Maneuvering Behavior of Ships in Irregular Waves

2013 ◽  
Author(s):  
Renato Skejic ◽  
Odd M. Faltinsen
Keyword(s):  
Deep Water ◽  
Cross Flow ◽  
Irregular Waves ◽  
Scale Model ◽  
Wave Loads ◽  
Ship Maneuvering ◽  
Slender Body Theory ◽  
Statistical Point ◽  
Irregular Wave ◽  
Mmg Model

Ship maneuvering in waves is analyzed by using a unified seakeeping and maneuvering two-time scale model in irregular sea that has been applied by Skejic and Faltinsen [1] for regular waves. The irregular wave effects are accounted for by Newman’s [2] approximation of the slow-drift 2nd order wave loads valid for deep water (Faltinsen [3], Pinkster [29]). The modular type maneuvering model (MMG model) based on Söding’s [4] nonlinear slender-body theory is used for the maneuvering analysis. Forces and moments due to rudder, propeller, and viscous cross-flow are accounted for as presented by Skejic and Faltinsen [1] and Yasukawa [5, 6]. In particular, the behavior of the propulsive coefficients (the thrust deduction and wake fraction) in waves (Faltinsen et al. [7], Faltinsen and Minsaas [8]) are discussed from the perspective of ship maneuvering characteristics in both regular and irregular wave environments. The unified model of seakeeping and maneuvering for deep-water irregular waves is validated for the ‘S7-175’ (‘SR 108’) container ship in calm water and regular deep-water wave scenarios by comparison with experimental results by Yasukawa [5, 6]. The maneuvering model is applied to a ‘MARINER’ ship performing turning maneuver in irregular waves. The obtained results of the ships main maneuvering parameters are discussed from a statistical point of view.

scholarly journals NON-BREAKING AND BREAKING WAVE LOADS ON A COOLING WATER OUTFALL

1978 ◽  
Vol 1 (16) ◽  
pp. 148
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Water Level ◽  
Cooling Water ◽  
High Water ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Scale Model ◽  
Breaking Wave ◽  
Wave Loads ◽  
Eastern Canada ◽  
Spilling Breakers

Cooling water from a power generating station in Eastern Canada is pumped to an outfall and distributed into the ocean through discharge ports in the sidewalls of a diffuser cap. The cap is essentially a shell-type structure consisting of a submerged circular cylinder 26.5 ft in diameter and 14 ft high. It is located in 25 ft of water at low water level and 54 ft at high water level. Horizontal forces, vertical forces and overturning moments exerted by waves on a 1:36 scale model of the diffuser cap were measured with and without cooling water discharging from the outfall. Tests were run with regular and irregular waves producing both non-breaking and breaking wave loads on the diffuser cap. The overturning moments measured on the diffuser cap were up to 150 percent greater than those on a solid submerged cylinder sealed to the seabed. Unlike sealed cylinders, all of the wave loads measured on the relatively open structure reached maximum values at approximately the same time. The largest wave loads were measured on the diffuser structure when it was subjected to spilling breakers at low water level. For a given wave height, the spilling breakers caused wave loads up to 100 percent greater than those due to non-breaking waves.

Hydrodynamic Performance of a Novel Free Surface Pitching Breakwater

2014 ◽  
Author(s):  
Vengatesan Venugopal ◽  
Stefan Zlatev
Keyword(s):  
Body Shape ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Scale Model ◽  
Reflected Waves ◽  
Irregular Wave ◽  
Wave Flume ◽  
Floating Breakwater ◽  
Wave Heights ◽  
Transmission Ct

A new concept floating breakwater was developed and tested to evaluate its hydrodynamic performance in this paper. This innovative floating breakwater has a rocking body shape which could also be used as a wave power device. A scale model was tested in a wave flume under regular and irregular wave conditions for various combinations of wave frequencies and wave heights. The breakwater has been tested for three immersion depths of 0.05 m, 0.09 m and 0.13 m from still water level. The measured transmitted and reflected waves were used to evaluate the coefficients of transmission (CT), reflection (CR) and dissipation (CL). The results illustrated that the breakwater model performed at its best when submerged at 0.13m, as this immersion depth produced lower coefficients of transmission (CT), lower reflection coefficients (CR) and higher energy dissipation (CL) coefficients. The comparison between regular and irregular waves produced similar ranges of transmission, reflection and energy coefficients.

scholarly journals Free Surface Reconstruction for Phase Accurate Irregular Wave Generation

2018 ◽  
Vol 6 (3) ◽  
pp. 105 ◽  
Author(s):  
Ankit Aggarwal ◽  
Csaba Pákozdi ◽  
Hans Bihs ◽  
Dag Myrhaug ◽  
Mayilvahanan Alagan Chella
Keyword(s):  
Free Surface ◽  
Surface Reconstruction ◽  
Deep Water ◽  
Time Domain ◽  
Present Approach ◽  
Surface Elevation ◽  
Irregular Waves ◽  
Free Surface Elevation ◽  
Irregular Wave ◽  
The Time Domain

The experimental wave paddle signal is unknown to the numerical modellers in many cases. This makes it quite challenging to numerically reproduce the time history of free surface elevation for irregular waves. In the present work, a numerical investigation is performed using a computational fluid dynamics (CFD) based model to validate and investigate a non-iterative free surface reconstruction technique for irregular waves. In the current approach, the free surface is reconstructed by spectrally composing the irregular wave train as a summation of the harmonic components coupled with the Dirichlet inlet boundary condition. The verification is performed by comparing the numerically reconstructed free surface elevation with theoretical input waves. The applicability of the present approach to generate irregular waves by reconstructing the free surface is investigated for different coastal and marine engineering problems. A numerical analysis is performed to validate the free surface reconstruction approach to generate breaking irregular waves over a submerged bar. The wave amplitudes, wave frequencies and wave phases are modelled with good accuracy in the time-domain during the higher-order energy transfers and complex processes like wave shoaling, wave breaking and wave decomposition. The present approach to generate irregular waves is also employed to model steep irregular waves in deep water. The free surface reconstruction method is able to simulate the irregular free surface profiles in deep water with low root mean square errors and high correlation coefficients. Furthermore, the irregular wave forces on a monopile are investigated in the time-domain. The amplitudes and phases of the force signal under irregular waves generated by using the current technique are modelled accurately in the time-domain. The proposed approach to numerically reproduce the free surface elevation in the time-domain provides promising and accurate results for all the benchmark cases.

scholarly journals Emergence of Solitons from Irregular Waves in Deep Water

2021 ◽  
Vol 9 (12) ◽  
pp. 1369
Author(s):  
Weida Xia ◽  
Yuxiang Ma ◽  
Guohai Dong ◽  
Jie Zhang ◽  
Xiaozhou Ma
Keyword(s):  
Deep Water ◽  
Rogue Wave ◽  
Wave Train ◽  
Irregular Waves ◽  
Peak Wavelength ◽  
Long Distance ◽  
Irregular Wave ◽  
Resonant Interactions ◽  
Dispersion Effects ◽  
Wave Trains

Numerical simulations were performed to study the long-distance evolution of irregular waves in deep water. It was observed that some solitons, which are the theoretical solutions of the nonlinear Schrödinger equation, emerged spontaneously as irregular wave trains propagated in deep water. The solitons propagated approximately at a speed of the linear group velocity. All the solitons had a relatively large amplitude and one detected soliton’s height was two times larger than the significant wave height of the wave train, therefore satisfying the rogue wave definition. The numerical results showed that solitons can persist for a long distance, reaching about 65 times the peak wavelength. By analyzing the spatial variations of these solitons in both time and spectral domains, it is found that the third-and higher-order resonant interactions and dispersion effects played significant roles in the formation of solitons.

scholarly journals Numerical Simulation of Fully Nonlinear Interaction Between Regular and Irregular Waves and a 2D Floating Body

2019 ◽  
Author(s):  
Haoran Li ◽  
Erin E. Bachynski
Keyword(s):  
Numerical Results ◽  
The Body ◽  
Body Motion ◽  
Irregular Waves ◽  
Floating Body ◽  
Computational Time ◽  
Wave Loads ◽  
Nonlinear Loads ◽  
Fully Nonlinear ◽  
Irregular Wave

Abstract A fully nonlinear Navier-Stokes/VOF numerical wave tank, developed within the open-source CFD toolbox OpenFOAM, is used to investigate the response of a moored 2D floating body to nonlinear wave loads. The waveDyMFoam solver, developed by extending the interDyMFoam solver of the OpenFOAM library with the waves2Foam package, is applied. Furthermore, a simple linear spring is implemented to constrain the body motion. An efficient domain decomposition strategy is applied to reduce the computational time of irregular wave cases. The numerical results are compared against the results from potential flow theory. Numerical results highlight the coupling between surge and pitch motion and the presence of nonlinear loads and responses. Some minor numerical disturbance occurs when the maximum body motion response is achieved.

Numerical Evaluation of Ship Maneuvering Performance in Waves

2018 ◽  
Author(s):  
Min-Guk Seo ◽  
Bo Woo Nam ◽  
Yeon-gyu Kim
Keyword(s):  
Irregular Waves ◽  
Time Signal ◽  
Regular Waves ◽  
Ship Maneuvering ◽  
Wave Drift ◽  
Mmg Model ◽  
Free Running ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

This paper considers a numerical computation of ship maneuvering performance in waves. For this purpose, modular-type maneuvering model (MMG model) is adopted and wave drift forces and moments are included in maneuvering equation of motion. Wave drift forces ware calculated using a seakeeping program based on higher-order Rankine panel method. When calculating the wave drift force acting on a ship, the forward speed, wave heading, wave period and drift angle of the ship are considered as key parameters. It means that ship’s lateral speed is also included to calculate wave drift force. Numerical simulations are carried out in regular waves using S175 containership and computation results are validated by comparing them with results of free-running model test. Using the developed program, numerical simulation in irregular waves are, also, conducted and discussion is made on the sensitivities of time signal of wave elevation on turning performance.

scholarly journals A Heuristic Approach for Inter-Facility Comparison of Results from Round Robin Testing of a Floating Wind Turbine in Irregular Waves

2021 ◽  
Vol 9 (9) ◽  
pp. 1030
Author(s):  
Sebastien Gueydon ◽  
Frances Judge ◽  
Eoin Lyden ◽  
Michael O’Shea ◽  
Florent Thiebaut ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Round Robin ◽  
Irregular Waves ◽  
Scale Model ◽  
Test Results ◽  
Floating Platform ◽  
Global Trends ◽  
Irregular Wave ◽  
Floating Wind Turbine ◽  
Decay Tests

This paper introduces metrics developed for analysing irregular wave test results from the round robin testing campaign carried out on a floating wind turbine as part of the EU H2020 MaRINET2 project. A 1/60th scale model of a 10 MW floating platform was tested in wave basins in four different locations around Europe. The tests carried out in each facility included decay tests, tests in regular and irregular waves with and without wind thrust, and tests to characterise the mooring system as well as the model itself. While response amplitude operations (RAOs) are a useful tool for assessing device performance in irregular waves, they are not easy to interpret when performing an inter-facility comparison where there are many variables. Metrics that use a single value per test condition rather than an RAO curve are a means of efficiently comparing tests from different basins in a more heuristic manner. In this research, the focus is on using metrics to assess how the platform responds with varying wave height and thrust across different facilities. It is found that the metrics implemented are very useful for extracting global trends across different basins and test conditions.

High frequency resonant response of a monopile in irregular deep water waves

2018 ◽  
Vol 853 ◽  
pp. 564-586 ◽  
Author(s):  
Bjørn Hervold Riise ◽  
John Grue ◽  
Atle Jensen ◽  
Thomas B. Johannessen
Keyword(s):  
Resonance Frequency ◽  
Deep Water ◽  
Water Waves ◽  
Irregular Waves ◽  
Breaking Wave ◽  
Wave Load ◽  
Irregular Wave ◽  
The Third ◽  
Extreme Response ◽  
Wave Slope

Experiments with a weakly damped monopile, either fixed or free to oscillate, exposed to irregular waves in deep water, obtain the wave-exciting moment and motion response. The nonlinearity and peak wavenumber cover the ranges: $\unicode[STIX]{x1D716}_{P}\sim 0.10{-}0.14$ and $k_{P}r\sim 0.09{-}0.14$ where $\unicode[STIX]{x1D716}_{P}=0.5H_{S}k_{P}$ is an estimate of the spectral wave slope, $H_{S}$ the significant wave height, $k_{P}$ the peak wavenumber and $r$ the cylinder radius. The response and its statistics, expressed in terms of the exceedance probability, are discussed as a function of the resonance frequency, $\unicode[STIX]{x1D714}_{0}$ in the range $\unicode[STIX]{x1D714}_{0}\sim 3{-}5$ times the spectral peak frequency, $\unicode[STIX]{x1D714}_{P}$. For small wave slope, long waves and $\unicode[STIX]{x1D714}_{0}/\unicode[STIX]{x1D714}_{P}=3$, the nonlinear response deviates only very little from its linear counterpart. However, the nonlinearity becomes important for increasing wave slope, wavenumber and resonance frequency ratio. The extreme response events are found in a region where the Keulegan–Carpenter number exceeds $KC>5$, indicating the importance of possible flow separation effects. A similar region is also covered by a Froude number exceeding $Fr>0.4$, pointing to surface gravity wave effects at the scale of the cylinder diameter. Regarding contributions to the higher harmonic forces, different wave load mechanisms are identified, including: (i) wave-exciting inertia forces, a function of the fluid acceleration; (ii) wave slamming due to both non-breaking and breaking wave events; (iii) a secondary load cycle; and (iv) possible drag forces, a function of the fluid velocity. Also, history effects due to the inertia of the moving pile, contribute to the large response events. The ensemble means of the third, fourth and fifth harmonic wave-exciting force components extracted from the irregular wave results are compared to the third harmonic FNV (Faltinsen, Newman and Vinje) theory as well as other available experiments and calculations. The present irregular wave measurements generalize results obtained in deep water regular waves.

Large-Scale Experiments of Wave-Overtopping Loads on Walls: Layer Thicknesses and Velocities

2018 ◽  
Author(s):  
Lorenzo Cappietti ◽  
Irene Simonetti ◽  
Andrea Esposito ◽  
Maximilian Streicher ◽  
Andreas Kortenhaus ◽  
...  
Keyword(s):  
Large Scale ◽  
Scale Validation ◽  
Irregular Waves ◽  
Scale Model ◽  
Small Scale ◽  
Wave Loads ◽  
Wave Overtopping ◽  
Large Scale Model ◽  
Vertical Walls ◽  
Set Up

Wave-Overtopping loads on vertical walls, such as those located on top of a dike, have been investigated in several small-scale experiments in the past. A large-scale validation for a mild foreshore situation is still missing. Hence the WALOWA (WAve LOads on WAlls) experimental campaign was carried out to address this topic. This paper, first presents a description of the large-scale model, the measurement set-up and the experimental methodologies, then it focuses on the layer thicknesses and velocities of the flows created on the promenade by the wave overtopping. A set of resistive wave gauges, ultrasonic distance sensors and velocimeters have been used to conduct these measurements. Preliminary data analysis and results, related to a 1000 irregular waves long test, are discussed. The momentum flux of these flows is studied and its implications, for the wave-overtopping loads acting on the vertical walls, are highlighted.

Evaluation of Response Amplitude Operator of Ship Roll Motions Based on the Experiments in White Noise Waves

2017 ◽  
Author(s):  
Sebastian Bielicki ◽  
Antoni Bednarek ◽  
Marek Kraskowski
Keyword(s):  
White Noise ◽  
Response Amplitude ◽  
Irregular Waves ◽  
Scale Model ◽  
Roll Motion ◽  
Viscous Damping ◽  
Regular Waves ◽  
Irregular Wave ◽  
Decay Test ◽  
Ship Roll

Evaluation of the response amplitude operator (RAO) function for ship wave frequency motions by means of scale model tests in regular waves is a standard procedure conducted by hydrodynamic model testing institutions. The resulting RAO function allows for evaluating sufficiently reliable seakeeping predictions for low to moderate sea states. However, for standard hull forms, correct prediction of roll motion in irregular wave (and also in regular waves different than these used in the experiment) on the basis of RAO function presents a substantial challenge due to considerable contribution of viscous damping to roll response. In other words, the RAO values depend strongly on the amplitude of the waves used in the experiment, so the final prediction requires careful application of relevant correction of RAO, dependent on the actual significant wave height, for which the prediction is computed. Thus, in order to collect complete data for ship roll prediction, the roll decay test is usually also required. Additional drawback of evaluating the seakeeping prediction on the basis of RAO is the fact that the experiment in regular waves is quite time-consuming, which refers to the experiment itself as well as to the processing. The following paper presents a proposal of the alternative method for experimental evaluation of response amplitude operator of roll motion in beam waves, consisting in exposing the ship model to irregular wave characterized by white noise spectrum, i.e. the spectrum of uniform energy density. In theory, RAO function is equivalent to the square root of the spectrum of the response to white noise wave. The results of experiments in white noise waves were verified on the basis of the results of comprehensive experiments conducted in usual way. Additionally, the effect of non-linearity of viscous damping was widely studied by comparing the calibrated RAO-based predictions with actual response to irregular waves of different heights. As a result, a method for including the non-linear effects in prediction based on white noise was proposed. It was proved that the proposed method is capable of providing equally valuable information in significantly shorter time.

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