A Study of Dynamic Responses and Wave Loads on Ships by 3-D Green Function Method

2006 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Green Function ◽  
Design Procedure ◽  
Ship Design ◽  
Dynamic Responses ◽  
Ship Motions ◽  
Wave Loads ◽  
Forward Speed ◽  
Regular Waves ◽  
Field Problem ◽  
Dynamic Wave

The dynamic wave loads are the most significant factor for the hull design of a ship. But experimental works for the motion responses of a ship and sea loads on her are expensive and time consuming for individual ship design. Therefore, the development of theoretical and numerical methods for predicting ship motions and dynamic loads on a ship in waves is very important for rational ship design procedure. In general, though 3-D Green function techniques with forward speed need long computation time, however it should be more accurate assumption of the flow field problem on an advancing ship in waves. Nowadays the availability of much faster computer makes the 3-D Green function techniques with forward speed more familiar than before. In this paper, numerical analyses on ship motions and wave loads are presented for ships with forward speed advancing in regular waves. 3-D Green function techniques have been used to carry out the numerical computations for the radiation problem and wave loads for a moving ship. Based on the 3–D linearized potential theory, dynamic wave loads have been computed of a bulk carrier in regular waves where experimental measurements are available. The computations are carried out for various heading angles between head sea and following sea and various ranges of frequencies. The results for motions, and vertical and horizontal bending moments are presented in this paper. Computed results are compared with the experimental data. The results calculated by the present method are found in fairly good agreement with the experimental results and those calculated by the other researchers. Using developed computer code, some parametric studies are also carried out for the ship design criteria and the discussions are made.

SHIP MOTIONS DURING REPLENISHMENT AT SEA OPERATIONS IN HEAD SEAS

2021 ◽  
Vol 152 (A4) ◽  
Author(s):  
G Thomas ◽  
T Turner ◽  
T Andrewartha ◽  
B Morris
Keyword(s):  
Experimental Study ◽  
Green Function ◽  
Prediction Method ◽  
Ship Motion ◽  
Motion Prediction ◽  
Ship Motions ◽  
Forward Speed ◽  
Theoretical Predictions ◽  
Relative Separation ◽  
Replenishment At Sea

During replenishment at sea operations the interaction between the two vessels travelling side by side can cause significant motions in the smaller vessel and affect the relative separation between their replenishment points. A study into these motions has been conducted including theoretical predictions and model experiments. The model tests investigated the influence of supply ship displacement and longitudinal separation on the ships’ motions. The data obtained from the experimental study has been used to validate a theoretical ship motion prediction method based on a 3-D zero-speed Green function with a forward speed correction in the frequency domain. The results were also used to estimate the expected extreme roll angle of the receiving vessel, and the relative motion between the vessels, during replenishment at sea operations in a typical irregular seaway. A significant increase in the frigate’s roll response was found to occur with an increase of the supply ship displacement, whilst a reduction in motion for the receiving vessel resulted from an increase in longitudinal separation between the vessels. It is proposed that to determine the optimal vessel separation it is vital that the motions of the vessels are not considered in isolation and all motions need to be considered for both vessels simultaneously.

Experimental and Numerical Investigation of the Wave-Induced Loads on a Deep-V Catamaran in Regular Waves

2013 ◽  
Author(s):  
Musa B. Bashir ◽  
Longbin Tao ◽  
Mehmet Atlar ◽  
Robert S. Dow
Keyword(s):  
Wave Loads ◽  
Forward Speed ◽  
Regular Waves ◽  
Hull Form ◽  
Proper Understanding ◽  
Towing Tank ◽  
Centre Of Gravity ◽  
Numerical Predictions ◽  
New Research ◽  
Wave Induced

This paper presents the results of towing tank tests carried out to predict the wave loads in regular wave conditions on a Deep-V hull form catamaran model. The experiments were carried out at the Newcastle University towing tank using a segmented model of the university’s new research vessel, “The Princess Royal”. The vessel is a twin hull with a Deep-V shape cross-section. The model, divided into two parts at the cross-deck level, was fitted with a 5-axis load cell at the position of the vessel’s centre of gravity in order to measure the motions response and wave loads due to the encountered waves. The longitudinal, side and vertical forces, along with the prying and yaw splitting moments were measured. The results obtained were further compared with those from numerical predictions carried out using a 3D panel method code based on potential flow theory that uses Green’s Function with the forward speed correction in the frequency domain. The results highlight reasonable correlations between the measurements and the predictions as well as the need for a proper understanding of the response of the multihull vessels to the wave-induced loads due to the non-linearity that have been observed in the experimental measurements of wave loads.

Improving the Panel-Free Method for the Prediction of Ship Motions and Wave Induced Loads

2017 ◽  
Author(s):  
Wei Qiu ◽  
Heather Peng ◽  
Junshi Wang ◽  
Shahriar Nizam
Keyword(s):  
Simple Algorithm ◽  
Design Stage ◽  
Ship Motions ◽  
Wave Loads ◽  
Forward Speed ◽  
Early Design Stage ◽  
B Splines ◽  
Frequency Domain Methods ◽  
Nurbs Surfaces ◽  
Wave Induced

Frequency-domain methods are proven efficient and reliable, especially for zero forward speed, in early design stage for the prediction of ship motions and wave-induced wave loads. There are still challenges for ships with forward-speed due to the inaccuracy in the computation of m-terms. In this paper, the panel-free method is further improved to predict motions and wave-induced loads on real ships with forward speeds. A simple algorithm has been developed to re-arrange the control points for Non-Uniform Rational B-Splines (NURBS) surfaces. This method led to reliable and accurate m-term computations and therefore improved ship motion and load predictions. Validation studies have been carried out for a hydroelastic model of a frigate. Computed motions and loads were compared with experimental data.

scholarly journals WAVE-INDUCED LOADS ON CROSS-DECK OF A WAVE-PIERCING TRIMARAN WITH DIFFERENT HULL FORMS OF OUTRIGGERS

Transport ◽  
2019 ◽  
Vol 34 (5) ◽  
pp. 559-568
Author(s):  
Abolfath Askarian Khoob ◽  
Mohammad Javad Ketabdari
Keyword(s):  
Potential Flow ◽  
Wave Loads ◽  
Forward Speed ◽  
Regular Waves ◽  
Hull Form ◽  
High Speeds ◽  
Complex Structural ◽  
Hull Forms ◽  
Wave Induced ◽  
Study Offer

Trimaran has unique hull form with a rapidly growth in recent years due to its application as a mode of transports and naval vessels. Designing trimaran faces many technical challenges because of its complex structural outlines and high-speeds operation. This article investigates the influence of side hulls configuration (symmetric, inboard and outboard types) for wave loads on cross-deck of a trimaran ship when advancing at sea in regular waves. The computation of these hydrodynamic forces is carried out using MAESTRO-Wave 3D panel method code. This code is based on potential flow theory that uses Green’s function with the forward speed correction in the frequency domain. The results demonstrate that the outboard side hull form has the best performance on wave-induced load among three kinds of side hull forms. Furthermore, the results of this study offer more information for selecting the side hull form of the trimaran.

Influence of the Waterline Integral on the Solution of the Frequency-Domain Forward-Speed Radiation-Diffraction Problem of a Ship Advancing in Waves

2014 ◽  
Author(s):  
D. C. Hong ◽  
S. Y. Hong ◽  
G. J. Lee ◽  
M. S. Shin
Keyword(s):  
Integral Equation ◽  
Free Surface ◽  
Green Function ◽  
Frequency Domain ◽  
Surface Condition ◽  
Numerical Results ◽  
Forward Speed ◽  
Line Integral ◽  
Free Surface Condition ◽  
Surface Green Function

The radiation-diffraction potential of a ship advancing in waves is studied using the three-dimensional frequency-domain forward-speed free-surface Green function (Brard 1948) and the forward-speed Green integral equation (Hong 2000). Numerical solutions are obtained by making use of a second-order inner collocation boundary element method which makes it possible to take account of the line integral along the waterline in a rigorous manner (Hong et al. 2008). The present forward-speed Green integral equation includes not only the usual free surface condition for the potential but also the adjoint free surface condition for the forward-speed free-surface Green function as indicated by Brard (1972). Comparison of the present numerical results of the heave-heave wave damping coefficients and the experimental results for the Wigley ship models I, II and III (Journee 1992) has been presented. These coefficients are compared with those calculated without taking into account of the line integral along the waterline in order to show the forward speed effect represented by the waterline integral when it is properly included in the free-surface Green integral equation. Comparison of the present numerical results and the equivalent time-domain results (Hong et al. 2013) has also been presented.

Springing Responses Analysis and Segmented Model Testing on a 550,000 DWT Ore Carrier

2016 ◽  
Author(s):  
Hui Li ◽  
Di Wang ◽  
Cheng Ming Zhou ◽  
Kaihong Zhang ◽  
Huilong Ren
Keyword(s):  
Natural Frequency ◽  
Design Stage ◽  
Resonant Vibration ◽  
Bending Moments ◽  
Wave Loads ◽  
Regular Waves ◽  
Segmented Model ◽  
Ship Model ◽  
Hull Structure ◽  
Stiffness Distribution

For ultra large ore carriers, springing response should be analyzed in the design stage since springing is the steady-state resonant vibration and has an important effect on the fatigue strength of hull structure. The springing response of a 550,000 DWT ultra large ore carrier has been studied by using experimental and numerical methods. A flexible ship model composed of nine segments was used in the experiment. The model segments were connected by a backbone with varying section, which can satisfy the request of natural frequency and stiffness distribution. The experiments in regular waves were performed and the motions and wave loads of the ship were measured. The experimental results showed that springing could be excited when the wave encounter frequency coincides with half or one-third the flexural natural frequency of the ship. In this paper, the analysis of the hydroelastic responses of the ultra large ore carrier was also carried out using a 3-D hydroelastic method. Comparisons between experimental and numerical results showed that the 3-D hydroelastic method could predict the motions and the vertical bending moments quite well. Based on this numerical method, the fatigue damage was estimated and the contribution of springing was analyzed.

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