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1

Low frequency sloshing analysis of cylindrical containers with flat and conical baffles

Gnitko V., Naumemko Y., Strelnikova E.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 4

867--881

EN

This paper presents an analysis of low-frequency liquid vibrations in rigid partially filled containers with baffles. The liquid is supposed to be an ideal and incompressible one and its flow is irrotational. A compound shell of revolution is considered as the container model. For evaluating the velocity potential the system of singular boundary integral equations has been obtained. The single-domain and multi-domain reduced boundary element methods have been used for its numerical solution. The numerical simulation is performed to validate the proposed method and to estimate the sloshing frequencies and modes of fluid-filled cylindrical shells with baffles in the forms of circular plates and truncated cones. Both axisymmetric and non-axisymmetric modes of liquid vibrations in baffled and un-baffled tanks have been considered. The proposed method makes it possible to determine a suitable place with a proper height for installing baffles in tanks by using the numerical experiment.

2

Dynamic response of a base-isolated concrete rectangular liquid-storage structure under large amplitude sloshing

Cheng X., Li D., Li P., Zhang X., Li G.

Archives of Civil Engineering

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2017

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Vol. 63, nr 1

33--45

EN

Considering concrete nonlinearity, the wave height limit between small and large amplitude sloshing is defined based on the Bernoulli equation. Based on Navier-Stokes equations, the mathematical model of large amplitude sloshing is established for a Concrete Rectangle Liquid-Storage Structure (CRLSS). The results show that the seismic response of a CRLSS increases with the increase of seismic intensity. Under different seismic fortification intensities, the change in trend of wave height, wallboard displacement, and stress are the same, but the amplitudes are not. The areas of stress concentration appear mainly at the connections between the wallboards, and the connections between the wallboard and the bottom.

PL

Gdy amplituda chlupotania cieczy jest zbliżona do częstotliwości drgań struktury magazynowania substancji ciekłych (CRLSS), wówczas osiągamy rezonans i możemy zaobserwować silne zjawisko nieliniowe. Szkoda jest znacznie większa niż chlupotanie o małej amplitudzie. Obecnie brak jest odpowiedniego raportu na temat badań dynamicznej odpowiedzi struktury magazynowania substancji ciekłych z wykorzystaniem betonu izolacyjnego (CRLSS) z chlupotaniem o dużej amplitudzie, a wpływ materiałów betonowych nie jest brany pod uwagę. W związku z tym, w niniejszej pracy, w oparciu o równanie Bernoulliego, otrzymano ograniczone wysokości fali o dużej amplitudzie chlupotania oraz małej amplitudzie chlupotania. Na podstawie równań Naviera-Stokesa ustanowiono matematyczny model chlupotania o dużej amplitudzie i zbadano odpowiedź sejsmiczną CRLSS podczas chlupotania o dużej amplitudzie. Rozważając równanie Bernoulliego i zadowalający stan, chlupotanie substancji ciekłej jest liniowe, a nieliniowy kwadratowy człon jest lekceważony. W stałym i płynnym interfejsie, struktura magazynowania substancji ciekłych spełnia warunki ciągłości przemieszczania i równowagi siły oddziaływań. Właściwość mechaniczna gumowego zabezpieczenia izolacyjnego została opisana w oparciu o konstytutywną relacje modelu Mooney-Rivlin.

3

A Method of Assessment of the Liquid Sloshing Impact on Ship Transverse Stability

Krata P.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2014

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Vol. 8 no. 4

535--541

EN

Liquid sloshing phenomenon taking place in partly filled ships’ tanks directly affects the stability of a vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation. The paper is focused on a dynamic heeling moment due to liquid sloshing in tanks onboard ships. The set of numerical simulations of liquid sloshing taking place in moving tanks is carried out. The realistic range of geometric parameters is taken into account. The conducted CFD simulations are experimentally verified. Finally, the method of an assessment of the liquid sloshing impact on ship transverse stability is worked out. The key point of the method is a dynamic coefficient describing relation of the researched dynamic heeling moment and the quasi-static one in terms of dynamic stability of a vessel which is related to the weather criterion of ship stability assessment.

4

Analysis of dynamic heeling moment due to liquid sloshing in partly filled ship's tanks for realistic range of rolling periods - a case study

Jachowski J., Krata P., Wawrzyński W., Więckiewicz W.

Journal of KONES

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2012

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Vol. 19, No. 3

177-184

EN

Liquid sloshing phenomenon is a result of partly filled tank motions. As a tank moves, it supplies energy to induce and sustain a fluid motion. Both the liquid motion and its effects are called sloshing. The interaction between ship’s tank structure and water sloshing inside the tank consists in the constant transmission of energy. As the ship rolls, the walls of a partly filled tank induce the movement of water. Liquid sloshing phenomenon occurring in partly filled ships tanks directly affects the stability of the vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation and assessment. Since previous researches reveal the necessity of dynamic approach towards liquid movement onboard ships, the investigation is focused on problems related to time dependent wave-type phenomena. This aspect is omitted in the course of standard ship stability calculations. The set of numerical simulations of liquid sloshing taking place in moving tanks is carried out. Among many obtained characteristics, the heeling moment due to sloshing is emphasized and thoroughly investigated. The realistic range of possible metacentric heights and rolling periods is examined. The influence of ship’s rolling period on the heeling moment due to liquid sloshing is analyzed for one exemplary seagoing vessel as a case study. However, the conclusions can be generalized to some degree and comprise many other ships.

5

An investigation into the influence of tank filling level on liquid sloshing effects onboard ships – static and dynamic approach

Krata P., Wawrzyński W., Jachowski J., Więckiewicz W.

Journal of KONES

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2012

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Vol. 19, No. 3

239-248

EN

The commonly discussed main features of maritime transport are usually its safety and effectiveness. One of the most critical features of seagoing ships related to her safety is stability influencing ship's overall sea keeping performance. Vessels' stability calculation and evaluation, made on-board nowadays, is based on the stability criteria published by the ship’s classification societies. According to the IMO recommendations, the righting lever curve should be corrected for the effect of free surfaces of liquids in tanks. IMO-recommended methods of free surface correction calculation consider the static attitude towards the liquid sloshing phenomenon only. They also do not consider the location of the tank within the hull of the ship and the location of a rolling axis. The more precise and more realistic approach towards liquid movement is complex analysis of liquid sloshing phenomenon. As liquid sloshing taking part in partly filled ship's tanks is an important element affecting safety of maritime transportation process, there is a need for detailed analyses related to crucial parameters of the considered phenomenon. The paper is focused on an influence of tank's filling level on effects of aroused and sustained movement of ballast water, fuel and other liquids carried onboard ships. Both static and dynamic approaches towards the problem are utilized. The analytical methods for liquid weight transfer calculation and numerical simulations of the liquid sloshing phenomenon are applied. The simulations of liquid sloshing are based on Reynolds-averaged Navier-Stockes equation and they take into account the viscosity of liquid. The resultant heeling moment is decomposed into components enabling extraction of dynamical component differentiating the applied method from old static ones. The results of the study contribute to more precise ship safety evaluation.

6

3D CDF modeling of ship's heeling moment due to liquid sloshing in tanks - a case study

Krata P., Jachowski J.

Journal of KONES

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2010

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Vol. 17, No. 4

245-251

EN

Modeling of liquid sloshing inside partly filled ships' tanks can be carried out by a variety of methods. The simplest and perhaps the less reliable is a quasi-static approach which is, however, recommended in the Intact Stability Code by the International Maritime Organization. Hence the only advantage of the static estimation of liquid sloshing is simplicity of calculations, the research into the application of CFD (Computational Fluid Dynamics) was performed in Department of Ship Operation at Gdynia Maritime University. The paper presents results of numerical simulations o f a liquid sloshing phenomenon performed by means of a code Fluent. The research was focused on a computation of the heeling moment affecting stability of a vessel, especially on the dynamic effects, which are omitted in obligatory intact ship's stability regulations nowadays. The computed distributions of dynamic pressures on tank walls were carried out for large oscillation amplitude which is characteristic for stormy sea conditions. Ali the simulations were computed in 3D mode and they provide high accuracy results. A case study described in the paper enables realistic comparison of the results of CFD liquid sloshing simulations and the simple statics based computations. The study reveals some weaknesses of the contemporary quasi-static approach towards the free surface effect and it might be the contribution to the more sophisticated estimation of the ship's stability than it is achieved nowadays.

7

Liquid sloshing excited by pressure on a sport of a free Surface

Cattani C., Konstantinov A.

Vibrations in Physical Systems

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2002

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Vol. 20

208--209