CALCULATION OF THE HYDRODYNAMIC INTERACTION BETWEEN TWO ENCOUNTERING BODIES IN COUPLING MULTI-FREEDOM MOTIONS

2021 ◽  
Vol 157 (A4) ◽  
Author(s):  
H M WANG ◽  
L WANG ◽  
L Q TU ◽  
C H ZHAO

ellipsoids are taken as an example. By coupling the motion equations of the two bodies and the fluid flow equations, the interaction forces and moments are calculated, and the tracks are predicted. The numerical results for the model fixed motion (only free to surge) at constant speed are compared with those published in literature for the validation of the method proposed in this paper, and good agreement is found. On this basis, more complicated multi-degree of freedom motions in surge, sway and yaw directions induced by the interaction effects are simulated. By systematically comparing and analyzing the numerical results obtained at different speeds, lateral distances and body sizes, the influences of speed and lateral distance and body size The sway and yaw motion will be induced additionally due to the interaction effects when two encountering bodies sail in close proximity, which may lead to the collision accident. In the present study, two on the hydrodynamic forces are elucidated. 

2015 ◽  
Vol 157 (A4) ◽  
pp. 219-226

"The sway and yaw motion will be induced additionally due to the interaction effects when two encountering bodies sail in close proximity, which may lead to the collision accident. In the present study, two ellipsoids are taken as an example. By coupling the motion equations of the two bodies and the fluid flow equations, the interaction forces and moments are calculated, and the tracks are predicted. The numerical results for the model fixed motion (only free to surge) at constant speed are compared with those published in literature for the validation of the method proposed in this paper, and good agreement is found. On this basis, more complicated multi-degree of freedom motions in surge, sway and yaw directions induced by the interaction effects are simulated. By systematically comparing and analyzing the numerical results obtained at different speeds, lateral distances and body sizes, the influences of speed and lateral distance and body size on the hydrodynamic forces are elucidated."


2017 ◽  
Vol 159 (A4) ◽  
Author(s):  
N Jayarathne ◽  
D Ranmuthugala ◽  
Z Leong ◽  
J Fei

To date, most of the hydrodynamic interaction studies between a tug and a ship during ship assist manoeuvers have been carried out using model scale investigations. It is however difficult to establish how well results from these studies represent full scale interaction behaviour. This is further exacerbated by the lack of proven methodologies to non-dimensionalise the relative distances between the two vessels, enabling the comparison of model and full scale interaction effect data, as well as between vessels of dissimilar size ratios. This study investigates a suitable correlation technique to non-dimensionalise the lateral distance between vessels of dissimilar sizes, and a scaling option for interaction effect studies. It focuses on the interaction effects on a tug operating around the forward shoulder of a tanker at different lateral distances during ship assist operations. The findings and the non-dimensioning method presented in this paper enable the interaction effects determined for a given ship-to-tug ratio to be used to predict the safe operational distances for other ship-to-tug ratios.


Author(s):  
N Jayarathne ◽  
D Ranmuthugala ◽  
Z Leong ◽  
J Fei

To date, most of the hydrodynamic interaction studies between a tug and a ship during ship assist manoeuvers have been carried out using model scale investigations. It is however difficult to establish how well results from these studies represent full scale interaction behaviour. This is further exacerbated by the lack of proven methodologies to non- dimensionalise the relative distances between the two vessels, enabling the comparison of model and full scale interaction effect data, as well as between vessels of dissimilar size ratios. This study investigates a suitable correlation technique to non-dimensionalise the lateral distance between vessels of dissimilar sizes, and a scaling option for interaction effect studies. It focuses on the interaction effects on a tug operating around the forward shoulder of a tanker at different lateral distances during ship assist operations. The findings and the non-dimensioning method presented in this paper enable the interaction effects determined for a given ship-to-tug ratio to be used to predict the safe operational distances for other ship-to-tug ratios.


2019 ◽  
Vol 72 (3) ◽  
pp. 813-831
Author(s):  
Nirman Jayarathne ◽  
Dev Ranmuthugala ◽  
Zhi Leong

The hydrodynamic interaction effects on a tug operating in close proximity to a larger vessel can result in dangerous situations for the tug. To date most studies have focussed on the interaction effects between the vessels when they are operating in parallel, which represent only one of many practical ship-assist manoeuvres. It is therefore necessary to investigate a wide range of tug-ship combinations to obtain a detailed understanding of these effects. This paper discusses the hydrodynamic interaction effects on a tug operating at various relative positions and drift angles to a larger ship, both moving together at the same forward speed. The hydrodynamic effects were determined using Computational Fluid Dynamics (CFD) simulations that were validated using captive model test data. The range of manoeuvres discussed in this paper provides a comprehensive overview of the hydrodynamic interaction effects on a tug enabling tug operators to identify safe operating envelopes for their vessels.


Author(s):  
Joa˜o Pessoa ◽  
Nuno Fonseca ◽  
C. Guedes Soares

The paper studies the hydrodynamic interactions between two bodies in close proximity oscillating on the free surface due to incident harmonic waves, inspired in the problem of offloading from a LNG floating platform to a tanker. It deals with a modified Wigley hull and a rectangular barge arranged side by side. The numerical results include hydrodynamic coefficients, exciting forces, absolute motions, and drift forces, and they are compared with published experimental data followed by further analysis of the effects of free surface elevation between the two bodies. The calculations are carried out with the WAMIT® code, which is based on a panel method, or boundary integral method.


Author(s):  
Kjell Herfjord ◽  
Tore Holma˚s

A method for predicting interaction between risers is presented. The method is efficient and handles different riser systems exposed to complex environmental data. To achieve this, the method utilizes pre-established data for forces on risers in close proximity. Interaction effects concerning mean values as well as the dynamic forces at vortex shedding frequencies are stored. The interaction effects cause large wake induced oscillations (WIO), and the vortex induced vibrations (VIV) are influenced as well. The method uses the database of forces in a strip theory manner to obtain excitation forces on risers and other slender bodies exposed to current. The method is implemented in a non-linear dynamic finite element tool, HYBER. During the simulation, the clearance between the risers is followed up. If collisions occur, relevant data are recorded, and the simulation continues. Fatigue and possible single event damage are assessed. In the present paper, results from the method are compared with comprehensive measurements in model scale, and the computed results show good agreement with the measurements. Databases exist for bare cylinders with equal and unequal diameters as well as for two geometries of strakes.


Author(s):  
Renato Skejic ◽  
Kensuke Kirimoto ◽  
Tor E. Berg ◽  
Egil Pedersen

The development of a generalized navigation safety standard for ships performing underway lightering maneuvers in close proximity has been considered from an operational viewpoint. In general, it is well known that the safety and efficiency of a maritime operation between two ships at close range represents a challenging and demanding task to mariners. The main reason is related to unfamiliar maneuvering behavior of the involved ships and consequently a poor decision-making process due to lack of knowledge and understanding of ship-to-ship interaction effects. Operational challenges in ship-to-ship lightering can be reduced through an increased knowledge and understanding of the hydrodynamic interaction effects. This paper discusses how to perform the lightering maneuver in the final approach phase until the lateral distances are reduced to the fender diameter. Visualization of ‘Collision Danger Zones’ due to hydrodynamic interaction is proposed to be introduced in a decision-support tool to assist the pilot/master to control the approach phase of the ship-to-ship operation and thus improve the overall operational safety.


Author(s):  
Р. Али ◽  
Н.В. Тряскин

Эксплуатация судна сопровождается ситуациями, в которых оно испытывает дополнительные нагрузки от близости твёрдых границ, таких как плавание в ограниченном фарватере, расхождение судов на малых расстояниях, погрузочные операции. Для грамотного осуществления подобных операций необходима заблаговременная оценка возможные нагрузок и учёт гидродинамического влияния между судами или судном и твёрдой поверхностью. Целью данной работы является изучение влияния взаимного положения двух судов на гидродинамическое взаимодействие между ними, а также оценка возможного взаимодействия между судами при операциях погрузки/разгрузки на глубокой воде. Гидродинамическое взаимодействие выражается в изменении полей давления и скорости при непосредственной близости нескольких судов, изменении поперечной и продольной гидродинамических сил и моментов рыскания, действующих на оба объекта. Для определения влияния относительных расстояний между судами на их гидродинамическое взаимодействие во время разгрузочных операций проведён ряд численных экспериментов. Смоделировано обтекание потоком вязкой несжимаемой жидкости двух судов типа KVLCС2, находящихся на различных относительных расстояниях друг от друга. Математическое моделирование турбулентного потока основано на решении уравнений Рейнольдса и проведено с помощью открытого программного пакета OpenFOAM. Для моделирования турбулентности использована модель турбулентности. Результаты численного моделирования обработаны и проанализированы, они находятся в хорошем соответствии с экспериментальными данными. Вычислены максимальные силы и моменты, возникающие при взаимодействии судов при их различном взаимном положении. Hydrodynamic interaction between ships continues to be a major field of research, considering that during different stages of the investment ship’s life, ship is exposed to the presence of a close rigid boundary such as sailing in restricted areas, overtaking and encountering at small distances with other ship or during investment operation such as lightering operations. In order to perform lightering operations safely, the knowledge of the interaction effects between both ships is very important. The aim of this article is to study the changes in velocity and pressure fields resulting from the presence of the two ships in close proximity, evaluating the longitudinal and transverse forces as well as yaw momentum affecting both ships, determining their relationship to the relative longitudinal position of the two ships as well as to predict the ship-to-ship interaction during lightering operations in deep water. A series of systematic computations were performed on two KVLCC2 hulls advancing in deep water and calm weather with the same constant low speed (full scale speed 4kt) in order to investigate the influence of the relative longitudinal separations on the hydrodynamic interaction forces and moments during the lightering operation. OpenFOAM, an open-source CFD packet was used for carrying out the simulations, RANS method was used for turbulence modeling and the well-known turbulent model was used to close RANS equations. Numerical results have been post-processed, analyzed, compared and found to be of a good agreement with the experimental results. Maximum forces and moments and their relation with longitudinal position were computed.


1984 ◽  
Vol 28 (01) ◽  
pp. 70-75
Author(s):  
C. C. Hsu

Simple wall correction rules for two-dimensional and nearly two-dimensional cavity flows in closed or free jet water tunnels, based on existing linearized analyses, are made. Numerical results calculated from these expressions are compared with existing experimental findings. The present theoretical predictions are, in general, in good agreement with data.


Author(s):  
Kang-Jia Wang ◽  
Hong-Wei Zhu

Abstract The Kundu-Mukherjee-Naskar equation can be used to address certain optical soliton dynamics in the (2+1) dimensions. In this paper, we aim to find its periodic wave solution by the Hamiltonian-based algorithm. Compared with the existing results, they have a good agreement, which strongly proves the correctness of the proposed method. Finally, the numerical results are presented in the form of 3-D and 2-D plots. The results in this work are expected to shed a bright light on the study of the periodic wave solution in physics.


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