responses. Instead, the responses can be amplitude- and phase-modulated roll and pitch motions or even chaotic. When the encounter frequency is near the roll frequency, there is no saturation phenomenon and, at close to perfect resonance, there are no steady-state periodic responses in some cases. The present results indicate that large roll amplitudes are likely in this case also. Further, the results predict the possibility of large amplitudes in the roll motion even when the ship is moving through a head or following sea.
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Zhai, Gang Jun, Xiao Jie Song, Wei Diao et Bin Bin Li. « Frequency Response Analysis of Truss Spar by Considering the Viscous Damping ». Applied Mechanics and Materials 105-107 (septembre 2011) : 208–15. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.208.
Texte intégralRésumé :
A calculation model for Truss Spars motion response is established under the wave action by combing the potential flow theory and the modified Morison equation. The high order boundary element method is used to acquire the wave exciting force and the relevant hydrodynamic information. By numerical simulation, the surge, heave and pitch s are obtained, and the parameter analysis for influence of Morison drag coefficient on responses are conducted. The calculated results indicate that the surge and pitch motions are only sensitivity to the drag coefficient in the low frequency range, and consequently the viscous damping would play an important role when the platform undergoes 2nd order wave slow drift force. For the heave response, the heave plates installed on the Truss Spar provide large vertical viscous damping which distinctly affects the heave .
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Hui, Li, Sun Zhiyong, Han Bingbing, Shao Yuhang et Deng Baoli. « RESEARCH ON THE MOTION RESPONSE OF AQUACULTURE SHIP AND TANK SLOSHING UNDER ROLLING RESONANCE ». Brodogradnja 73, no 2 (1 avril 2022) : 1–15. http://dx.doi.org/10.21278/brod73201.
Texte intégralRésumé :
The double-row and double-chamfered aquaculture tank is a special tank structure of the aquaculture ship. The tank sloshing of this structure is coupled with the hull motion, which has an important impact on the safety of the hull motion. In the present study, research on the tank sloshing and hull motion response of aquaculture ships was conducted based on the model seakeeping and tank sloshing tests in regular waves. The test results were compared with the numerical simulation results of solid loading without sloshing. The results showed that the numerical simulation of the pitch motion was consistent with the amplitude-frequency response curve of the experimental results. Under certain transverse wave conditions, a large discrepancy existed between the amplitude-frequency response curve of the heave motion by the numerical simulation and the test results, and the roll motion differed most from the experimental result. Severe roll resonance occurred when the wave length-ship length ratio was 0.6. The roll motion amplitude was increased by 183.2%. Therefore, compared with aquaculture ships without sloshing, the sloshing of the tank has little effect on the pitch but has a great impact on the roll and heave motions, with the most significant effect on the roll motion.
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Zeng, Zhi Gang, et Guo Hua Chen. « Adaptive Predictive Based on Equal-Dimension and New Information for the Hydraulic Mechanism of Wave Motion Compensating Platform ». Applied Mechanics and Materials 20-23 (janvier 2010) : 236–42. http://dx.doi.org/10.4028/www.scientific.net/amm.20-23.236.
Texte intégralRésumé :
A wave motion compensating platform has the function of compensating the ship’s generalized heave motion (a coupling result of roll, pitch and heave). It can decrease the impact of ship motion on some sea works and equipments. The hydraulic mechanism of platform system has the characteristics of nonlinear and big inertia. In order to compensate generalized heave motion effectively, an adaptive predictive control policy is used for controlling the hydraulic mechanism. Based on equal-dimension and new information, an automation regressive model can get adaptive multi-step prediction. The model parameter estimation based on the least square algorithm is easy to blow up and be unstable when the system has random noise. To improve the problem solution, a damped recursive least square algorithm is proposed to estimate the parameters on line. For the short regulation time, strong anti-disturbance ability and great robustness, a nonlinear PID controller whose gain parameters vary with errors is suitable for controlling the hydraulic mechanism. Using the collected experimental data, the simulations suggest that adopting the above adaptive predictive control policy to control hydraulic mechanism is able to decrease the generalized heave amplitude of wave motion compensating platform.
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Mahfouz, Ayman B., Mahmoud R. Haddara et Christopher D. Williams. « Prediction of the Hydrodynamic Parameters in the Coupled Heave and Pitch Motion Equations for Underwater Robotic Vehicles Using Measured Responses at Sea ». Journal of Offshore Mechanics and Arctic Engineering 123, no 3 (20 avril 2001) : 93–102. http://dx.doi.org/10.1115/1.1382593.
Texte intégralRésumé :
A method for the identification of the damping, restoring, and coupling parameters in the equations describing the coupled heave and pitch motions for an underwater robotic vehicle (URV) sailing near sea surface in random waves using only its measured responses at sea is presented. The random decrement equations are derived for the URV performing coupled heave and pitch motions in random waves. The hydrodynamic parameters in these equations are identified using a new identification technique called RDLRNNT, which uses a combination of a multiple linear regression algorithm and a neural networks technique. The combination of the classical parametric identification techniques and the neural networks technique provides robust results and does not require a large amount of computer time. The developed identification technique would be particularly useful in identifying the parameters for both moderately and lightly damped motions under the action of unknown excitations effected by a realistic sea. Numerically generated data for the coupled heave and pitch motion of a URV are used initially to test the accuracy of the technique. Experimental data are also used to validate the identification technique. It is shown that the developed technique is reliable in the identification of the parameters in the equations describing the coupled heave and pitch motions for an URV.
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Zhu, Qidan, et Yu Ma. « H2/H∞ Antivertical Controller Based on Particle Swarm Optimization (PSO) Using Active T-Foils and Trim Tabs for a Fast Catamaran ». Mathematical Problems in Engineering 2019 (13 octobre 2019) : 1–17. http://dx.doi.org/10.1155/2019/4868473.
Texte intégralRésumé :
A wave-piercing catamaran (WPC) is a high-performance ship that has been developed in recent years. Compared to other common ships, the WPC has higher lateral stability, larger deck area, lower oil consumption, and higher speed. However, under rough seas and at high speeds, the coupled heave/pitch motions of the WPC can easily produce coupled oscillations that seriously affect its seaworthiness. To solve these problems, a ride control system was designed for the WPC in this study. This system comprises two T-foils, two trim tabs, and a catamaran motion controller. The H2/H∞ controller was designed based on memory-based particle swarm optimization to alleviate the coupled oscillation resulting from heave/pitch motions. Numerical simulations were conducted to validate the proposed method, and the results showed that the proposed motion controller could obviously improve the sea-keeping performance of a WPC.
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AlaviMerh, Javad, Jason Lavroff, Michael R. Davis, Damien S. Holloway et Giles A. Thomas. « An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 1 : Reduction of Ship Motions ». Journal of Ship Research 61, no 01 (1 mars 2017) : 35–49. http://dx.doi.org/10.5957/jsr.2017.61.1.35.
Texte intégralRésumé :
Ride control systems are essential for comfort and operability of high-speed ships, but it remains an open question what is the optimum ride control method. To investigate the motions of a 112-m high-speed catamaran fitted with a ride control system, a 2.5-m model was tested in a towing tank. The model active control system comprised two transom stern tabs and a central T-Foil beneath the bow. Six ideal motion control feedback algorithms were used to activate the model scale ride control system and surfaces in a closed-loop control system: heave control, local motion control, and pitch control, each in a linear and nonlinear version. The responses were compared with the responses with inactive control surfaces and with no control surfaces fitted. The model was tested in head seas at different wave heights and frequencies and the heave and pitch response amplitude operators (RAOs), response phase operators, and acceleration response were measured. It was found that the passive ride control system reduced the peak heave and pitch motions only slightly. The heave and pitch motions were more strongly reduced by their respective control feedback. This was most evident with nonlinear pitch control, which reduced the maximum pitch RAO by around 50% and the vertical acceleration near the bow by about 40% in 60-mm waves (2.69 m at full scale). These reductions were influenced favorably by phase shifts in the model scale system, which effectively contributed both stiffness and damping in the control action.
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Fitriadhy, Ahmad, Nurul Aqilah Mansor et Nur Adlina Aldin. « Heave and Pitch Motions of a Towed Ship in Waves Incorporated with an Asymmetrical Bridle Towline Model ». EPI International Journal of Engineering 2, no 1 (27 juin 2019) : 34–40. http://dx.doi.org/10.25042/epi-ije.022019.07.
Texte intégralRésumé :
Investigation of a ship towing system performance in waves incorporated with an asymmetrical towline configuration is necessarily to be studied to ensure a towing safety of navigation. To achieve the objective, this paper presents the ship towing motion performance in waves using Computational Fluid Dynamic (CFD) approach. Here, the heave and pitch motions of the towed ship so-called barge has been analysed, where several effects of the towing angle and towing speeds have been taken into account. In the calm water condition, the results revealed that the increase of tow angle was proportional with the sufficient reduction of the sway amplitude motion and inversely proportional to her yaw motion. The increase of the asymmetrical tow angle, however, has led to increase her sway motion amplitude in wave condition and conversely reduced the tow speed increased. In addition to the pitch motion characteristic, it subsequently increased by 12.1% as the tow angle raised from 25° to 35°; meanwhile the pitch motion of barge has by 10.2% as the tow speed increased from 0.655 m/s to 0.728 m/s. This CFD simulation is very useful as the preliminary prediction on the heave and pitch motion characteristics ensure a safety navigation of a towed ship in waves.
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Sang, Song, Yuan Zhou et Xue Liang Jiang. « Study on Nonlinear Motion Behavior of Coupled Heave-Pitch for the Classic Spar Platform Based on AQWA ». Applied Mechanics and Materials 170-173 (mai 2012) : 2170–74. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.2170.
Texte intégralRésumé :
This paper used AQWA software to research the nonlinear motion characteristic of heave-pitch coupling of classical Spar platform in regular waves. With classic Spar platform as an example, the wave amplitude and periodic changes’ effect to the nonlinear motion behavior of coupled heave-pitch is researched. After calculation, the critical periods corresponding to the different incident wave amplitude are obtained, based which, gets the instability parameter domain of coupling resonance of platform in the wave period-amplitude plane. The results in this paper show that the heave-pitch coupled resonance of platform depends on the wave amplitude and the ratio of the natural period of heave and pitch, and the incident wave period.
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Im, Namkyun, et Sangmin Lee. « Effects of Forward Speed and Wave Height on the Seakeeping Performance of a Small Fishing Vessel ». Journal of Marine Science and Engineering 10, no 12 (7 décembre 2022) : 1936. http://dx.doi.org/10.3390/jmse10121936.
Texte intégralRésumé :
The effects of wave height and forward speed on the seakeeping performance of a small fishing vessel in irregular waves are evaluated using computational fluid dynamics (CFD). The wave height effect changed linearly for a forward speed in the head sea and beam sea. In the stationary state, the heave and roll motions attributed to the wave height appear nonlinearly. The effect of the speed showed a non-linear shape wherein the heave motion became larger with an increase in the forward speed in beam sea. The seakeeping performance of pitch motion is greatly improved at forward speed rather than in a stationary state. The seakeeping performance of the roll motion is more dangerous than the pitch motion, regardless of wave height and vessel speed. The mean roll period in irregular waves is obtained through this study, and it is longer than the natural roll period in still water. It is necessary to be careful as the probability of exceeding the limit is high and GM is decreased in transverse waves.
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Ibrahim, R. A., et I. M. Grace. « Modeling of Ship Roll Dynamics and Its Coupling with Heave and Pitch ». Mathematical Problems in Engineering 2010 (2010) : 1–32. http://dx.doi.org/10.1155/2010/934714.
Texte intégralRésumé :
In order to study the dynamic behavior of ships navigating in severe environmental conditions it is imperative to develop their governing equations of motion taking into account the inherent nonlinearity of large-amplitude ship motion. The purpose of this paper is to present the coupled nonlinear equations of motion in heave, roll, and pitch based on physical grounds. The ingredients of the formulation are comprised of three main components. These are the inertia forces and moments, restoring forces and moments, and damping forces and moments with an emphasis to the roll damping moment. In the formulation of the restoring forces and moments, the influence of large-amplitude ship motions will be considered together with ocean wave loads. The special cases of coupled roll-pitch and purely roll equations of motion are obtained from the general formulation. The paper includes an assessment of roll stochastic stability and probabilistic approaches used to estimate the probability of capsizing and parameter identification.
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Thiagarajan, Krish, et Javier Moreno. « Wave Induced Effects on the Hydrodynamic Coefficients of an Oscillating Heave Plate in Offshore Wind Turbines ». Journal of Marine Science and Engineering 8, no 8 (18 août 2020) : 622. http://dx.doi.org/10.3390/jmse8080622.
Texte intégralRésumé :
The research problem discussed in this paper is of relevance to floating offshore wind turbine design, where heave plates are attached to the columns of a semi-submersible in order to improve vertical plane stability and the power output. Because of the shallow draft of these structures, the heave plates are proximal to the water surface. When subject to vertical plane motions the flow around a plate is altered by the presence of the free surface, resulting in changes in added mass and damping forces. In this paper, we present the experimental results for the added mass and damping coefficients for circular heave plates attached to a column, when oscillating in heave in the presence of oncoming waves. The results tend to indicate that applying the hydrodynamic coefficients obtained from still water experiments for a structure moving in waves may only be an approximation. For different relative phases of the wave and the motion, large variations could occur. We define a modified Keulegan—Carpenter (KC) number that depends on the relative amplitude of motion with respect to the wave. With this definition, the added mass and damping values are seen to be closer to the still water trends. However, at lower KC values, the added mass coefficients could differ by 30%, which can affect natural frequency estimates. Thus, caution needs to be exerted in the selection of hydrodynamic coefficients for heave plates oscillating in proximity to the free surface.
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Ghadimi, Parviz, Sasan Tavakoli, Abbas Dashtimanesh et Pouria Taghikhani. « Dynamic response of a wedge through asymmetric free fall in 2 degrees of freedom ». Proceedings of the Institution of Mechanical Engineers, Part M : Journal of Engineering for the Maritime Environment 233, no 1 (14 novembre 2017) : 229–50. http://dx.doi.org/10.1177/1475090217733150.
Texte intégralRésumé :
In this article, a mathematical model is presented for simulation of the coupled roll and heave motions of the asymmetric impact of a two-dimensional wedge body. This model is developed based on the added mass theory and momentum variation. To this end, new formulations are introduced which are related to the added mass caused by heave and roll motions of the wedge. These relations are developed by including the asymmetrical effects and roll speed. In addition, by considering the roll speed, a particular method is presented for the time derivative of half-wetted beam of an asymmetric wedge. Furthermore, two equations are derived for the roll and heave motions in which damping terms appear. Validity of the proposed method is verified by comparing the predicted results against available experimental data in two conditions of roll motion and no roll motion. Favorable agreement is observed between the predicted results and experimental data. The pressure and hydrodynamic load are computed, and the differences between the results associated with the considered conditions are explored. Subsequently, the effects of different physical parameters including deadrise angle, initial roll angle, and initial velocity on the dynamic response of a two-dimensional wedge section are investigated. Ultimately, time histories of hydrodynamic coefficients are determined in order to provide a better understanding of the derived equations.
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Takata, Taisuke, Mayuko Takaoka, Hidetaka Houtani, Kentaro Hara, Sho Oh, Edgard B. Malta, Kazuhiro Iijima, Hideyuki Suzuki et Rodolfo T. Gonçalves. « Effect of Heave Plates on the Wave Motion of a Flexible Multicolumn FOWT ». Energies 15, no 20 (14 octobre 2022) : 7605. http://dx.doi.org/10.3390/en15207605.
Texte intégralRésumé :
Three models with different footing types were used to clarify the effect of heave plates on the hydrodynamic behavior of the elastic response of a flexible multicolumn floating offshore wind turbine (FOWT). The models were tested under regular waves, whose added mass, damping, and motion response results were compared with numerical simulations by NK-UTWind and WAMIT codes. As a whole, the attachment of heave plates was responsible for increasing the added mass and damping levels, consequently modifying the RAO of the models. Regarding the response in a sea condition, a decrease of 33% and 66% of the significant motion height (heave and pitch) was observed. Thus, the heave plate can be a good feature for the future design of FOWT.
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Huang, Ya Xin, Bing Wang et Jun Yi Liu. « Force Analysis of the Anchor Chains and the Cable in the Crane-System with a Floating Base in Regular Waves ». Applied Mechanics and Materials 494-495 (février 2014) : 321–27. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.321.
Texte intégralRésumé :
In order to analyze the force of the anchor chains and the cable in the crane-system with a floating base, firstly the system is simplified to two-rigid-body model and the anchor chains in the system are in symmetric layout; then the motion response of the system as well as the force of the anchor chains and the cable are solved by use of discrete time transfer matrix method, lastly the time history curves of motion of the system and the force of the anchor chains and the cable are obtained. The results of numerical simulation show that the roll motion has greater influences on the system comparing with sway and heave, the amplitudes of sway and heave are small. Furthermore, the force of the anchor chains are mainly caused by the roll motion while the force caused by sway and heave are relatively small.
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Yuan, Zhi Jiang, Lian Gan Jin, Wei Chi et Heng Dou Tian. « Couple Model for Predicting Behaviors of Underwater Towed Systems under Effect of Heave and Pitch Motion of Ship ». Advanced Materials Research 629 (décembre 2012) : 581–86. http://dx.doi.org/10.4028/www.scientific.net/amr.629.581.
Texte intégralRésumé :
Underwater towed systems have the many applications in exploitation of underwater environments. While in the research exists which is about the numerical models of towed system, the relatively simple model of the towed body is used and the dynamic of the towing ship is neglected. The towing ship as part of towed system, its heave and pitch motion are coupled and highly non-linear. Considering the dynamic of three parts of towed system is important. In the paper, a newly couple model is developed to predict the behaviors of underwater towed systems under effect of the heave and pitch motion of towing ship. We use a finite difference method as the towed cable and is coupled with the non-linear numerical models of a towing ship and a towed body. Illustrative application of the coupling model is presented. The numerical results show the heave and pitch motion of towing ship affect the motion of towed body.
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Le, Cong Huan, Hong Yan Ding, Guo Hai Dong et Pu Yang Zhang. « Experimental Research on the Influences of Wave Height on Towing of 4-Bucket Foundation Platform ». Advanced Materials Research 243-249 (mai 2011) : 4723–27. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4723.
Texte intégralRésumé :
Internal air pressure and water pressure of the buckets foundation, acceleration and dragging force of the 4-bucket foundation platform were determined to analyze the influences of wave height on towing when 4-Bucket foundation platform is towing in conditions of a certain towing velocity, mooring point position and draught in different regular waves based on the model test. Comparing platform towing in following and head waves, the heave motion of the latter is more strenuous than that of the former; the stability and seakeeping of the former is better than those of the latter. Roll motion, pitch motion and heave motion appear aggravate phenomenon with the increase of wave height.
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Colling, Jacob K., Saeed Jafari Kang, Esmaeil Dehdashti, Salman Husain, Hassan Masoud et Gordon G. Parker. « Free-Decay Heave Motion of a Spherical Buoy ». Fluids 7, no 6 (27 mai 2022) : 188. http://dx.doi.org/10.3390/fluids7060188.
Texte intégralRésumé :
We examined the heave motion of a spherical buoy during a free-decay drop test. A comprehensive approach was adopted to study the oscillations of the buoy involving experimental measurements and complementary numerical simulations. The experiments were performed in a wave tank equipped with an array of high-speed motion-capture cameras and a set of high-precision wave gauges. The simulations included three sets of calculations with varying levels of sophistication. Specifically, in one set, the volume-of-fluid (VOF) method was used to solve the incompressible, two-phase, Navier–Stokes equations on an overset grid, whereas the calculations in other sets were based on Cummins and mass-spring-damper models that are both rooted in the linear potential flow theory. Excellent agreements were observed between the experimental data and the results of VOF simulations. Although less accurate, the predictions of the two reduced-order models were found to be quite credible, too. Regarding the motion of the buoy, the obtained results indicate that, after being released from a height approximately equal to its draft at static equilibrium (which is about 60% of its radius), the buoy underwent nearly harmonic damped oscillations. The conducted analysis reveals that the draft length of the buoy has a profound effect on the frequency and attenuation rate of the oscillations. For example, compared to a spherical buoy of the same size that is half submerged at equilibrium (i.e., the draft is equal to the radius), the tested buoy oscillated with a period that was roughly 20% shorter, and its amplitude of oscillations decayed almost twice faster per period. Overall, the presented study provides additional insights into the motion response of a floating sphere that can be used for optimal buoy design for energy extraction.
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Woodacre, J. K., R. J. Bauer et R. A. Irani. « A review of vertical motion heave compensation systems ». Ocean Engineering 104 (août 2015) : 140–54. http://dx.doi.org/10.1016/j.oceaneng.2015.05.004.
Texte intégral
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Li, Zhen Lin, Hong Feng Sun et Meng Lan Duan. « Application of a New Heave Compensation System for Deepwater Hardware Installation ». Advanced Materials Research 468-471 (février 2012) : 97–102. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.97.
Texte intégralRésumé :
In order to minimize the adverse effects of the vessel’s heaving motion on offshore operations, this paper presents a Composite Heave Compensation System for deepwater hardware installation, which overcomes the shortcomings of conventional Heave Compensation System.
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Holmes, Samuel, Shankar Bhat, Pierre Beynet, Anil Sablok et Igor Prislin. « Heave Plate Design With Computational Fluid Dynamics ». Journal of Offshore Mechanics and Arctic Engineering 123, no 1 (18 septembre 2000) : 22–28. http://dx.doi.org/10.1115/1.1337096.
Texte intégralRésumé :
Computational fluid dynamics (CFD) methods are used to predict the hydrodynamic loads on heave plates. A series of numerical simulations for plates undergoing simple harmonic motion is used to determine the force and moment resultant histories. Then a least mean squares method is used to obtain the appropriate Morison coefficients for the plates under a variety of sea conditions. Finally, force and moment histories are predicted for a plate on a floating platform excited by a random sea motion.