scholarly journals Prediction of Extreme Ship Motions in Irregular Waves

PAMM ◽  
2005 ◽  
Vol 5 (1) ◽  
pp. 723-724 ◽  
Author(s):  
Edwin Kreuzer ◽  
Wolfgang Sichermann
Keyword(s):  
Irregular Waves ◽  
Ship Motions

Non Linear Effect on Wave-Induced Loads for Hull Structural Design: Bulk Carrier, Container Carrier, Vehicles Carrier

2020 ◽  
Author(s):  
Kei Sugimoto ◽  
Yusuke Fukumoto ◽  
Junya Matsuwaki ◽  
Tatsuya Akamatsu ◽  
Shinsaku Ashida ◽  
...  
Keyword(s):  
Hydrodynamic Pressure ◽  
Irregular Waves ◽  
Structural Safety ◽  
Sensor Technology ◽  
Ship Motions ◽  
Bulk Carrier ◽  
Structural Rules ◽  
Linear Effect ◽  
Non Linear ◽  
Linear Effects

Abstract The structural rules of classification societies typically specify various loads corresponding to the most severe sea states which are expected to be encountered by a ship throughout her service life in order to ensure ship structural safety, and these rules also usually define a variety of simplified formulae to aid in the calculation of such loads. In most cases, such formulae have been developed using linear seakeeping codes and linear statistical predictions; such methods, however, do not typically take into account some complex phenomena due to theoretical and methodological limitations. For this reason, the use of values obtained through linear theory alone is often not sufficient to properly evaluate structural strength, and it is, therefore, necessary to consider other things such as non-linear effects and operational effects. Although the structural rules of classification societies normally take into account such effects, most of them generally treat such things simply as either a constant coefficient or as an implicit condition because of the difficulty of expressing such effects mathematically (i.e. as specific formulae) as well as a general lack of prior research related to such effects. In this paper, the authors present the results of tank tests and numerical calculations carried out in regular and irregular waves using a bulk carrier, a container carrier and a vehicles carrier, and discuss possible ways of improving the non-linear coefficients specified in the IACS Common Structural Rules (CSR) [1]. Load states, including their non-linear effects, were investigated by examining the behavior of ship motions and hydrodynamic pressure. In order to investigate the behavior of pressure in detail, the pressure acting upon the hull surfaces of the target ships was measured at over 300 locations using a FBG sensor, the latest in optical fiber sensor technology [2].

Numerical Simulation of Ship Motions in Regular and Irregular Waves

2019 ◽  
Vol 53 (1) ◽  
pp. 97-106
Author(s):  
Bao-Ji Zhang ◽  
Jie Liu ◽  
Ning Xu ◽  
Lei Niu ◽  
Wen-Xuan She
Keyword(s):  
Numerical Simulation ◽  
Wave Length ◽  
Simulation Method ◽  
Irregular Waves ◽  
Navier Stokes ◽  
Ship Motions ◽  
Vof Model ◽  
Split Operator ◽  
Strip Theory ◽  
Cfd Method

AbstractA numerical simulation method is presented in this study to predict ship resistance and motion responses in regular and irregular waves. The unsteady RANS (Reynolds Average Navier-Stokes) method is selected as the governing equation, and a volume of fluid (VoF) model is used to capture the free surface, combining the k-ε equations. A finite volume method (FVM) is utilized to discretize both the RANS equations and VoF transport equation. The pressure implicit split operator (PISO) method is set as the velocity-pressure coupling equation. The overset mesh technique is utilized to simulate ship motions in waves. A DTMB5415 ship is selected as a case study to predict its pitch and heave responses in regular and irregular waves at different wave length and wave steepness. The ship is free to move in the pitch and heave directions. The CFD (Computational Fluid Dynamics) results are found to be in good agreement with the strip theory and experimental data. It can be found that the CFD method presented in this study can provide a theoretical basis and technical support for green design and manufacture of ships.

Evaluation method of motion seasickness by ship motions during underway in irregular waves

2015 ◽  
Vol 51 (1) ◽  
pp. 71-78 ◽  
Author(s):  
Chan-Moon CHOI ◽  
◽  
Chang-Heon LEE ◽  
Byung-Yeob KIM ◽  
Jang-Young AHN ◽  
...  
Keyword(s):  
Evaluation Method ◽  
Irregular Waves ◽  
Ship Motions

Aframax in Numerical Wave Tank: From Classic Decay Test to the Ship Moored in Irregular Waves

2016 ◽  
Author(s):  
Daniel Barcarolo ◽  
Olivia Thilleul ◽  
David le Touzé ◽  
Erwan Jacquin ◽  
Igor de Vries ◽  
...  
Keyword(s):  
Numerical Model ◽  
Stokes Equations ◽  
Back Propagation ◽  
Irregular Waves ◽  
Navier Stokes ◽  
Ship Motions ◽  
Diffraction Radiation ◽  
Decay Test ◽  
Decay Tests ◽  
Set Up

The prediction of ship motions in extreme seastates is very complex as it involves strong nonlinearities. It deals with high motions of the ship and implies strong mooring system loads. These seastates are usually modeled in tank tests but an alternative in the near future could be CFD computations. In this article, all required steps to setup and verify the hydrodynamic and numerical model are performed. The setup of the hydrodynamic and numerical model enable us to show that CFD computations of motion RAOS and pitch decay tests provide results in agreement with diffraction-radiation results. Wave only simulations enable us to verify that irregular waves are accurately modelled in the CFD domain. Since the wavemaker motion used in tank tests to generate irregular waves is not available, a process of linear back propagation is set up from the wave elevation on a wave probe in tank tests. High Order Spectral (HOS) simulations are performed to reproduce the seastate measured in tank tests. Finally, a test was performed to model the ship motions in irregular extreme waves with ICARE solver coupled to the computed HOS wave field through Spectral Wave Explicit Navier Stokes Equations (SWENSE).

Nonlinear Roll Damping of Ship Motions in Waves

2005 ◽  
Vol 127 (3) ◽  
pp. 205-211 ◽  
Author(s):  
Xiaorong Wu ◽  
Longbin Tao ◽  
Yuanlin Li
Keyword(s):  
Experimental Investigation ◽  
Ocean Waves ◽  
Irregular Waves ◽  
Ship Motions ◽  
Roll Damping ◽  
Segment Number ◽  
Data Process ◽  
Profound Influence ◽  
Random Decrement ◽  
Random Decrement Method

Nonlinear roll damping has a profound influence on ship motions and stability in ocean waves. In this study, an experimental investigation is conducted on the nonlinear roll damping of a ship in regular and irregular waves. The random decrement method, previously used in linear roll damping prediction, is extended to nonlinear roll damping estimation in the data process. The accuracy of the nonlinear roll damping obtained by using the random decrement method is found to be dependent on the values of the threshold and segment number.

Numerical Research on Ship Motions in Oblique Irregular Waves

2013 ◽  
Vol 712-715 ◽  
pp. 1531-1534
Author(s):  
Ming Wu ◽  
Ai Guo Shi ◽  
Zuo Chao Wang ◽  
Xiao Wang ◽  
Rong Rong Ying
Keyword(s):  
Transfer Functions ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Irregular Waves ◽  
Ship Motions ◽  
Time Step ◽  
Oblique Waves ◽  
Surface Ship ◽  
Calculation Results ◽  
Numerical Research

A 3D viscous numerical wave tank (NWT) was established based on computational fluid dynamics simulation method, and oblique irregular waves were generated by defining inflow boundary conditions. The motions of free surface ship in oblique waves were predicted by solving the Reynolds Averaged NavierStokes (RANS) equations describing the flow around ship. The kinematics equations of rigid body were solved according to the calculation results (forces and moments) in each time step. The heave, roll and pitch transfer functions for container ship model S175 in oblique waves were obtained. The comparisons between simulation results and linear strip theoretical results were carried out, showing good agreement, which demonstrate the present research can provide an effective way to predict seakeeping characteristics.

Seakeeping

1991 ◽  
Vol 334 (1634) ◽  
pp. 253-264
Keyword(s):  
Transfer Functions ◽  
Early Stage ◽  
Vertical Plane ◽  
Irregular Waves ◽  
Ship Motions ◽  
More Care ◽  
Permissible Levels ◽  
Calm Weather ◽  
Time Required ◽  
The Way

It is well known that ship performance is degraded in rough weather. In moderately severe conditions every task on board the ship will take longer than it does in calm weather. The passengers and crew may be seasick and they will have to take more care when moving around the ship to avoid injury. The physical performance of mechanical and electrical systems may also be reduced if the ship motions are severe. Cargo may be damaged and this may also be considered as a reduction in performance. In extreme conditions, the ship may capsize or founder and this is, of course, the ultimate loss of performance. The aim of research in seakeeping is, or should be, to develop techniques of predicting the degradation of performance a ship will experience in rough weather. If this can be achieved it will enable the ship designer to eliminate unsatisfactory and unsafe ships at an early stage in the design process. The paper begins by summarizing the standard techniques for predicting the motions a ship will experience in rough weather. These are based on well-known strip theories coupled with superposition techniques for inferring the statistics of the motions in irregular waves from the regular wave transfer functions. These techniques are quite well validated for conventional monohull ship motions in the vertical plane but predictions of motions in the lateral plane are rather less reliable and further work is needed in this area. Accurate predictions of the irregular motions in realistic sea states are only one step in achieving the ultimate goal of predicting the rough-weather performance of new designs of ships. We also need to estimate the maximum permissible levels of the motions (usually known as seakeeping criteria). There are, in principle, no universally applicable criteria. They depend on the activities within the ship while it is engaged in a given mission and also on the type of equipment used. We therefore need to quantify the way in which the performance of the various sub systems or tasks which make up the ship mission degrade in rough weather. Ideally the first step should be to examine each task (or at least a representative selection of the important tasks) and to study the way in which the performance degrades. This will allow the motions (or other rough-weather phenomena) which are important for that particular task to be identified. It is then necessary to determine the maximum permissible levels of these motions by simulation, questionnaires, trials or even guesswork. Finally there is a need to develop universally acceptable measures of performance. Ideally these might include elements of the time required to complete a task (in relation to the time required in calm weather) as well as the quality of the result.

The Simulation of Ship Motions Using a B-Spline–Based Panel Method in Time Domain

2007 ◽  
Vol 51 (03) ◽  
pp. 267-284
Author(s):  
Ranadev Datta ◽  
Debabrata Sen
Keyword(s):  
Time Domain ◽  
Three Dimensional ◽  
Basis Functions ◽  
The Body ◽  
Irregular Waves ◽  
Ship Motions ◽  
B Spline ◽  
Head Waves ◽  
Wigley Hull ◽  
Spline Basis

In this paper, a B-spline-based higher-order method is developed for simulating three-dimensional ship motions with forward speed. The problem is formulated in time domain using a transient free surface Green function. The body geometry is defined by open uniform or nonuniform B-spline basis functions depending on the hull type, whereas the unknown field variables are described by open uniform B-spline basis functions. The collocation method is applied to discretize the integral equation and then solved for the unknown potentials and source strengths. Motion computations in head waves are carried out for three types of ship hulls: a mathematically defined Wigley hull, a typical containership (S175 hull), and a Series 60 hull. Results are obtained for regular and irregular waves and compared with available experimental and computational results. It is found that the results from the present method are in very good agreement with the published results, and in particular with experimental data. Long-duration simulations have also been carried out with an ordinary desktop PC (PIV with 512 MB RAM) to demonstrate the ability of the method to simulate motions over long periods without any visible deterioration using only modest computational resources.

Large Two-Stroke Marine Diesel Engine Operation with a High-Pressure SCR System in Heavy Weather Conditions

2020 ◽  
pp. 1-15 ◽  
Author(s):  
Michael I. Foteinos ◽  
George I. Christofilis ◽  
Nikolaos P. Kyrtatos
Keyword(s):  
High Pressure ◽  
Weather Conditions ◽  
Irregular Waves ◽  
Ship Motions ◽  
Exhaust Gas ◽  
Time Varying ◽  
Gas Temperature ◽  
Marine Diesel ◽  
Exhaust Gas Temperature ◽  
Scr System

The transient performance of a direct-drive large two-stroke marine diesel engine, installed in a vessel operating in a seaway with heavy weather, is investigated via simulation. The main engine of the ship is equipped with a selective catalytic reduction (SCR) after treatment system for compliance with the latest International Maritime Organization (IMO) rules for NOx reduction, IMO Tier III. Because of limitations of exhaust gas temperature at the inlet of SCR systems and the low temperature exhaust gases produced by marine diesel engines, in marine applications, the SCR system is installed on the high-pressure side of the turbine. When a ship sails in heavy weather, it experiences a resistance increase, wave-induced motions, and a time-varying flow field in the propeller, induced by ship motions. This results in a fluctuation of the propeller torque demand and, thus, a fluctuation in engine power and exhaust gas temperature, which can affect engine and SCR performance. To investigate this phenomenon and take into account the engine–propeller interaction, the entire propulsion plant was modeled, namely, the slow-speed diesel propulsion engine, the high-pressure SCR system, the directly driven propeller, and the ship's hull. To simulate the transient propeller torque demand, a propeller model was used, and torque variations due to ship motions were taken into account. Ship motions in waves and wave-added resistance were calculated for regular and irregular waves using a 3D panel code. The coupled model was validated against available measured data from a shipboard propulsion system in good weather conditions. The model was then used to simulate the behavior of a Tier III marine propulsion plant during acceleration from low to medium load, in the presence of regular and irregular waves. The effect of the time-varying propeller demand on the engine and the SCR system was investigated. 1. Introduction The effect of waves on a marine propulsion system is a complex phenomenon involving interactions between different subsystems of the propulsion plant, i.e., the prime mover, the propeller, and the ship's hull. Ships sailing in heavy weather conditions experience a resistance increase, wave-induced motions, and a time-varying flow field in the propeller. This leads to a fluctuation of the propeller torque demand which results in a fluctuation in engine-produced power and exhaust gas temperature.

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