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1
Content available Experimental study and numerical simulation of the water entry of a ship-like symmetry section with an obvious bulbous bow
Wang Qiang, Yu Pengyao, Zhang Boran, Li Guangzhao
Polish Maritime Research
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2021
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nr 3
16--34
EN
A bulbous bow is a typical ship structure. Due to the influence of the bulbous bow, complex flow separation and gas capture phenomena may appear during the water entry of ship-like sections. In this paper, experimental and numerical studies on the water entry of a ship-like section with an obvious bulbous bow are carried out. Two thin plates are installed at both ends of the test model to ensure that the flow field during the impact process is approximately twodimensional. The free-fall drop test is carried out in the test rig equipped with guide rails. By changing drop heights, impact pressure on the model surface with different initial impact velocities is measured. A numerical model for simulating the water entry of the ship-like section is established by using the Computational Fluid Dynamics (CFD) method, based on the Navier-Stokes equations. Reasonable time steps and mesh size are determined by convergence analysis. Four different flow models are used in the numerical analysis. It is found that the K-Epsilon turbulence model can present the most reasonable numerical prediction by comparing numerical results with the experimental data. Furthermore, the influence of the bulbous bow on the impact loads is numerically studied by using the validated numerical model. It suggests that the bulbous bow has little effect on the impact force acting on the bow-flared area but, in the position near the bulbous bow, the pressure will be affected by the second slamming and the air cushion.
2
Content available Numerical simulation of cushioning problem for blunt bodies using boundary element method
Barjasteh M., Zeraatgar H.
Polish Maritime Research
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2018
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S 1
85--93
EN
Induced air pressure and resulting free surface profile due to air cushioning layer is studied. The study is mainly focused on 2D blunt circular bodies with constant downward speed. The problem is first solved for the air flow between the body and the free surface of the water. Then the results are employed to solve the problem for the water problem, numerically. Both air and water problem are assumed to be governed by Laplace potential equation. Depending on the induced pressure and velocity of the escaping air flow from cushioning layer, compressibility of the air is also included in the modeling. Gravitational acceleration is also included in the model. An iterative boundary element method is used for numerical solution of both air and water problems. Instantaneous pressure distribution and free surface profile are evaluated for different bodies. The results of calculation for large blunt bodies show that inviscid potential method can fairly approximate the problem for large blunt bodies. Additionally, the behavior of the air pressure for the very blunt body is impulsive and the magnitude of the peak pressure is in order of impact pressure of water entry. The obtained results are compared with analytical method. The comparison shows that as the bluntness of a body increases, the better agreement is concluded.
3
Content available Seakeeping software for the analysis of a ship’s seaworthiness
Cepowska Ż., Cepowski T.
Zeszyty Naukowe Akademii Morskiej w Szczecinie
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2015
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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.
4
Content available Modelling of seakeeping ability of FPSO vessels
Cepowski T.
Zeszyty Naukowe / Akademia Morska w Szczecinie
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2011
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nr 25 (97)
13-20
EN
Problems concerning preliminary design of FPSO vessels are presented in view of their seakeeping ability. The article analyzes the presently applied approach in which seakeeping quality of FPSO vessels is taken into consideration and discusses possibilities of using this approach at the preliminary stage of design. Besides, the current approach used for predicting such phenomena as heaving, slamming and green water loading is discussed.
PL
W artykule przedstawiono problematykę projektowania wstępnego statków FPSO, biorąc pod uwagę właściwości morskie tych statków. W artykule przeanalizowano aktualnie stosowane podejście, dotyczące uwzględniania właściwości morskich statków FPSO i możliwości wykorzystania tego podejścia na wstępnym etapie projektowania. W artykule przedstawiono aktualnie stosowane podejście do prognozowania m.in. nurzań, slemingu i zalewania pokładu statków FPSO.
5
Content available The modeling of seakeeping qualities of Floating Production, Storage and Offloading (FPSO) sea-going ships in preliminary design stage
Cepowski T.
Polish Maritime Research
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2010
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nr 4
3-12
EN
This paper presents an analysis of a presently applied approach to accounting for seakeeping qualities of FPSO sea-going ships and possible using it in preliminary design stage. Approximations of heaving, pitching, green water ingress on the deck and slamming of FPSO ships, based on main ship design and wave parameters, are presented. The approximations were elaborated with the use of the linear regression method and theory of artificial neural networks for a very wide range of FPSO ship dimensions and hull forms. In the investigations ship operational conditions were limited to those occurring in real service of FPSO ships, described by means of the so called operational scenario. Such approach made it possible to reach simultaneously high approximation accuracy and simple structure of mathematical model.
6
Content available remote Zastosowanie sztucznych sieci neuronowych do przewidywania slammingu
Cepowski T.
Napędy i Sterowanie
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2009
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R. 11, nr 2
103-106
PL
W pracy przedstawiono zastosowanie sztucznych sieci neuronowych do przewidywania slammingu przedstawionego za pomocą zmiennych lingwistycznych („mały”, „średni”, „duży” slamming). Badania przeprowadzono dla typowego masowca znajdującego się w balastowym stanie załadowania. Opracowane w postaci sztucznych sieci neuronowych funkcje analityczne przeanalizowano pod kątem dokładności w stosunku do wartości wzorcowych. Prezentowany algorytm może bazować na danych zgromadzonych na drodze obserwacji zachowania się statku na fali.
EN
This paper presents an application of artificial neural networks to estimation of slamming data presented by linguistic variables ("small", "medium" "large" slamming) The investigations were performed for a typical carrier in ballast loading condition. Analytical function presented in the form of artificial neural networks were analyzed with a view of their accuracy against standard values. The presented algorithm can be based On data collected through observation of the ship behaviour.
7
Zastosowanie sztucznych sieci neuronowych do oceny bezpieczeństwa w transporcie morskim
Cepowski T.
Logistyka
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2008
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nr 2
CD-CD
PL
W pracy przedstawiono zastosowanie sztucznych sieci neuronowych do rozpoznawania slammingu w zależności od parametrów ruchu statku i parametrów falowania. Analizę przeprowadzono dla typowego masowca znajdującego się w balastowym stanie załadowania. Badania przeprowadzono w oparciu o odpowiedzi statku obliczone dokładnymi metodami numerycznymi. Opracowane w postaci sztucznych sieci neuronowych funkcje analityczne przeanalizowano pod kątem dokładności w stosunku do wartości wzorcowych. Badano możliwości wykorzystania sztucznych sieci neuronowych pod kątem dokładności rozpoznawania założonych odpowiedzi statku.
EN
This paper presents an application of artificial neural networks to identification of slamming depending on ship motion and wave parameters. The analysis was performed for a typical bulk carrier in ballast loading conditions. The investigations were carried out on the basis of ship response data calculated by means of exact numerical methods. Analytical functions presented in the form of artificial neural networks were analyzed with a view of their accuracy against standard values. Possible ways of application of the artificial neural networks were examined from the point of view of accuracy of identification of the assumed ship response parameters.
8
Content available Approximation of the index for assessing ship sea-keeping performance on the basis of ship design parameters
Cepowski T.
Polish Maritime Research
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2007
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nr 3
21-26
EN
This paper presents a new approach which makes it possible to take into account seakeeping qualities of ship in the preliminary stage of its design. The presented concept is based on representing ship’s behaviour in waves by means of the so called operational effectiveness index. Presented values of the index were calculated for a broad range of design parameters. On this basis were elaborated analytical functions which approximate the index depending on ship design parameters. Also, example approximations of the index calculated by using artificial neural networks, are attached. The presented approach may find application to ship preliminary design problems as well as in ship service stage to assess sea-keeping performance of a ship before its departure to sea.
9
Content available Application of artificial neural networks to approximation and identification of sea-keeping performance of a bulk carrier in ballast loading condition
Cepowski T.
Polish Maritime Research
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2007
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nr 4
31-39
EN
This paper presents an application of artificial neural networks to approximation and identification of additional wave-generated resistance, slamming and internal forces depending on ship motion and wave parameters. The analysis was performed for a typical bulk carrier in ballast loading conditions. The investigations were carried out on the basis of ship response data calculated by means of exact numerical methods. Analytical functions presented in the form of artificial neural networks were analyzed with a view of their accuracy against standard values. Possible ways of application of the artificial neural networks were examined from the point of view of accuracy of approximation and identification of the assumed ship response parameters.
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