scholarly journals Influence of the aspect ratio of energy-saving wing elements fitted on the ship bottom upon spectral densities of longitudinal motions in irregular waves

2020 ◽  
pp. 45-51
Author(s):  
З.М. Хтет ◽  
К.В. Рождественский
Keyword(s):  
Aspect Ratio ◽  
Energy Saving ◽  
Calculated Data ◽  
Irregular Waves ◽  
Ship Motions ◽  
Wave Spectra ◽  
Regular Waves ◽  
Spectral Densities ◽  
Strip Theory ◽  
Oscillating Foil

В статье приводятся оценки спектральных плотностей качки судна с энергосберегающими крыльевыми элементами на встречном нерегулярном волнении, а также результаты сравнения расчета и эксперимента для продольной качки судна на регулярном волнении. Метод расчета основан на линейной теории поперечных сечений в частотной области. При этом сначала рассматривается продольная качка на встречном регулярном волнении с учетом демпфирующего и инерционного влияния крыльев посредством привлечения теории Теодорсена колеблющегося крыла. Определение спектральной плотности продольной качки на нерегулярном волнении проводится на основании формулы А.Я. Хинчина. Для расчета спектра волнения используется спектр JONSWAP по рекомендации DNV GL(2018). В ходе расчетов демонстрируется влияние на спектральные плотности удлинения и площади энергосберегающих крыльев, а также на спектральные плотности качки при совместном использовании носового и кормового крыльев по сравнению со случаем использования только одного из этих крыльев. Полученные расчетные данные дают представление о механизме снижения спектральных плотностей при использовании крыльев. The article presents some estimates of spectral densities of longitudinal motions for a ship with energy-saving wing devices in headwind irregular waves, and also comparisons of calculated and experimental data for longitudinal ship motions in headwind regular waves. The calculation method is based on a linear strip theory in frequency domain. Considered first are longitudinal motions of a ship in headwind regular waves with account of inertial and damping influence of the wings through use of Theodorsen oscillating foil theory. Spectral densities of longitudinal motions in irregular waves are determined with use of A.Ya. Khinchin formula and JONSWAP wave spectra as recommended by DNV GL (2018). Demonstrated in the course of calculations is the influence of the wings aspect ratio and area as well as their position with respect to the ship hull (bow wing, stern wing, bow & stern wings). Calculated data gives an idea of the mechanism of spectral densities reduction for motions of a ship with wing elements.

scholarly journals Исследования особенностей снижения продольной качки и дополнительного сопротивления судна с крыльевыми устройствами

2020 ◽  
Author(s):  
Z.M. Htet
Keyword(s):  
Energy Saving ◽  
Orbital Motion ◽  
Calculated Data ◽  
Ship Motions ◽  
Added Resistance ◽  
Regular Waves ◽  
Kinematic Parameters ◽  
Coupled Equations ◽  
Added Resistance In Waves ◽  
Oscillating Foil

В данной статье на основе предложенного расчета качки судна с энергосберегающими крыльевыми устройствами производится оценка мореходности и ходкости такого судна и возможности целенаправленного уменьшения амплитуд качки и снижения дополнительного сопротивления на волнении. Продольная качка судна заданного типа, обводов и размерений при наличии крыльевых элементов на заданном регулярном волнении рассчитывается с привлечением совместных уравнений вертикально-килевой качки с учетом демпфирования и инерции крыльевых устройств. При этом используется теория Теодорсена колеблющегося профиля и разложение нестационарных коэффициентов подъемной силы и момента по кинематическим параметрам при комбинировании вертикальных и угловых колебаний, и, в общем случае, в условиях воздействия орбитального движения жидкости. Для оценки дополнительного сопротивления используется теория Герритсмы и Бекельмана. В ходе расчетов демонстрируется влияние на дополнительное сопротивление удлинения и площади энергосберегающих крыльев, а также возможности снижения дополнительного сопротивления при совместном использовании носового и кормового крыльев по сравнению со случаем использования только одного (носового или кормового) крыла. Полученные расчетные данные позволяют получить представление о механизме влияния энергосберегающих крыльев на умерение амплитуд качки и снижение дополнительного сопротивления на волнении.In this article on the basis of the method for calculation of longitudinal motions of a ship with energy-saving wing devices proposed there is made an estimation of seaworthiness and seagoing capacity of such a ship and also of a possibility of directed decrease of ship motions amplitudes and added resistance in waves. The longitudinal motions of a ship of a given type, configuration and dimensions, in presence of wing elements, and in given regular waves is calculated with use of coupled equations of heave and pitch motions with account of damping and inertia of wing devices. Used therewith is Theodorsen theory of oscillating foil and expansion of lift and moment coefficients with respect to kinematic parameters for combined heave-and-pitch oscillations and, in general case, subject to action of orbital motion of fluid particles. To estimate added resistance the Beuklman-Gerritsma theory is used. Demonstrated in the course of calculations is the influence of aspect ratio and area of energy-saving wing upon the added resistance as well as upon its decrease when combining use of both bow and stern wings as compared to the case of using just one (bow or stern) wing. Obtained calculated data allow to understand the mechanism of the influence of energy-saving wings upon decrease of the amplitude of ship motions and the added resistance in waves.

scholarly journals On the issue of reduction of relative motion of the bow for a ship with energy-saving wing elements in headwind waves

2020 ◽  
pp. 52-58
Author(s):  
З.М. Хтет ◽  
К.В. Рождественский
Keyword(s):  
Experimental Data ◽  
Aspect Ratio ◽  
Energy Saving ◽  
Relative Motion ◽  
Vertical Displacement ◽  
Regular Waves ◽  
Method Of Calculation ◽  
Strip Theory ◽  
Vertical Displacements ◽  
Oscillating Foil

В статье рассматривается относительное перемещение носовой оконечности судна с энергосберегающими крыльевыми элементами на встречном волнении, а также результаты сравнения соответствующих расчетных и экспериментальных данных. Метод расчета основан на линейной теории поперечных сечений в частотной области. Сначала производится расчет продольной (вертикальной и килевой) качки судна встречном волнении, а затем расчетные данные используются для расчета относительных перемещений точек корпуса судна. Далее, для найденных численным методом смешанных колебаний носового и кормового крыльев, с привлечением теории Теодорсена колеблющегося профиля. В ходе расчетов демонстрируется влияние на относительное перемещение удлинения и площади энергосберегающих крыльев, а также эффект реализации относительного перемещения и вертикального ускорения при совместном использовании носового и кормового крыльев по сравнению со случаем использования только одного (носового или кормового) крыла. Полученные расчетные данные позволяют получить представление о механизме и эффективности снижения относительного перемещения на встречном волнении при качке судна с энергосберегающими крыльевыми элементами. Considered in the article are relative vertical displacement of the bow extremity of a ship with energy-saving wing elements in headwind regular waves, and also comparison of corresponding computational and experimental data. The method of calculation is based on a linear strip theory in frequency domain. At first, calculation is carried out of longitudinal (heaving & pitching) motions of a ship with and without wings in headwind waves, and then calculated results are employed to determine relative displacements of ship hull points. To account for the influence of inertial and damping effects of the wings attached to the hull we make use of Theodorsen theory of oscillating foil. Demonstrated in the course of calculations are the effects of wings aspect ratio and area as well as position with respect to the hull (bow wing, stern wing and bow & stern wings). Obtained computed data brings about better understanding of the mechanism and efficiency of reduction of vertical displacements of the hull points for a ship with energy-saving wings in headwind regular waves

scholarly journals To estimation of the Energy Efficiency Design Index (EEDI) for a ship with energy-saving wing devices

2021 ◽  
pp. 58-68
Author(s):  
К.В. Рождественский ◽  
М.Х. Зин
Keyword(s):  
Energy Efficiency ◽  
Aspect Ratio ◽  
Energy Saving ◽  
Wave Resistance ◽  
The Other ◽  
Large Aspect Ratio ◽  
Regular Waves ◽  
Strip Theory ◽  
Energy Efficiency Design Index ◽  
Oscillating Foil

В статье приводится оценка индекса проектной энергетической эффективности (EEDI) для судна с энергосберегающими крыльевыми устройствами на встречном регулярном волнении. Вначале на основе предыдущих работ авторов с применением линейной теории поперечных сечений определяются характеристики продольной (вертикальной и килевой) качки судна без крыльев, и такого же судна с крыльями большого удлинения, установленными на днище вблизи оконечностей с целью преобразования волновой энергии в дополнительную тягу. После определения параметров качки судна с крыльями как твердого тела, с применением теории Теодорсена колеблющегося профиля определяется средняя по периоду тяга энергосберегающих крыльевых элементов, совершающих поступательно-вращательные колебания. С другой стороны, в статье находится общее сопротивление системы «судно-крыльевые элементы». При этом применяется метод Холтропа в сочетании с теорие Бейкельмана-Герритсмы. Последняя дает возможность произвести оценку дополнительного волнового сопротивления по найденным параметрам продольной качки судна с крыльями и без крыльев. Затем оценивается значение индекса проектной энергетической эффективности (EEDI) контейнеровоза, снабженного энергосберегающими крыльями на встречном волнении. Исследование показывает, что установка на днище крыльевых элементов может использоваться как один из способов сокращения выброса углекислого газа и уменьшения в соответствии с требованиями Международной морской организации ИМО, значения индекса EEDI для репрезентативных морских условий. In this paper an estimation is presented of the Energy Efficiency Design Index (EEDI) for a ship with energy-saving wing devices in headwind regular waves. At first, based on previous works of the authors, there are determined with use of linear strip theory the characteristics of longitudinal (heaving and pitching) motions of a ship without wings and identical ship equipped with wings of large aspect ratio fitted on the bottom near extremities for the purpose of converting wave energy into additional thrust. After motions of the ship with wings as a solid boy are determined Theodorsen theory of oscillating foil is applied to calculate period averaged thrust of energy-saving wing elements, performing combined heave-pitch oscillations. On the other hand, the paper addresses the problem of determining overall drag of the “wing-plus-wings” system with use of Holtrop method combined with Beikelmann-Gerritsma theory. The latter enables carrying out an estimation of additional wave resistance based on the calculated parameters of the ship longitudinal motions with and without wings. Then follows an estimation of the EEDI for a containership equipped with wings in headwind regular waves. The study shows that fitting wing elements on the ship bottom can be seen as one of the methods for decreasing the magnitude of the EEDI for representative sea conditions as per requirements of the International Maritime Organization.

scholarly journals Ship Motions in Shallow Water As the Base for a Probabilistic Approach Policy

2008 ◽  
Author(s):  
Marc Vantorre ◽  
Erik Laforce ◽  
Katrien Eloot ◽  
Jan Richter ◽  
Jeroen Verwilligen ◽  
...  
Keyword(s):  
Shallow Water ◽  
Probabilistic Approach ◽  
Ship Motions ◽  
Wave Spectra ◽  
Fluid Mud ◽  
Response Functions ◽  
Regular Waves ◽  
Directional Wave ◽  
Probabilistic Criteria ◽  
Selection Of

A calculation tool has been developed for determining tidal windows for deep-drafted ships approaching and leaving the Belgian harbors according to probabilistic criteria. The calculations are based on a database containing response functions for the vertical motions in waves and squat data for a selection of representative ships. The database contains both results of model tests carried out in the Towing tank for maneuvers in shallow water – co-operation Flanders Hydraulics Research & Ghent University in Antwerp (Belgium), as well as calculated values. During the experiments, draft, trim, under keel clearance (7 to 20% of draft) and speed have been varied. The tests were performed in regular waves with lengths which are small compared to ship length, and in wave spectra that are typical for the Belgian coastal area. For given input data (ship characteristics, speed, tide, directional wave spectra, bottom, trajectory, current, departure time), the tool calculates the probability of bottom touch during the transit, so that a tidal window can be determined. Other restrictions, such as penetration into fluid mud layers and current, are taken into account as well.

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.

scholarly journals On the Comparative Seakeeping Analysis of the Full Scale KCS by Several Hydrodynamic Approaches

2020 ◽  
Vol 8 (12) ◽  
pp. 962
Author(s):  
Florin Pacuraru ◽  
Leonard Domnisoru ◽  
Sandita Pacuraru
Keyword(s):  
Global Economy ◽  
Domain Boundary ◽  
Ship Motions ◽  
Ocean Engineering ◽  
Regular Waves ◽  
Transport Channel ◽  
Navier Stokes Equation ◽  
Seakeeping Performance ◽  
Strip Theory ◽  
Head Waves

The main transport channel of the global economy is represented by shipping. Engineers and hull designers are more preoccupied in ensuring fleet safety, the proper operation of the ships, and, more recently, compliance with International Maritime Organization (IMO) regulatory incentives. Considerable efforts have been devoted to in-depth understanding of the hydrodynamics mechanism and prediction of ship behavior in waves. Prediction of seakeeping performances with a certain degree of accuracy is a demanding task for naval architects and researchers. In this paper, a fully numerical approach of the seakeeping performance of a KRISO (Korea Research Institute of Ships and Ocean Engineering, Daejeon, South Korea) container ship (KCS) container vessel is presented. Several hydrodynamic methods have been employed in order to obtain accurate results of ship hydrodynamic response in regular waves. First, an in-house code DYN (Dynamic Ship Analysis, “Dunarea de Jos” University of Galati, Romania), based on linear strip theory (ST) was used. Then, a 3D fully nonlinear time-domain Boundary Element Method (BEM) was implemented, using the commercial code SHIPFLOW (FLOWTECH International AB, Gothenburg, Sweden). Finally, the commercial software NUMECA (NUMECA International, Brussels, Belgium) was used in order to solve the incompressible unsteady Reynolds-averaged Navier–Stokes equation (RANSE) flow at ship motions in head waves. The results obtained using these methods are represented and discussed, in order to establish a methodology for estimating the ship response in regular waves with accurate results and the sensitivity of hydrodynamical models.

Some Extensions of the Classical Approach to Strip Theory of Ship Motions, Including the Calculation of Mean Added Forces and Moments

1978 ◽  
Vol 22 (01) ◽  
pp. 1-19 ◽  
Author(s):  
Theodore A. Loukakis ◽  
Paul D. Scfavounos
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Dynamical Theory ◽  
Forced Oscillations ◽  
Ship Motions ◽  
Regular Waves ◽  
Strip Theory ◽  
Calm Water ◽  
Exciting Forces ◽  
New Formulation

The application of the dynamical theory to the problem of a ship moving with constant forward speed on a free surface has been extended to include the exciting forces in oblique regular waves. As a result, it has become possible to derive a new formulation for the equations of motion, for a ship moving with five degrees of freedom. The application of the same theory has yielded formulas for the calculation of the mean added resistance and drift force in oblique regular waves and the calculation of all mean forces and moments for the forced oscillations of a ship in calm water.

Large-Scale Wave Kinematics Measurements of Regular Waves and Large-Amplitude Wave Groups

2010 ◽  
Author(s):  
Lisa Minnick ◽  
Christopher Bassler ◽  
Scott Percival ◽  
Lauren Hanyok
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Near Field ◽  
Field Measurements ◽  
Primary Objective ◽  
Irregular Waves ◽  
Ship Motions ◽  
Regular Waves ◽  
Wave Groups ◽  
Wave Kinematics

An experiment was performed to measure and characterize wave kinematics in an experimental basin. The experiment is part of an ongoing effort to improve predictions and measurements of ship motions in waves, including more accurate characterization of the near-field wave environment and its influence on ship motions. The primary objective of this experiment was to measure and characterize the wave kinematics of regular waves of varying steepness and scaled irregular seaways, including irregular waves with embedded wave groups. Measurements, including free-surface elevations and velocity field measurements under the free surface, are presented and discussed.

Linear Hydroelastic Analysis of High-Speed Catamarans and Monohulls

1999 ◽  
Vol 43 (01) ◽  
pp. 48-63
Author(s):  
Ole Andreas Hermundstad ◽  
Jan Vidar Aarsnes ◽  
Torgeir Moan
Keyword(s):  
High Speed ◽  
Hydrodynamic Interaction ◽  
Linear Method ◽  
Mode Shapes ◽  
Ship Motions ◽  
Regular Waves ◽  
Integral Theorem ◽  
Strip Theory ◽  
Theoretical Predictions ◽  
Hydroelastic Analysis

A linear method for hydroelastic analysis of high-speed vessels is presented. It is based on a modal approach and represents a generalization of the high-speed strip theory of Faltinsen & Zhao (1991a). Hydrodynamic interaction between the hulls of catamarans is properly accounted for by utilizing symmetry. It is demonstrated how an integral theorem can be utilized to find the hydrodynamic force for general mode shapes. Theoretical predictions of ship motions and sectional forces and moments are compared with experimental data for a flexible high-speed catamaran model in regular waves. The influences of hull interaction and the application of the integral theorem are demonstrated.

scholarly journals Time Scale for Scour Beneath Pipelines Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Current

2021 ◽  
Vol 9 (2) ◽  
pp. 114
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Time Scale ◽  
Current Flow ◽  
Irregular Waves ◽  
Wave Crest ◽  
Random Wave ◽  
Random Waves ◽  
Flow Conditions ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D

This article derives the time scale of pipeline scour caused by 2D (long-crested) and 3D (short-crested) nonlinear irregular waves and current for wave-dominant flow. The motivation is to provide a simple engineering tool suitable to use when assessing the time scale of equilibrium pipeline scour for these flow conditions. The method assumes the random wave process to be stationary and narrow banded adopting a distribution of the wave crest height representing 2D and 3D nonlinear irregular waves and a time scale formula for regular waves plus current. The presented results cover a range of random waves plus current flow conditions for which the method is valid. Results for typical field conditions are also presented. A possible application of the outcome of this study is that, e.g., consulting engineers can use it as part of assessing the on-bottom stability of seabed pipelines.

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