Wyniki wyszukiwania - Biblioteka Nauki

1

An approach to optimization of ship design parameters with accounting for seakeeping ability

100%

Szelangiewicz T. , Cepowski T.

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tom Vol. 9, nr 4

8-16

EN

In the paper a method, using a genetic algorithm, of searching optimum ship design parameters which satisfy economical and technical criteria with accounting for seakeeping ability, was presented. To assess seakeeping ability of a ship in waves the ship operational effectiveness factor E was applied. An example of application of the approach is attached and discussed.

2

Application of Artificial Neural Networks to investigations of ship seakeeping ability. Part I

80%

Cepowski T. , Szelangiewicz T.

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tom Vol. 8, nr 3

11-15

EN

In order to optimize the ship design at its conceptual and preliminary stages with taking into account also seakeeping criteria, simple and simultaneously exact relationships between the basic ship design parameters and seakeeping ability are necessary. The wave-induced motions of the ship in irregular waves as well as phenomena accompanying the moations, are determined on the basis of the frequency transfer functions of the ship motions in regular waves. In this paper an approximation method is presented for determination of such transfer functions with the use of the Artificial Neural Networks (ANNs). The attached results of numerical calculations show that the method provides exact data for ships of very different sizes, within wide ranges of ship velocity and direction of wave relative to the ship.

3

Application of Artificial Neural Networks to investigations of ship seakeeping ability. Part II

80%

Cepowski T. , Szelangiewicz T.

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tom Vol. 8, nr 4

26-29

EN

In order to optimize the ship design at its conceptual and preliminary stages with taking into account also seakeeping criteria, simple and simultaneously exact relationships between the basic ship design parameters and seakeeping ability are necessary. The wave-induced motions of the ship in irregular waves as well as phenomena accompanying the motions, are determined on the basisi of the frequency transfer functions of the ship motions in regular waves. in this paper an approximation method is presented for determinational of such transfer functions with the use of the Artificial Neural Networks (ANNs). The attached results of numerical calculations show that the method provides exact data for ships of very different sizes, within wide ranges of ship velocity and direction of wave relative to the ship.

4

Prediction of ship motions in irregular waves based on response amplitude operators evaluated experimentally in noise waves

70%

Bielicki S.

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2021

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tom nr 1

16--27

EN

The most common methods for predicting ship roll motions in a specified sea state are direct measurements of motions in a representative irregular wave realisation (time domain) or calculations of motions from response amplitude operators (RAOs) in the frequency domain. The result of the first method is valid only for the tested sea state, whilst the second method is more flexible but less accurate. RAO-based predictions are calculated assuming a linear model of ship motions in waves. RAO functions are usually evaluated by means of tests in regular waves for a limited number of frequencies and a constant wave amplitude. This approach is time-consuming and the discrete form of the RAO functions obtained for a limited number of frequencies may lead to discrepancies in the prediction of seakeeping and often does not allow the actual amplitude of the response in resonant frequency to be determined. Another challenge is the appropriate selection of wave amplitude for tests due to the considerable influence of viscous damping on roll response in irregular sea waves. There are alternative methods for the experimental determination of RAO functions and one of them is presented in this study. The presented approach allows RAO functions to be evaluated in one run by the generation of irregular waves characterised by a white or coloured noise spectrum. This method reduces the experiment duration, with almost continuous RAO characteristics obtained. The flat (white noise) and linear (coloured noise) wave spectral energy characteristics are considered in the experiment and the obtained predictions are compared with the results of accurate measurements in irregular waves.

5

Numerical and experimental analysis of the wave induced forces on the tripod support structure. Laboratory study

60%

Kraskowski M. , Pastwa K. , Kowalczyk S. , Marcinkowski T.

Biuletyn Instytutu Morskiego w Gdańsku

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2017

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tom Vol. 32, No. 1

21--29

EN

The presented work was realized within the framework of the AQUILO project, aiming to create the base of knowledge for prospective future investments in offshore wind energy on the Baltic Sea. The presented part of the work is focused on the experimental validation of numerical method of evaluation of the wave-induced forces on the bottom-mounted support structure of the offshore wind turbine. The experimental setup and measurement equipment, including in-house developed 6-DOF (six freedom) dynamometer, are described. Comparison of performance of different methods of evaluation of wave loads for wide range of parameters is presented. The results of experiments and numerical analyses are consistent; the largest discrepancy occurred at lowest wave frequencies, i.e., largest wave lengths. This may result from increased relative error of measurements for long waves in a relatively short tank.

PL

Prezentowana praca została wykonana w ramach projektu AQUILO, mającego na celu stworzenie bazy wiedzy dla przyszłych, potencjalnych inwestycji w energetykę wiatrową na akwenach Morza Bałtyckiego. W prezentowanej pracy wykonano empiryczną walidację numerycznej metody wyznaczania obciążeń falowych działających na konstrukcję wsporczą morskiej elektrowni wiatrowej. Przedstawiono i opisano fizyczny model doświadczalny oraz urządzenia pomiarowe, włącznie z wykonanym dla tego zadania dynamometrem o sześciu stopniach swobody (6 DOF). Zaprezentowano porównanie wyników obciążeń wywołanych falowaniem, otrzymanych różnymi metodami, dla szerokiego zakresu zmienności parametrów falowania. Wyniki uzyskane z przeprowadzonych doświadczeń oraz wyniki otrzymane z modelu numerycznego wykazują zadowalającą zgodność; największe rozbieżności wystąpiły dla częstotliwości najniższych, tj. dla fal najdłuższych. Przyczynę tych rozbieżności można tłumaczyć wzrostem względnego błędu pomiarowego dla bardzo długich fal w stosunkowo krótkim basenie.

6

Numerical simulation of the seakeeping of a military trimaran hull by a novel overset mesh method in regular and irregular waves

60%

Ghadimi P. , Karami S. , Nazemian A.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2021

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tom nr 65 (137)

38--50

EN

The hydrodynamic performance of trimaran hulls has been previously investigated for optimum performance in calm water, but there is still a limited understanding of its motion response; therefore, a CFD-based numerical approach was developed and applied on a trimaran hull in the presence of regular and irregular waves. To validate the CFD method, a comparison was conducted using both experimental and 3D panel method data. In this study, two different turbulence models were surveyed, and the SST Menter k-Omega (k-ω) turbulence model was shown to be a more accurate model than the realizable k-Epsilon (k-ε) model. The different features of the proposed numerical model include the implementation of an overset mesh method, unique mesh plan refinement, and wave-damping region. The discrepancy between the experimental data and the results of other seakeeping calculation methods have always been problematic, especially for low-speed strip theory and 3D panel methods, but good consistency was observed between the proposed CFD model and experimental data. Unlike potential-based or conformal mapping seakeeping analysis methods, the effect of nonlinear waves, hull shape above the waterline, and other ship dynamic phenomena were considered in this CFD application. The proposed CFD method reduces the simulation time and computational efforts for ship motion calculations.

7

Aproksymacja kołysań bocznych kontenerowca S-175 na fali nieregularnej oparta na parametrach eksploatacyjnych statku

41%

Cepowski T.

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tom nr 6 (78)

65-75

PL

Przedstawiono aproksymację kołysań bocznych kontenerowca S-175 na fali nieregularnej opartą na parametrach eksploatacyjnych statku. Wartości wzorcowe kołysań bocznych obliczono dokładnymi metodami numerycznymi za pomocą programu SEAWAY. Funkcję aproksymacyjną opracowano za pomocą sztucznych sieci neuronowych i przedstawiono w postaci analitycznej. Prezentowana metodyka może pozwolić na prognozowanie rzeczywistych wartości kołysań bocznych, opartych na danych zarejestrowanych na statku.

EN

The paper presents approximations of roll amplitudes of a S-175 containershipoccurring in irregular waves on the basis of main service parameters. Standard values of ship's roll were determined by means of exact numerical methods by using the SEAWAY software. The relationships were elaborated by means of artificial neural networks and presented as an analytical function. The proposed approach may be used to approximate real values of roll angle amplitude on the basis of data recorded onboard the ship during its service.

8

Seakeeping software for the analysis of a ship’s seaworthiness

41%

Cepowska Ż. , Cepowski T.

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2015

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tom nr 42 (114)

95--100

EN

The article presents the Seakeeping research software, developed for the computation of a ship’s motions in regular and irregular waves on the basis of the following ship parameters: length between perpendiculars, beam, draught, block coefficient and transverse initial metacentric height. The software implements approximating functions of amplitude-phase characteristics of rolling, heaving, and pitching, developed by the author by means of artificial neural networks. The software determines transfer functions for the phenomena accompanying the rolling motion, such as slamming, green water, propeller surfacing, vertical acceleration forward and on the bridge. The article discusses possible uses of the software in scientific research, ship design and operation, and for educational purposes.