scholarly journals Computation of ship responses in waves using panel method

1970 ◽  
Vol 1 (1) ◽  
pp. 35-46 ◽  
Author(s):  
MN Islam ◽  
MR Islam ◽  
MS Baree
Keyword(s):  
Green Function ◽  
Degrees Of Freedom ◽  
Velocity Potential ◽  
Panel Method ◽  
Numerical Code ◽  
Source Distribution ◽  
Forward Speed ◽  
Six Degrees Of Freedom ◽  
Marine Engineering ◽  
Speed Effect

Hydrodynamic coefficients, Forces / Moments and Motions of a ship moving with a mean forward speed in six degrees of freedom are computed using Panel Method. In this study, an existing numerical model without speed consideration was modified by incorporating the speed parameters. Appropriate Green function was used to calculate the concern velocity potential. The accuracy of the developed numerical code employing the Panel Method has been validated by comparing the result with known/published results of a series 60 ship available in the literature. Based on the results presented in the paper, it can be concluded that the developed model is able to predict the responses of the ship with forward speed effect. Keywords: Motions, Green function, 3D Source distribution.   doi: 10.3329/jname.v1i1.2037 Journal of Naval Architecture and Marine Engineering 1(2004) 35-46

On the Radiation and Diffraction of Surface Waves by Submerged Spheroids

1989 ◽  
Vol 33 (02) ◽  
pp. 84-92
Author(s):  
G. X. Wu ◽  
R. Eatock Taylor
Keyword(s):  
Degrees Of Freedom ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Added Mass ◽  
Wave Radiation ◽  
Legendre Functions ◽  
Incoming Wave ◽  
Six Degrees Of Freedom ◽  
Damping Coefficients ◽  
Exciting Forces

The problem of wave radiation and diffraction by submerged spheroids is analyzed using linearized three-dimensional potential-flow theory. The solution is obtained by expanding the velocity potential into a series of Legendre functions in a spheroidal coordinate system. Tabulated and graphical results are provided for added mass and damping coefficients of various spheroids undergoing motions in six degrees of freedom. Graphs are also provided for exciting forces and moments corresponding to a range of incoming wave angles.

scholarly journals Prediction of transient loading on a propeller from an approching ice block

1970 ◽  
Vol 2 (1) ◽  
pp. 15-20 ◽  
Author(s):  
P Liu ◽  
B Colbourne ◽  
Chin Shin
Keyword(s):  
Numerical Models ◽  
Panel Method ◽  
The Body ◽  
Source Distribution ◽  
Hydrodynamic Load ◽  
Surface Panel Method ◽  
Time Step ◽  
Suction Force ◽  
Propeller Blades ◽  
Marine Engineering

An unsteady 3D surface panel method has been developed to predict hydrodynamic load fluctuations on an ice class propeller induced by continuous variation of proximity to an ice block. The low order, time domain, combined doublet and source panel method approximates the doublet and source distribution uniformly over each panel on the propeller blades. For non-lifting bodies, i.e., the hub and ice block, only sources are distributed over the body surfaces. The simulation model is contrived in such a manner that the ice block and surrounding fluid remain stationary; and at each time step, the propeller rotates and advances forward in the inertial reference frame. This numerical model is validated with previous fixed-proximity experimental measurements and good agreement is obtained. Prediction of the fluctuating hydrodynamic load is carried out as a full dynamic interaction between the ice block and the propeller. Results for this study are compared with previous fixed-proximity numerical models and experiments. The new dynamic model establishes a basis for analysis of a more realistic fluid-structure interaction, which could, in the future, include ice block acceleration due to suction force and ice block impact loading on the propeller blade and shaft. Keywords: Marine Propulsion, Panel Methods, Unsteady Loading, Ice-Propeller Interaction doi: 10.3329/jname.v2i1.2026 Journal of Naval Architecture and Marine Engineering 2(1)(2005) 15-20

scholarly journals Prediction of Ship Unsteady Maneuvering in Calm Water by a Fully Nonlinear Ship Motion Model

2012 ◽  
Vol 2012 ◽  
pp. 1-11
Author(s):  
Ray-Qing Lin ◽  
Tim Smith ◽  
Michael Hughes
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Ship Motion ◽  
Ship Motions ◽  
Motion Model ◽  
Forward Speed ◽  
Fully Nonlinear ◽  
Six Degrees Of Freedom ◽  
Calm Water

This is the continuation of our research on development of a fully nonlinear, dynamically consistent, numerical ship motion model (DiSSEL). In this study we will report our results in predicting ship motions in unsteady maneuvering in calm water. During the unsteady maneuvering, both the rudder angle, and ship forward speed vary with time. Therefore, not only surge, sway, and yaw motions occur, but roll, pitch and heave motions will also occur even in calm water as heel, trim, and sinkage, respectively. When the rudder angles and ship forward speed vary rapidly with time, the six degrees-of-freedom ship motions and their interactions become strong. To accurately predict the six degrees-of-freedom ship motions in unsteady maneuvering, a universal method for arbitrary ship hull requires physics-based fully-nonlinear models for ship motion and for rudder forces and moments. The numerical simulations will be benchmarked by experimental data of the Pre-Contract DDG51 design and an Experimental Hull Form. The benchmarking shows a good agreement between numerical simulations by the enhancement DiSSEL and experimental data. No empirical parameterization is used, except for the influence of the propeller slipstream on the rudder, which is included using a flow acceleration factor.

A New Slender-Ship Theory Valid for all Oscillatory Frequencies and Forward Speeds

2013 ◽  
Author(s):  
Masashi Kashiwagi ◽  
Xin Wang
Keyword(s):  
Green Function ◽  
Present Theory ◽  
Added Mass ◽  
Source Distribution ◽  
Unified Theory ◽  
Forward Speed ◽  
Radiation Problem ◽  
Damping Coefficients ◽  
Radiation Wave ◽  
The Green Function

A new theory is presented for the radiation problem of heave and pitch of a slender ship advancing at arbitrary forward speed. The theory has no restriction on the order of forward speed and oscillation frequency. The general inner solution is constructed by the source distribution with Green function over the ship’s hull surface plus a line distribution along the ship’s centerline on the free surface with the radiation-wave related residue part of the Green function. By matching the inner solution with the outer solution, the source strengths on both hull surface and line distribution can be obtained. Numerical results of the added-mass and damping coefficients based on the present theory are shown for two modified Wigley models and compared with the unified theory and experiment results.

Effect of Wind Loads on the Performance of Free-Fall Lifeboats

2014 ◽  
Author(s):  
Thomas Sauder ◽  
Eloise Croonenborghs ◽  
Sebastien Fouques ◽  
Nabila Berchiche ◽  
Svein-Arne Reinholdtsen
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Free Fall ◽  
Offshore Structures ◽  
Water Entry ◽  
Forward Speed ◽  
Cfd Simulations ◽  
Six Degrees Of Freedom ◽  
Complete Set ◽  
Water Exit

The paper presents a model describing the launch of free-fall lifeboats from offshore structures in strong environmental wind. Six-degrees-of-freedom numerical simulations of the lifeboat launch are performed using the free-fall lifeboat simulator VARUNA with a complete set of wind coefficients for the lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry. It is shown by means of numerical simulations that wind-induced loads on the lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the lifeboat, and on its forward speed after water exit. It is concluded that the effect of wind-induced loads on the lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.

Prediction of Wave-Induced Motions and Loads of Ships With Forward Speed by Matching Method

2020 ◽  
Author(s):  
Hui Li ◽  
Baoli Deng ◽  
Chunlei Liu ◽  
Jian Zou ◽  
Huilong Ren
Keyword(s):  
Green Function ◽  
Exterior Domain ◽  
Boundary Integral ◽  
Control Surface ◽  
Source Distribution ◽  
Forward Speed ◽  
Matching Method ◽  
Distribution Method ◽  
Interior Domain ◽  
Wave Induced

Abstract A novel matching method has been developed to solve the wave-induced motions and loads of ships with forward speed. The fluid domain is divided into two subdomains by a cylindrical control surface: an interior domain and an exterior domain. Unlike the conventional domain decomposition strategy, the control surface is meshless in present method, on which the physical quantities are expanded into Fourier-Laguerre series. Based on forward speed Green function, the source distribution method is adopted to solve the exterior domain. The calculations of boundary integral equation about forward speed Green function over the control surface are performed analytically, and the solution of exterior domain provides a Dirichlet-to-Neumann (DN) relation on the control surface. In the interior domain, the boundary value problem is solved by Rankine source method. In order to be consistent with exterior solution, the control surface is kept meshless. The ship hull is discretized into constant panels. The free-surface is discretized into cubic B-splines to represent the high-order derivatives of velocity potential precisely. Then, the DN relation is used to close the equation system established in the interior domain. Comparisons with known experimental measurements show that the calculations achieve good accuracy. Furthermore, the influences of numerical method used in the exterior domain are described.

scholarly journals Motion Simulation of a Fine Shaped Vessel at Hiron Point in the Bay of Bengal

1970 ◽  
Vol 2 (2) ◽  
pp. 25-40
Author(s):  
M Rafiqul Islam ◽  
Md Munir Hassan ◽  
Md Sdaiqul Baree
Keyword(s):  
Mathematical Model ◽  
Bay Of Bengal ◽  
Wave Spectrum ◽  
Research Work ◽  
Irregular Waves ◽  
Source Distribution ◽  
Forward Speed ◽  
Distribution Method ◽  
Hydrodynamic Behaviour ◽  
Speed Effect

The hydrodynamic behaviour of a fast fine vessel is of great importance than that of a fuller vessel as the fast fine vessels are engaged for important operations. Moreover with the advent of modern computers, in ship hydrodynamics, 3-D source distribution method is gaining much popularity and normally applied for blocky hull. But in the case of finer hull, examples are rare especially considering forward speed effect. With these views in mind, in the present research work, effort has been given to develop a mathematical model for fine shape vessel to predict and simulate her motions in irregular waves. A computer program has been developed on the basis of mathematical model and to examine the validity of the developed program, results for hydrodynamic coefficient and motions of a series 60 ship have been compared with Gerristma's experimental results and with the results based on other codes. After validation of the program, simulation of motions of an existing the fine shape ship has been carried out at Hiron point of the Bay of Bengal by utilizing hydrodynamic coefficients and wave exciting forces and moments obtained in regular waves and a new wave spectrum formula based on wave data at the concerned location. On the basis of the results presented, it may be concluded that the developed model based on 3-D distribution technique can be applied for prediction of motion of fine shape ship with forward speed effect. Moreover limitations of operation of the vessel have been demonstrated at various combinations of significant wave heights and speeds. doi:10.3329/jname.v2i2.1870  Journal of Naval Architecture and Marine Engineering 2(2005) 25-40

A Numerical Calculation of Hydrodynamic Forces on a Seagoing Ship by 3-D Source Technique With Forward Speed

2004 ◽  
Author(s):  
Yoshiyiki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Free Surface ◽  
Velocity Potential ◽  
Hydrodynamic Forces ◽  
The Body ◽  
Source Distribution ◽  
Accurate Estimation ◽  
Forward Speed ◽  
Surface Ship ◽  
Wave Patterns ◽  
Wigley Hull

In this paper, the hydrodynamic forces of a surface ship advancing in waves at constant forward speed are numerically calculated by using the 3-D source distribution techniques. The paper also deals with the numerical calculations of free surface flow around an advancing ship in calm water as well as in waves. The body boundary condition is linearised about the undisturbed position of the body and the free surface condition is linearised about the mean water surface. The potential is represented by a distribution of sources over the surface of the ship and its waterline. The problem is solved by the method of singularities distributed over the hull surface. Hess & Smith method is used to obtain the density of these singularities. The numerical solution of the surface ship case is approximately obtained by considering the hull as a position of plane polygonal elements, bearing a constant singularity distribution. The velocity potential of any particular point in the free surface around the moving hull is determined by using the 3-D Green function with forward speed which satisfies the boundary conditions for a pulsating source in the fluid. Contours of wave patterns around moving surface ships are calculated from the velocity potential. The numerical accuracy of the computer code is firstly checked by calculating the velocity potential of a translating, pulsating unit source with arbitrary frequency and forward speed. Free surface wave patterns generated by a Wigley hull advancing with steady forward speed are calculated by using this code. Some corresponding hydrodynamic coefficients of heave and pitch modes for the Wigley hull has been calculated. Exciting forces and motion amplitudes are also investigated. The numerical result of this code is validated by comparing the calculated results with the experimental ones and those calculated by other methods. From the comparison, the results predicted by the present calculations are found in fairly good agreement with the experiment. Finally, the effects of motion amplitude on the free surface elevation are analyzed. These will be helpful for the accurate estimation of sea keeping problems for a ship advancing in waves.

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