A Numerical Study on Hydrodynamic Interactions Between Large Numbers of Multiple Floating Bodies

2003 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Mir Tareque Ali
Keyword(s):  
Numerical Study ◽  
Computer Code ◽  
Hydrodynamic Forces ◽  
Hydrodynamic Interactions ◽  
Physical Aspect ◽  
Floating Bodies ◽  
Coupled Equations ◽  
Large Numbers ◽  
Exciting Forces ◽  
Multi Body

This paper investigates the hydrodynamic interactions between large numbers of multiple bodies floating in each other’s close vicinity. The physical aspect of hydrodynamic interaction is rather complicated and numerically sound scheme is highly recommended to study this complex phenomenon. In the present study, the 3D sink-source method has been adopted to determine the hydrodynamic forces by taking into account the effect of hydrodynamic interactions among the different floating bodies, and the coupled equations of motions are solved directly. The validation of the computer code developed for this purpose has been justified by comparing the present results with that of the published ones for simple geometrical shaped floating bodies. The numerical computations have been carried out for different numbers of various freely floating multi-body systems and the hydrodynamic interactions between the floating bodies have been studied by calculating the hydrodynamic forces, first order wave exciting forces and motion responses. Finally some conclusions have been drawn on the basis of the present analysis.

On Hydrodynamic Interaction Between Several Freely Floating Vertical Cylinders in Waves

2005 ◽  
Author(s):  
Mir Tareque Ali ◽  
Gazi Md. Khalil
Keyword(s):  
Interaction Effect ◽  
Hydrodynamic Interaction ◽  
Computer Code ◽  
Separation Distance ◽  
Numerical Results ◽  
Physical Aspect ◽  
Floating Bodies ◽  
Exciting Forces ◽  
Source Sink ◽  
Vertical Cylinders

This paper investigates the hydrodynamic interaction between several vertical cylinders freely floating in each other’s close vicinity. The physical aspect of hydrodynamic interaction is rather complicated and numerically accurate scheme is highly recommended to study this complex phenomenon. In the present study, 3D source-sink method has been adopted to determine the hydrodynamic coefficients and wave exciting forces by taking into account accurately the effect of hydrodynamic interaction among the different floating bodies. In order to check the convergence of numerical results, mean wetted surface of the floating cylinders are divided into different numbers of rectangular panels. A computer code is developed using 3D source-sink formulations and the validation of the computer code has been justified by comparing the present results with that of the published ones. In order to study the interaction effect, numerical results for a single cylinder have been compared with those of the multi-cylinder ones. The separation distance between the cylinders has been varied to examine the interaction effect for head sea condition. Finally some conclusions have been drawn on the basis of the present analysis.

A Numerical Investigation Into Hydrodynamic Interaction Coefficients for Multiple Freely Floating Bodies in Waves

2020 ◽  
Author(s):  
Mir Tareque Ali
Keyword(s):  
Hydrodynamic Interaction ◽  
Three Dimensional ◽  
Computer Code ◽  
Source Distribution ◽  
Hydrodynamic Coefficients ◽  
Body System ◽  
Regular Waves ◽  
Floating Bodies ◽  
Interaction Coefficients ◽  
Multi Body

Abstract When two or more bodies are floating in waves in each other’s vicinity, the fluid loading on the separate bodies will be influenced by the presence of the neighboring bodies. The wave loads on each body are affected, because of sheltering or wave-reflection effects due to the presence of surrounding floating body, while additional loads are exerted by the radiated waves, which are produced by the motions of the neighboring bodies. For a multi-body system, it is important to accurately compute the hydrodynamic coefficients and interaction coefficients, since these parameters will be used later to solve the 6xN simultaneous equations to predict the motion responses (where N is the number of freely floating bodies in the multi-body system). This paper aims to investigate the hydrodynamic interaction coefficients for two three dimensional (3-D) bodies floating freely in each other’s vicinity. Since the nature of hydrodynamic interaction is rather complex, it is usually recommended to study this complicated phenomenon using numerically accurate scheme. A computer code developed using 3-D source distribution method which is based on linear three-dimensional potential theory is used and the validation of the computer code has been justified by comparing the present results with that of the published ones for hydrodynamic coefficients and interaction coefficients of two bodies closely floating in regular waves. The calculated results for box-cylinder model are compared with the published results and the agreement is quite satisfactory. Numerical simulations are further conducted for two closely floating rectangular barges of side-by-side position in regular waves. During the computations of hydrodynamic coefficients and interaction coefficients for multi-body model, the separation distance between the floating bodies have been varied. Finally, some conclusions are drawn on the basis of the present analysis.

A Study of Slowly Varying Drift Forces on Multi-Body Floating System

2002 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Mir Tareque Ali
Keyword(s):  
Computer Code ◽  
Offshore Structures ◽  
Field Method ◽  
Vital Role ◽  
Numerical Accuracy ◽  
Natural Period ◽  
Floating System ◽  
Exciting Forces ◽  
Multi Body ◽  
Drift Forces

The mean and slowly varying drift forces play a vital role in the study of the behavior of moored offshore structures, because their mean periods are close to the natural period of oscillation of the system that causes large motion amplification. The present study is based on far-field method where the velocity potential is calculated by 3D sink-source technique. The numerical calculations have been carried out for a parallel arrangement of FPSO and an LNG carrier. The numerical accuracy in the determination of the wave exciting forces and the hydrodynamic reacting forces influences the motion response that eventually affects the drift forces and moments of each body. The computations of motion responses and drift forces are carried out for a number of different wave heading angles and for different separation distances between the FPSO and LNG carrier. The numerical results are compared with the experimental ones to justify the validity of the improved numerical accuracy of the present computations. It has been observed that due to the lack of accuracy in the numerical scheme adopted for the computer code, the computed results of drift forces and moments sometimes shows completely opposite trend than that of the experimental ones.

A Numerical Investigation on Hydrodynamic Interaction Coefficients for a Group of Truncated Composite Cylinders Floating in Waves

2021 ◽  
Author(s):  
Mir Tareque Ali
Keyword(s):  
Hydrodynamic Interaction ◽  
Three Dimensional ◽  
Computer Code ◽  
Source Distribution ◽  
Floating Body ◽  
Body System ◽  
Floating Bodies ◽  
Interaction Coefficients ◽  
Distribution Method ◽  
Multi Body

Abstract When a group of bodies are floating closely in waves, the fluid loading on these bodies will be influenced due to the presence of the neighboring bodies. The wave loading on each of these bodies are affected, because of the sheltering or wave-reflection effects due to the presence of surrounding floating bodies, while additional loads are exerted by the radiated waves produced by the motions of the nearby floating bodies. For a multiple floating body system, it is important to precisely compute the hydrodynamic interaction coefficients, since these parameters will be used later to solve the 6xN simultaneous equations to predict the motion responses (where N is the number of freely floating bodies in the multi-body system). On the other hand, the hydrodynamic interaction coefficients are absent for an isolated floating body case. This paper investigates the hydrodynamic interaction coefficients for a group of three dimensional (3-D) bodies floating freely in each other’s vicinity. Since the nature of hydrodynamic interaction is rather complex, it is usually recommended to study this complicated phenomenon using numerically accurate scheme. A computer code developed using 3-D source distribution method which is based on linear three-dimensional potential theory is used and the validation of the computer code has been justified by comparing the present results with that of the published ones for the hydrodynamic interaction coefficients of multiple bodies. The agreement between the calculated results with those of the published ones is quite satisfactory. Numerical simulations are further conducted for a group of identical truncated composite circular cylinders floating vertically at close proximity in regular waves. During the computations of hydrodynamic interaction coefficients of this multi-body model for different groups, the number of members in the group as well as the gap width among them has been varied. The paper also examines the occurrence of hydrodynamic resonances in the gap among the floating bodies and the presence of spikes with rapid fluctuation in the results of the diagonal and coupling terms for interaction coefficients. Finally, some conclusions are drawn on the basis of the present analysis.

scholarly journals Research on Coupled Dynamic Model of Tracked Vehicles and Its Solving Method

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Yuliang Li ◽  
Chong Tang
Keyword(s):  
Dynamic Performance ◽  
Tractive Force ◽  
Actual Structure ◽  
Discrete Method ◽  
Tracked Vehicles ◽  
Coupled Equations ◽  
Calculation Results ◽  
Dynamic Software ◽  
Multi Body ◽  
Body Dynamic

In order to conveniently analyze the dynamic performance of tracked vehicles, mathematic models are established based on the actual structure of vehicles and terrain mechanics when they are moving on the soft random terrain. A discrete method is adopted to solve the coupled equations to calculate the acceleration of the vehicle’s mass center and tractive force of driving sprocket. Computation results output by the model presented in this paper are compared with results given by the model, which has the same parameters, built in the multi-body dynamic software. It shows that the steady state calculation results are basically consistent, while the model presented in this paper is more convenient to be used in the optimization of structure parameters of tracked vehicles.

A numerical study of the sedimentation of fibre suspensions

1998 ◽  
Vol 376 ◽  
pp. 149-182 ◽  
Author(s):  
MICHAEL B. MACKAPLOW ◽  
ERIC S. G. SHAQFEH
Keyword(s):  
Monte Carlo ◽  
Steady State ◽  
Monte Carlo Simulations ◽  
Numerical Study ◽  
Point Particle ◽  
Hydrodynamic Interactions ◽  
Dynamic Simulations ◽  
Slender Body Theory ◽  
Fibre Suspensions ◽  
The Mean

The sedimentation of fibre suspensions at low Reynolds number is studied using two different, but complementary, numerical simulation methods: (1) Monte Carlo simulations, which consider interparticle hydrodynamic interactions at all orders within the slender-body theory approximation (Mackaplow & Shaqfeh 1996), and (ii) dynamic simulations, which consider point–particle interactions and are accurate for suspension concentrations of nl3=1, where n and l are the number density and characteristic half-length of the fibres, respectively. For homogeneous, isotropic suspensions, the Monte Carlo simulations show that the hindrance of the mean sedimentation speed is linear in particle concentration up to at least nl3=7. The speed is well predicted by a new dilute theory that includes the effect of two-body interactions. Our dynamic simulations of dilute suspensions, however, show that interfibre hydrodynamic interactions cause the spatial and orientational distributions to become inhomogeneous and anisotropic. Most of the fibres migrate into narrow streamers aligned in the direction of gravity. This drives a downward convective flow within the streamers which serves to increase the mean fibre sedimentation speed. A steady-state orientation distribution develops which strongly favours fibre alignment with gravity. Although the distribution reaches a steady state, individual fibres continue to rotate in a manner that can be qualitatively described as a flipping between the two orientations aligned with gravity. The simulation results are in good agreement with published experimental data.

Reduced-Order Time-Domain Simulation of Floating Bodies for Efficient Design Analysis

2015 ◽  
Author(s):  
Hyun Y. Kim ◽  
Stephanie L. Fitzpatrick ◽  
David C. Kring
Keyword(s):  
Memory Function ◽  
Computational Effort ◽  
Impulse Response Functions ◽  
Time Domain Simulation ◽  
Efficient Design ◽  
Floating Bodies ◽  
Order Model ◽  
Reduced Order ◽  
Multi Body ◽  
Multiple Floating Bodies

This paper describes the development and implementation of a reduced-order model to represent the hydrodynamic forces acting on a ship using Impulse-Response Functions (IRF). The approach will be conducted using Aegir, a timedomain seakeeping program that uses an advanced, Non-Rational Uniform B-Spline (NURBS) based, high-order boundary element method. The Cummins equation is slightly modified such that the memory function is decomposed into two terms: one for the impulsive velocity and the other term for the impulsive displacement. The present approach also further develops a method to simulate interactions between multiple floating bodies. The IRF convolutions for the free surface memory effect significantly reduce the computational effort compared to direct simulation. This will be demonstrated for both single and multi-body forward-speed, seakeeping simulations.

Numerical Study on Hydrodynamic Responses of a Two-Body System in Side-by-Side Operation

2016 ◽  
Author(s):  
Shaowu Ou ◽  
Shixiao Fu ◽  
Wei Wei ◽  
Tao Peng ◽  
Xuefeng Wang
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Optimal Operation ◽  
Hydrodynamic Interactions ◽  
Irregular Waves ◽  
Mooring System ◽  
Time Varying ◽  
Body System ◽  
The Time Domain ◽  
Two Bodies

Typically, in some side-by-side offshore operations, the speed of vessels is very low or even 0 and the headings are manually maneuvered. In this paper, the hydrodynamic responses of a two-body system in such operations under irregular seas are investigated. The numerical model includes two identical PSVs (Platform Supply Vessel) as well as the fenders and connection lines between them. A horizontal mooring system constraining the low frequency motions is set on one of the ships to simulate maneuver system. Accounting for the hydrodynamic interactions between two bodies, 3D potential theory is applied for the analysis of their hydrodynamic coefficients. With wind and current effects included, these coefficients are further applied in the time domain simulations in irregular waves. The relevant coefficients are estimated by experiential formulas. Time-varying loads on fenders and connection lines are analyzed. Meanwhile, the relative motions as well as the effects of the hydrodynamic interactions between ships are further discussed, and finally an optimal operation scheme in which operation can be safely performed is summarized.

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