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.

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.

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.

Time Domain Computation of the Wave-Making Resistance of Ships

2005 ◽  
Vol 49 (02) ◽  
pp. 144-158 ◽  
Author(s):  
F. Kara ◽  
D. Vassalos
Keyword(s):  
Steady State ◽  
Time Domain ◽  
Three Dimensional ◽  
Impulse Response Function ◽  
The Body ◽  
Source Distribution ◽  
Research Centre ◽  
Surface Source ◽  
Calm Water ◽  
Marine Engineering

The Ship Stability Research Centre, Department of Naval Architecture and Marine Engineering, The Universities of Glasgow and Strathclyde, Scotland, UKA linearized three-dimensional potential flow formulation in time domain is applied to calculate wave-making resistance of ships in calm water. Steady-state perturbation potentials for resistance are obtained as the steady-state limit of the surge radiation impulse response function using the transient free surface source distribution over the body surface. Five different vessels are used to validate the present numerical approximation. The results, including steady-state wave-making resistance, sinkage force, trim moment, and wave profile along the waterline, are compared with other published numerical and experimental results.

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.

Numerical Analysis of the Influence of Above-Water Bow Form on Added Resistance Using Nonlinear Slender Body Theory

2005 ◽  
Vol 49 (03) ◽  
pp. 191-206
Author(s):  
Hajime Kihara ◽  
Shigeru Naito ◽  
Makoto Sueyoshi
Keyword(s):  
Three Dimensional ◽  
Wave Force ◽  
Slender Body ◽  
Added Resistance ◽  
Slender Body Theory ◽  
Hull Form ◽  
Nonlinear Properties ◽  
Head Waves ◽  
The Time Domain ◽  
Body Theory

A nonlinear numerical method is presented for the prediction of the hydrodynamic forces that act on an oscillating ship with a forward speed in head waves. A "parabolic" approximation of equations called "2.5D" or "2D+T" theory was used in a three-dimensional ship wave problem, and the computation was carried out in the time domain. The nonlinear properties associated with the hydrostatic, hydrodynamic, and Froude-Krylov forces were taken into account in the framework of the slender body theory. This work is an extension of the previous work of Kihara and Naito (1998). The application of this approach to the unsteady wave-making problem of a ship with a real hull form is described. The focus is on the influence of the above-water hull form on the horizontal mean wave force. Comparison with experimental results demonstrates that the method is valid in predicting added resistance. Prediction of added resistance for blunt ships is also shown by example.

A Comparison of Two-Dimensional and Three-Dimensional Hydroelasticity Theories Including the Effect of Slamming

1991 ◽  
Vol 205 (1) ◽  
pp. 3-15 ◽  
Author(s):  
S Aksu ◽  
W G Price ◽  
P Temarel
Keyword(s):  
Steady State ◽  
Shear Force ◽  
Statistical Data ◽  
Three Dimensional ◽  
Bending Moment ◽  
Two Dimensional ◽  
Dimensional Theory ◽  
Flexible Bodies ◽  
Strip Theory ◽  
Head Waves

The behaviour of slender and non-slender flexible bodies travelling in irregular seaways is examined. This is achieved by using a two-dimensional (2D) and a three-dimensional (3D) theory. These theories are based on different assumptions and mathematical models, though both are capable of assessing the influence of transient loadings caused by slamming. The two-dimensional theory is restricted to steady state and transient vertical responses (motion, distortion, bending moment, shear force) in irregular head waves, whereas the three-dimensional theory allows calculations of both vertical responses and transverse responses (motion, distortion, bending moment, shear force, twist) in head and oblique waves. Time-domain simulations of the responses (steady state and transient) are generated from which statistical data are determined. For a slender uniform barge structure travelling in head seas, the response simulations and statistical data evaluated by the two theories show favourable agreement. However, for a non-slender uniform barge differences between predictions arise with the two-dimensional strip theory eventually failing, while the three-dimensional approach remains effective and its versatility is further demonstrated by predicting the slamming behaviour of a flexible barge structure travelling at arbitrary heading in an irregular seaway.

An Efficient Prediction Method for the Azimuthal Migration of Combustion Inhomogeneity in Multi-Stage Cooled Turbines

2021 ◽  
Author(s):  
Qingfu He ◽  
Zhongran Chi ◽  
Shusheng Zang
Keyword(s):  
Steady State ◽  
Working Conditions ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Prediction Method ◽  
Outlet Temperature ◽  
Multi Stage ◽  
Unsteady Simulation ◽  
Efficient Prediction ◽  
Turbine Exhaust

Abstract The outlet temperature of combustor is commonly monitored by thermocouples at the turbine exhaust. In order to establish the corresponding relationship between the temperature measured by each thermocouple and the working state of each burner, the azimuthal migration of the combustion hot/cold streaks in the multi-stage turbines needs to be quantified. Experiments to measure this migration have high cost and considerable error. It is also difficult to quantify the migration under multiple working conditions. Three-dimensional full-annulus unsteady simulation can obtain this migration. But the unsteady simulation of a single working condition could take several weeks, which is too expensive for engineering usage. A method named Steady-state Computation of Azimuthal Migration (SCAM) is proposed in this paper. By establishing and solving the transport equation of the migration angle, the azimuthal migration of hot/cold streaks can be predicted by steady-state numerical simulation using the mixing plane at rotor-stator interface. The migration computed by this method is compared with the full-annulus unsteady simulation results in multiple working conditions. The results of SCAM method show good agreement with full-annulus simulations, while costing only 0.01% of the CPU hours. It is also found that the error of SCAM is mainly caused by the fixed boundary value at coolant source terms. The optimal spanwise location of the thermocouples at turbine exhaust is discussed based on the results. The method proposed could be applied to the fault diagnosis and precise repair of the combustors of gas turbines.

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.

Shallow-Water Effect on the Motions of Three-Dimensional Bodies in Waves

1987 ◽  
Vol 31 (01) ◽  
pp. 34-40
Author(s):  
Hideichi Endo
Keyword(s):  
Green Function ◽  
Shallow Water ◽  
Three Dimensional ◽  
Source Distribution ◽  
Linear Wave ◽  
Water Effect ◽  
Surface Source ◽  
Distribution Method ◽  
The Green Function ◽  
Shallow Water Effect

The motions of three-dimensional bodies of arbitrary shape freely floating in waves in shallow water are studied. The wave loads on and hydrodynamic forces of a rigid body are calculated by applying the surface source distribution method (Green's function method) in the framework of linear wave potential theory. Special attention is paid to the numerical evaluation of the Green function for finite water depth; namely, an improper integral containing a singularity in the Green function is obtained by Gauss-Laguerre quadrature, and the ∫1 lr* ds term obtained is by numerical quadrature. Computational results of wave exciting forces, hydrodynamic coefficients, and motions of freely floating structures in shallow and deep water are compared with those obtained in the literature. Furthermore, the shallow-water effect on the motions of a large structure is examined.

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