Calculation and Analysis of Components of Added Resistance of Ships in Waves

2015 ◽  
Author(s):  
Hong Liang ◽  
Zhu Chuan ◽  
Miao Ping
Keyword(s):  
Frequency Domain ◽  
Present Method ◽  
Three Dimensional ◽  
Wave Resistance ◽  
Source Distribution ◽  
Ship Motions ◽  
Hydrodynamic Coefficients ◽  
Added Resistance ◽  
Distribution Method ◽  
Different Types

Ship motions and its hydrodynamic coefficients are solved by three dimensional frequency domain potential theories with a translating and pulsating source distribution method. Furthermore, components of added wave resistance of ships advancing in waves due to the radiation and diffraction waves are obtained respectively. Added wave resistances of Wigley III hull and S175 containership with various forward speeds are carried out and analyzed in frequency domain. The numerical results are validated for the models by comparing them with experimental data. Its percentage of components of the total ship added wave resistance varying with frequency is investigated and discussed. The present method provides a rapid and efficient approach to predict added resistance of different types of ships in waves.

The Effect of the Steady Flow Potential on the Motions of a Moving Ship in Waves

2000 ◽  
Vol 44 (01) ◽  
pp. 14-32
Author(s):  
Ming-Chung Fang
Keyword(s):  
Steady Flow ◽  
Present Method ◽  
Three Dimensional ◽  
Source Distribution ◽  
Series Expansions ◽  
Ship Motions ◽  
Double Integral ◽  
Flow Potential ◽  
Principal Value ◽  
Good Agreement

A three-dimensional method to analyze the motions of a ship running in waves is presented, including the effects of the steady-flow potential. Basically, the general formulations are based on the source distribution technique by which the ship hull surface is regarded as the assembly of many panels. The present study includes three algorithms for treating the corresponding Green function:the Hess & Smith algorithm for the part of simple source I/r,the complex plane contour integral of the Shen & Farell algorithm for the double integral of steady flow, andthe series expansions of the Telste & Noblesse algorithm for the Cauchy principal value integral of unsteady flow. The study reveals that the effect of steady flow on ship motions is generally small, but it still cannot be neglected in some cases, especially for the ship running in oblique waves. The effect also depends on the fore-aft configuration of the ship. The results predicted by the present method are found to be in fairly good agreement with existing experiments and other theories.

The Prediction of the Added Resistance for the Trimaran Ship With Different Side Hull Arrangements in Waves

2009 ◽  
Vol 53 (04) ◽  
pp. 227-235
Author(s):  
Ming-Chung Fang ◽  
Yi-Chin Wu ◽  
Deng-Kai Hu ◽  
Zi-Yi Lee
Keyword(s):  
Steady State ◽  
Steady Flow ◽  
Three Dimensional ◽  
Prediction Method ◽  
Source Distribution ◽  
Added Resistance ◽  
Distribution Method ◽  
Related Data ◽  
Head Waves ◽  
Flow Potential

In this paper, a second-order steady-state approach and a three-dimensional pulsating source distribution method are applied to derive the added resistance on a trimaran ship advancing in waves. The added resistance treated here is the secondorder steady-state hydrodynamic force, which can be expressed as products of the ship-motion responses, the radiation potential, diffraction potential, and the incident wave potential, and all related velocity potentials are in three-dimensional form. The steady flow potential is also included in the motion response calculation to investigate its effect on the added resistance. In order to validate the prediction method, the experiments for measuring the added resistance of a trimaran model in head waves were also handled in a National Cheng Kung University (NCKU) towing tank, and the related data are adopted to compare with the theoretical results. The comparisons show that the prediction results obtained in the paper generally agree well with experimental data; the validity of the prediction method applied here can be regarded as acceptable, and the effect of the steady flow potential on the added resistance of the trimaran ship can be neglected.

Computation of Motion and Added Wave Resistance With the Panel-Free Method

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Hongxuan (Heather) Peng ◽  
Wei Qiu
Keyword(s):  
Experimental Data ◽  
Frequency Domain ◽  
Wave Resistance ◽  
Green Functions ◽  
Hydrodynamic Coefficients ◽  
Forward Speed ◽  
Wigley Hull

Computations have been performed to predict motions and added wave resistances for ships at forward speeds. The radiation and diffraction problems of a ship with forward speed are solved with the panel-free method in the frequency domain. In this paper, the effect of the m-terms and forward-speed/zero-speed Green functions (GFs) on the solutions are investigated using two Wigley hull ships. Computed motions, hydrodynamic coefficients, and added wave resistances were compared with the experimental data.

Study on the Motions and Stress of Immersing Tunnel Element under Wave Actions

2013 ◽  
Vol 328 ◽  
pp. 614-622
Author(s):  
Hong Da Shi ◽  
Shui Yu Li ◽  
Dong Wang
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Diffraction Theory ◽  
Wave Force ◽  
Source Distribution ◽  
Wave Forces ◽  
Linear Wave ◽  
Wave Loads ◽  
Distribution Method ◽  
Motion Responses

The dynamic characteristics of large-scale tunnel element are very important for the process of immersion. In the paper, the motions and stress of the element under wave actions were studied. The linear wave diffraction theory and the three-dimensional source distribution method were applied to calculate the wave loads and motion responses of the tunnel element under different incident wave conditions. In the study, there have no cable on the element. On the basis of the above theories, the stress and the motions of the element were studied. The first order wave forces and the second order wave force were deduced, and the motions equation was made.

Developments in the calculation of the wavemaking resistance of ships

1988 ◽  
Vol 416 (1850) ◽  
pp. 115-147 ◽  
Keyword(s):  
Three Dimensional ◽  
Source Distribution ◽  
Rectilinear Motion ◽  
Kelvin Wave ◽  
Distribution Method ◽  
Wave Source ◽  
Qualitative And Quantitative ◽  
Theoretical Predictions ◽  
Computational Aspects ◽  
Quantitative Manner

The wavemaking resistance of a rigid ship in steady rectilinear motion at the free surface of a previously calm ocean is evaluated by means of a linearized three-dimensional potential-flow formulation. Solutions to the disturbance potential of the steady perturbed flow about the moving ship are obtained by means of a Kelvin wave source distribution method. Particular emphasis is placed on computational aspects and accurate and efficient algorithms for the evaluation of the fundamental Kelvin wave source potential function are discussed. To illustrate the proposed method, experimental and theoretical predictions are compared for a variety of ship forms. In general, this approach shows the correct behaviour of the variation of the wavemaking resistance with forward speed in both a qualitative and quantitative manner.

scholarly journals Salvesen’s Method for Added Resistance Revisited

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Mostafa Amini-Afshar
Keyword(s):  
Direct Calculation ◽  
Wave Resistance ◽  
The Body ◽  
Ship Motions ◽  
Exact Equation ◽  
Added Resistance ◽  
Scattering Problems ◽  
Correct Treatment ◽  
Long Wave ◽  
Strip Theory

Abstract Almost 4 years after the appearance of Salvesen–Tuck–Faltinsen (STF) strip theory (Salvesen et al., 1970, “Ship Motions and Sea Loads,” Annual Meeting of the Society of Naval Architecture and Marine Engineers (SNAME), New York, Nov. 12–13), Salvesen in 1974 published his popular method for calculation of added resistance (Salvesen, 1974, “Second-Order Steady State Forces and Moments on Surface Ships in Oblique Regular Waves,” Vol. 22; Salvesen, 1978, “Added Resistance of Ships in Waves,” J. Hydronautics, 12(1), pp. 24–34). His method is based on an exact near-field formulation; however, he applied the long-wave and the weak-scatterer assumptions to present his approximate method using the integrated quantities (hydrodynamic and geometrical coefficients). Considering the available computational powers in the 1970s, both of these assumptions were absolutely justifiable. The intention of this paper is to disseminate the results of a recent study at the Technical University of Denmark, whereby the Salvesen’s formulation has been revisited and the added resistance is computed from the original exact equation without invoking the weak-scatterer or the long-wave assumptions. This is performed using the solutions of the radiation and the scattering problems, obtained by a low-order boundary element method and the two-dimensional free-surface Green function inside our in-house STF theory implementation (Bingham and Amini-Afshar, 2020, DTU_Strip Theory Solver). The weak-scatterer assumption is then removed through a direct calculation of the x-derivatives of the velocity potentials and the normal vectors along the body. Knowing the velocity potentials over each panel, the long-wave assumption is also avoided by a piece-wise analytical integration of sectional Kochin Function (Kochin, 1936, “On the Wave Resistance and Lift of Bodies Submerged in Fluid,” Transactions of the Conference on the Theory of Wave Resistance, Moscow.). The presented results for five ship geometries testify that the correct treatment of the original equation is achieved only after both of the above-mentioned assumptions are removed. Implemented in this manner, Salvesen’s method proves to be relatively more accurate and robust than has been generally perceived during all these years.

Wave Exciting Forces of a Free Floating Semi Submersible in Regular Waves

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
Hassan Abyn ◽  
Mohammad Rafiqul Islam ◽  
Jaswar Jaswar ◽  
Amin Mahmoudi ◽  
C. L. Siow ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Offshore Structures ◽  
Source Distribution ◽  
Linear Wave ◽  
Distribution Method ◽  
Exciting Forces ◽  
Domain Models ◽  
Wave Exciting Forces

Drilling and production of oil by semi submersible take place in many locations throughout the world. Generally, floating structures play an important role in exploring the oil and gas from the sea. The force and motion prediction of offshore structures may be carried out using time domain or frequency domain models or model tests. In this paper the frequency domain analysis used because it is the simplified and linearized form of the equations of motion. The time domain analysis, unlike frequency domain models, is adequate to deal with non-linearities such as viscous damping and mooring forces, but it requires sophisticated solution techniques and it is expensive to employ. In this paper, the wave exciting forces of a free floating semi-submersible were carried out using 3D source distribution method within the scope of the linear wave theory. The results obtained from computations were also compared with the results obtained using commercial software MOSES and WAMIT.  

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.

Numerical Study on Added Resistance Computations in Short Waves

2016 ◽  
Author(s):  
Xinshu Zhang ◽  
Kang Tian ◽  
Yunxiang You
Keyword(s):  
Experimental Data ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Three Dimensional ◽  
Added Resistance ◽  
Rankine Panel Method ◽  
Short Waves ◽  
Global Performance ◽  
Different Types ◽  
Wigley Hull

Evaluation of added resistance in short waves is critical to the assessment of the global performance of a ship traveling in a seaway. In this paper, three methods of added resistance evaluation in short waves are briefly reviewed, including those proposed by Fujii & Takahashi [1], Faltinsen et al. [2], and Kuroda et al. [3]. Based on the experimental data collected by Kuroda et al., a new method is developed for the estimation of added resistance in short waves. The proposed method is validated by comparing the obtained numerical results with experimental data and other numerical solutions for different types of hulls, including the Wigley hull I, KVLCC2 hull, Series 60 hull with CB = 0.7, and the S-175 hull. The present study confirms that the developed method can well predict the added resistance in short waves and complement the three-dimensional Rankine panel method developed in a previous study focusing on intermediate and long waves.

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