Numerical Investigation Into Uncertainty of Wave-Induced Vibration of Large Container Ships due to Ship Operation

2017 ◽  
Author(s):  
Kazuhiro Iijima ◽  
Rika Ueda ◽  
Masahiko Fujikubo
Keyword(s):  
Time Series ◽  
Bending Moment ◽  
Forward Speed ◽  
Sea State ◽  
Large Container ◽  
Hydroelastic Response ◽  
Wave Induced ◽  
Ship Operation ◽  
Vertical Bending Moment ◽  
Ship Speed

A series of seakeeping simulations accounting for the wave-induced vibration is performed on three large container ships with different sizes. Time series of bodily motions, accelerations and stress due to vertical bending moment are calculated for the three ships navigating in a short-term sea state. Ship forward speed is varied from 0 knot to 20knots to investigate the sensitivity of the hydroelastic response to the change of the speed. Statistical analysis is made over the time series results, and the results are compared in terms of significant value. The uncertainty of the wave-induced vibration with respect to the ship speed is evaluated for the respective ships. It is found out that the increase rate of pitch motion, accelerations and stress to the increase of the ships’ forward speed is different from each other. It is further observed that the acceleration and vertical bending moment increase is less prominent for the largest ship.

Load Combination for Fatigue Analysis of Ship Structures

2004 ◽  
Author(s):  
Yung S. Shin ◽  
Booki Kim ◽  
Alexander J. Fyfe
Keyword(s):  
Bending Moment ◽  
Linear Summation ◽  
Load Combination ◽  
Longitudinal Stiffeners ◽  
Stress Components ◽  
Tank Pressure ◽  
Wave Induced ◽  
Vertical Bending Moment ◽  
Oil Tanker

A methodology for calculating the correlation factors to combine the long-term dynamic stress components of ship structure from various loads in seas is presented. The methodology is based on a theory of a stationary ergodic narrow-banded Gaussian process. The total combined stress in short-tem sea states is expressed by linear summation of the component stresses with the corresponding combination factors. This expression is proven to be mathematically exact when applied to a single random sea. The long-term total stress is similarly expressed by linear summation of component stresses with appropriate combination factors. The stress components considered here are due to wave-induced vertical bending moment, wave-induced horizontal bending moment, external wave pressure and internal tank pressure. For application, the stress combination factors are calculated for longitudinal stiffeners in cargo and ballast tanks of a crude oil tanker at midship section. It is found that the combination factors strongly depend on wave heading and period in the short-term sea states. It is also found that the combination factors are not sensitive to the selected probability of exceedance level of the stress in the long-term sense.

Response Based Identification of Critical Wave Scenarios

2012 ◽  
Author(s):  
Günther F. Clauss ◽  
Marco Klein ◽  
Carlos Guedes Soares ◽  
Nuno Fonseca
Keyword(s):  
Linear Method ◽  
Bending Moment ◽  
Extreme Wave ◽  
Offshore Structure ◽  
Sea State ◽  
Worst Case ◽  
Strip Theory ◽  
Wave Conditions ◽  
Vertical Bending Moment ◽  
Method Approach

In the last years the identification and investigation of critical wave sequences regarding offshore structure responses became one of the main topics in the ocean engineering community. Thereby the area of interest covers the entire field of application spectra at sea — from efficient and economic offshore operations in moderate sea states to reliability as well as survival in extreme wave conditions. For most cases, the focus lies on limiting criteria for the design, such as maximum global loads, maximum relative motions between two or more vessels or maximum accelerations, at which the floating structure has to operate or to survive. These criteria are typically combined with a limiting characteristic sea state (Hs, Tp) or a rogue wave. For the investigation of offshore structures as well as the identification of critical wave sequences, different approaches are available — most of them are based on linear transfer functions as it is an efficient procedure for the fast holistic evaluation. But, for some cases the linear method approach implies uncertainties due to nonlinear response behavior, in particular in extreme wave conditions. This paper presents an approach to these challenges, a response based optimization tool for critical wave sequence detection. This tool, which has been successfully introduced for the evaluation of the applicability of a multi-body system based on the linear method approach, is adjusted to a nonlinear task — the vertical bending moment of a chemical tanker in extreme wave conditions. Therefore a nonlinear strip theory solver is introduced into the optimization routine to capture the nonlinear effects on the vertical bending moment due to steep waves acting on large bow flares. The goal of the procedure is to find a worst case wave sequence for a certain critical sea state. This includes intensive numerical investigation as well as model test validation.

Effects of Weather Routing on Maximum Vertical Bending Moment in a Ship Taking Account of Wave-Induced Vibrations

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Kazuhiro Iijima ◽  
Rika Ueda ◽  
Hitoi Tamaru ◽  
Masahiko Fujikubo
Keyword(s):  
North Atlantic Ocean ◽  
Meteorological Data ◽  
Bending Moment ◽  
Simulation Method ◽  
Extreme Value ◽  
Operational Parameters ◽  
Wave Condition ◽  
Weather Routing ◽  
Wave Induced ◽  
Vertical Bending Moment

In this paper, the effect of weather routing and ship operations on the extreme vertical bending moment (VBM) in a 6000TEU class large container ship which is operated in North Atlantic Ocean is addressed. A direct time-domain nonlinear response simulation method taking account of the wave-induced vibrations is combined with a voyage simulation based on 10 years of meteorological data in the area. The probability distribution of the ship's operational parameters conditional upon the meteorological conditions is considered. It is clarified that the most severe wave condition with the significant wave height over 16 m in the area may not be encountered by the ship due to the weather routing and the extreme value is determined mostly by the wave condition much milder than the most severe in the area. It is also found out that the ship speed assumed in the most contributing sea state strongly affects the extreme value of the total VBM. It is explained by the fact that the wave-induced vibrations in the ship tend to be excited at faster speed.

Steep Wave Effects on Wave Induced Vertical Bending Moment Using a 3D Numerical Wave Tank

2017 ◽  
Author(s):  
Shivaji Ganesan Thirunaavukarasu ◽  
Debabrata Sen ◽  
Yogendra Parihar
Keyword(s):  
Comparative Study ◽  
Incident Wave ◽  
Bending Moment ◽  
Wave Steepness ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Strip Theory ◽  
Numerical Wave ◽  
Wave Induced ◽  
Vertical Bending Moment

This paper presents a detail comparative study on wave induced vertical bending moment (VBM) between linear and approximate nonlinear calculations using a 3D numerical wave tank (NWT) method. The developed numerical approach is in time domain where the ambient incident waves can be defined by any suitable wave theory. Certain justifying approximations employed in the solution of the interaction hydrodynamics (diffraction and radiation) enabling the NWT to generate stable long duration time histories of all parameters of interest. This is an extension of our earlier works towards the development of a practical NWT based solution for wave-structure interactions [1]. After a brief outline of the implemented numerical details, a comprehensive validation and verification of vertical shear force (VSF) and bending moment RAOs computed using the linearized version of the NWT against the usual linear results of strip theory and 3D panel codes are presented. Next we undertake the comparative study between the fully linear and approximate nonlinear versions of the present code for different incident wave steepness. In the approximate nonlinear formulation, the ambient incident wave is defined by the full nonlinear numerical wave model based on Fourier approximation method which can generate very steep steady periodic nonlinear waves up to the near wave breaking limit. The nonlinearities associated with the incident Froude Krylov and hydrostatic restoring forces/moments are exact up to the instantaneous wetted surface at the displaced location, but the hydrodynamic diffraction and radiation effects are linearized around the mean wetted surface. The standard S175 container hull is considered for the comparative studies because of its geometric nonlinearities. Numerical simulations are performed for four different wave lengths with increasing wave steepness. It is observed that the computed wave induced VBM amidships from the approximate nonlinear results can be almost 30% higher compared to the results from a purely linear solution, which can be a critical issue from the safety point. Significant higher harmonics are also observed in the approximate nonlinear results which at some times may be responsible for exciting the undesirable whipping/springing responses.

Influence of Whipping on Long-term Vertical Bending Moment

2004 ◽  
Vol 48 (04) ◽  
pp. 261-272
Author(s):  
Gro Sagli Baarholm ◽  
Jørgen Juncher Jensen
Keyword(s):  
Nonlinear Response ◽  
Extreme Values ◽  
Bending Moment ◽  
Sea Waves ◽  
Short Term ◽  
Strip Theory ◽  
Long Time ◽  
Wave Induced ◽  
Vertical Bending Moment

This paper is concerned with estimating the response value corresponding to a long return period, say 20 years. Time domain simulation is required to obtain the nonlinear response, and long time series are required to limit the statistical uncertainty in the simulations. It is crucial to introduce ways to improve the efficiency in the calculation. A method to determine the long-term extremes by considering only a few short-term sea states is applied. Long-term extreme values are estimated using a set of sea states that have a certain probability of occurrence, known as the contour line approach. Effect of whipping is included by assuming that the whipping and wave-induced responses are independent, but the effect of correlation of the long-term extreme value is also studied. Numerical calculations are performed using a nonlinear, hydroelastic strip theory as suggested by Xia et al (1998). Results are presented for the S-175 containership (ITTC 1983) in head sea waves. The analysis shows that whipping increases the vertical bending moment and that the correlation is significant.

Effect of Heavy Weather Maneuvering on the Wave-Induced Vertical Bending Moments in Ship Structures

1990 ◽  
Vol 34 (01) ◽  
pp. 60-68 ◽  
Author(s):  
C. Guedes Soares
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Decision Rules ◽  
Bending Moment ◽  
Ship Motions ◽  
Bending Moments ◽  
Significant Wave ◽  
Course Changes ◽  
Wave Induced ◽  
Vertical Bending Moment

Statistical data are collected so as to quantify the probability of occurrence of voluntary course changes in heavy weather as well as their dependence on significant wave height and on ship heading. Decision rules are established about when and how to change course, on the basis of the analysis of operational data and of interviews with experienced shipmasters. A Monte Carlo simulation is performed so as to determine how an omnidirectional distribution of initial headings is changed by voluntary course changes depending on the significant wave height. Finally, the effect of the nonuniform distribution of headings on the mean wave-induced vertical bending moment is calculated. It is shown that although heavy weather maneuvering eases the ship motions, it can increase the wave-induced bending moments and thus increase the probability of structural failure.

Influence of Surge on Extreme Roll Amplitudes

2008 ◽  
Author(s):  
Jelena Vidic-Perunovic ◽  
Olav Rognebakke ◽  
Jo̸rgen Juncher Jensen ◽  
Preben Terndrup Pedersen
Keyword(s):  
Vertical Motion ◽  
Wave Crest ◽  
Forward Speed ◽  
Added Resistance ◽  
Pressure Force ◽  
Parametric Roll ◽  
Resonant Condition ◽  
Speed Variation ◽  
Wave Induced ◽  
Ship Speed

Interference of the wave-induced ship surge motion with roll dynamics has been studied. The surge motion has been included in a previously derived hydrodynamic roll prediction model in order to account for the ship speed variation due to the longitudinal incident wave pressure force. Depending on the position of the wave crest relatively to the ship, the ship will be slowed down when she meets the wave. In this paper attempts are made to accurately account for added resistance and additional thrust, applied in order to maintain the ship speed. The surge equilibrium equation has been longitudinally balanced in order to determine the added thrust term that would represent actions to maintain speed The resulting forward speed variation affects the frequency of encounter and the parametric roll resonant condition is directly influenced by this speed variation. The analysis procedure is demonstrated for an example containership sailing mainly in head sea condition and higher sea states. Sensitivity of the results to the added thrust model and vertical motion calculation is discussed.

Examination of Effect of Lateral Loads on the Hull Girder Ultimate Strength of Large Container Ships

2016 ◽  
Author(s):  
Toshiyuki Matsumoto ◽  
Toshiyuki Shigemi ◽  
Mitsuhiko Kidogawa ◽  
Kinya Ishibashi ◽  
Kei Sugimoto
Keyword(s):  
Ultimate Strength ◽  
Bending Moment ◽  
Lateral Loads ◽  
Hull Girder ◽  
Local Strength ◽  
The Difference ◽  
Collapse Behavior ◽  
Large Container ◽  
Vertical Bending Moment

It is known that the hull girder ultimate strength with consideration of lateral loads such as bottom sea pressures and/or cargo loads generally decreases than that without consideration of the lateral loads (i.e. the effect of lateral loads). In this study a series of elasto-plastic analyses of three cargo holds models, which can reproduce the collapse behavior of the hold structures subjected to both vertical bending moment and lateral loads such as bottom sea pressures, container cargo loads etc., were carried out on a number of container ships with various sizes, and the hull girder ultimate strength obtained through the analyses were comparatively examined focusing on the effect of the lateral loads. As results of the examination, it has been concluded that local strength of the double bottom structure against the lateral loads is closely related to the hull girder ultimate strength in the case of container ships, the effect of the lateral loads on the hull girder ultimate strength varies among container ships due to the difference of construction of the double bottom structure and it is important to assess the hull girder ultimate strength explicitly taking into consideration the effect of the lateral loads for large container ships such as Post-Panamax sizes.

Calculation of Vertical Bending Moment Acting on an Ultra Large Containership in Large Amplitude Waves

2015 ◽  
Author(s):  
Suresh Rajendran ◽  
Nuno Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Large Amplitude ◽  
Bending Moment ◽  
Regular Waves ◽  
Structural Dynamic ◽  
Strip Theory ◽  
Structural Dynamic Characteristics ◽  
Wetted Surface Area ◽  
The Time Domain ◽  
Hydroelastic Response ◽  
Vertical Bending Moment

The time domain method is further extended here in order to calculate the hydroelastic response of an ultra large containership in regular waves. Based on strip theory, the hydrodynamic and the hydrostatic forces are calculated for the instantaneous wetted surface area. Slamming forces are calculated using a Von Karman approach in which the water pile up during slamming is neglected. Timoshenko beam which takes into account the shear deformation and rotary inertia is used to model the structural dynamic characteristics of the hull. The beam is discretized using the finite element method and the ship vibration is solved using the modal analysis. The method is used to calculate the vertical bending moment acting on an ultra large containership in large amplitude regular waves. The results are compared with the experimental results measured in wave tank.

Sign in / Sign up

Export Citation Format

Share Document