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1
Content available Effects of sway and roll excitations on sloshing loads in a KC-1 membrane LNG tank
An Se-yeol, Jeong Hyeon-won, Kim Ohyoung, Shim W. Jaewoo
Polish Maritime Research
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2023
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nr 4
43--53
EN
This study investigates the effects of sway and roll excitations on sloshing liquid loads in a tank, using Ansys Fluent software. The model considered in the study is a 1:50 scaled membrane-type tank, based on a KC-1 membrane LNG tank designed by Korea Gas Corporation (KOGAS). The volume of fluid (VOF) method is used to track the free surface inside the tank, and the standard k-ε model is applied to express the turbulent flow of the liquid. To explore the motion of the tank under excitation, a user-defined function (UDF) and a dynamic mesh technique are employed to control the external forces exerted on the tank through its motion. The results, in the form of time series data on the sloshing pressures in the tank under pure sway, roll, and coupled sway-roll, are analysed, with specific ranges for the excitation amplitudes and frequencies. We show that variations in excitation frequency and amplitude significantly influence the sloshing loads. Sloshing loads are found to intensify when the excitation frequency matches the tank’s primary natural frequency, 1.0 ω'1. Furthermore, with coupled sway-roll excitations, the sloshing loads are weakened when the sway and roll are in-phase and are intensified when these are out-of-phase. Fast Fourier transform analysis provides insights into the frequency domain, showing that the dominant frequency is 0.88 Hz and it is approximately equal to the tank’s primary natural frequency, 1.0 ω'1.
2
Content available Liquid vibrations in cylindrical tanks with and without baffles under lateral and longitudinal excitations
Strelnikova E., Kriutchenko D., Gnitko V., Tonkonozhenko A.
International Journal of Applied Mechanics and Engineering
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2020
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Vol. 25, no. 3
117--132
EN
The paper is devoted to issues of estimating free surface elevations in rigid cylindrical fluid-filled tanks dunder external loadings. The possibility of baffles installation is provided. The liquid vibrations caused by lateral and longitudinal harmonic loadings are under consideration. Free, forced and parametrical vibrations are examined. Modes of the free liquid vibrations are considered as basic functions for the analysis of forced and parametric vibrations. The modes of the free liquid vibrations in baffled and un-baffled cylindrical tanks are received by using single-domain and multi-domain boundary element methods. Effects of baffle installation are studied. The problems of forced vibrations are reduced to solving the systems of second order ordinary differential equations. For parametric vibrations the system of Mathieu equations is obtained. The numerical simulation of free surface elevations at different loadings and baffle configurations is accomplished. Beat phenomena effects are considered under lateral harmonic excitations. The phenomenon of parametric resonance is examined under longitudinal harmonic excitations.
3
Content available Experimental investigation of moonpool shapes on a ship with forward speed
Sajjan Sharanabasappa C., Surendran S.
Annual of Navigation
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2019
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No. 26
151--162
EN
A moonpool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch. A floating platform with a moonpool is subjected to different forces due to sloshing and movement of the entrapped fluid in it, while the body is subjected to environmental loads like waves, winds, currents etc.,. Inside a moonpool considerable relative motions may occur, depending on shape and depth of the moonpool and the frequency range of the waves to which it is exposed. The vessel responses are entirely different in zero and non-zero Froude numbers. Later situation is paid attention in this study. There will be different water column elevations in the moonpool depending on the shapes. Two modes of responses are possible based on the shape of the moonpool viz., piston mode for square and sloshing mode for rectangular shape. An aspect ratio of 1:1 for square, 1:1.5 and 1:2 in case of rectangular shapes is considered during experimentation. Circular shaped moonpool is also tested for finding the response. The vessel is initially tested in a towing tank with different drafts and speeds based on Froude scaling. The different modes of oscillations of water column are measured using wave gauge and the vessel resistance is also studied, with and without moonpool. The water column elevation in moonpool may provide better insight to the designer to consider operational and safety parameters.
4
Content available Wave-based attitude control of spacecraft with fuel sloshing dynamics
Thompson J. W., O'Connor W.
Archive of Mechanical Engineering
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2016
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Vol. LXIII, nr 2
263--275
EN
Wave-Based Control has been previously applied successfully to simple underactuated flexible mechanical systems. Spacecraft and rockets with structural flexibility and sloshing are examples of such systems but have added difficulties due to nonuniform structure, external disturbing forces and non-ideal actuators and sensors. The aim of this paper is to extend the application of WBC to spacecraft systems, to compare the performance of WBC to other popular controllers and to carry out experimental validation of the designed control laws. A mathematical model is developed for an upper stage accelerating rocket moving in a single plane. Fuel sloshing is represented by an equivalent mechanical pendulum model. A wave-based controller is designed for the upper stage AVUM of the European launcher Vega. In numerical simulations the controller successfully suppresses the sloshing motion. A major advantage of the strategy is that no measurement of the pendulum states (sloshing motion) is required.
PL
Sterowanie oparte na podejściu falowym było w przeszłości stosowane z powodzeniem do prostych, elastycznych systemów mechanicznych, w których liczba sygnałów sterujących jest mniejsza od liczby stopni swobody. Rakiety i statki kosmiczne, strukturalnie elastyczne, w których występuje zjawisko przelewania się płynu, są przykładami takich systemów, lecz nastręczają dodatkowe trudności z powodu niejednorodnej struktury, zewnętrznych sił zakłócających i nieidealnych elementów wykonawczych i czujników. Celem pracy jest zastosowanie sterowania opartego na podejściu falowym (WBC) do systemów statków kosmicznych, porównanie efektów strategii WBC z działaniem innych popularnych regulatorów i eksperymentalne potwierdzenie poprawności opracowanych praw sterowania. Opracowano model matematyczny dla górnego stopnia rakiety przyspieszającej poruszającej się w pojedynczej płaszczyźnie. Przelewanie się płynu jest reprezentowane przez równoważny model wahadła mechanicznego. Układ sterujący typu WBC został zaprojektowany dla górnego stopnia AVUM europejskiej rakiety nośnej Vega. Symulacja numeryczna wykazała, że układ sterowania z powodzeniem tłumi ruchy wywołane przelewaniem się płynu. Zaletą tej strategii jest, że nie są wymagane żadne pomiary stanów wahadła (ruchów przelewającego się płynu).
5
Content available Linear characteristics of the sloshing phenomenon for the purpose of on-board ship’s stability assessment
Krata P.
Journal of Theoretical and Applied Mechanics
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2009
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Vol. 47 nr 2
307-320
EN
The paper presents results of experimental research and numerical simulations of the sloshing phenomenon. The research was focused on computation of the heeling moment affecting stability of a vessel. The proposed linearisation enables application of the results to the asses- sment of the ship’s stability. The dependence of the heeling moment upon localisation of a tank in the ship’s hull is analysed. The heeling moment obtained in the course of the research was compared to the moment computed in accordance with the Intact Stability Code requirements. The study may be a contribution to the more sophisticated estimation of the ship’s stability than it is achieved nowadays.
PL
Artykuł prezentuje wyniki badań eksperymentalnych i symulacji numerycznych ruchu cieczy w niepełnych zbiornikach statku. Istostą badań było wyznaczenie momentu przechylającego statek wskutek ruchu cieczy w zbiornikach, co wpływa na stateczność poprzeczną statku. Zaproponowana metoda linearyzacji momentu umożliwia implementację wyników badań przedmiotowego zjawiska do praktyki oceny stateczności poprzecznej statku. Szczególną uwagę zwrócono na zależność pomiędzy momentem przechylającym statek a lokalizacją niepełnego zbiornika względem osi kołysań bocznych. Zarazem wyznaczany moment przechylający został porównany do quasi-statycznego momentu wyliczonego zgodnie z zaleceniami Kodeksu ISC. Przeprowadzone badania mogą stanowić element poprawy wiarygodności oceny stateczności statku dokonywanej ru- tynowo przez oficerów ładunkowych.
6
Content available Ship's heeling moment due to liquid sloshing in tanks - 3D attitude
Jachowski J., Krata P.
Journal of KONES
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2009
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Vol. 16, No. 2
191-197
EN
The matter of the paper refers to the dynamic stability of a vessel as an important factor affecting her safety at seaway. Ship 's seakeeping behaviour, which comprises the notion of her stability, is one of the researched key issues leading to the increase in understanding of the safety qualifying factors. Liquid sloshing phenomenon is a result of partly filled tank motions. As a tank moves, it supplies the energy to induce and sustain the fluid motion. The dynamic behaviour of a vessel at seaway is considerably affected by the dynamics of free liquid surfaces, therefore the influence of fluid movement taking place in partly filled tanks on the safety of ship 's exploitation process is emphasized. The paper presents the results of the experimental research and the numerical simulation of the sloshing phenomenon. The research was focused on the computation of the heeling moment affecting the stability of a vessel, especially dynamic effects, which are omitted in obligatory intact ship 's stability regulations nowadays. The experiment performed in the course of the research was carried out in Department of Ship Operation at Gdynia Maritime University. The unique test apparatus was designed and built. It enables to measure dynamic pressures on model tank walls for large oscillation amplitudes, which are characteristic for stormy sea conditions. The numerical simulations of liquid sloshing phenomenon, took into account the viscosity of liquid and the turbulence of considered flows. All the simulations were computed in 3D mode and they provide high accuracy results. The spatial distribution of dynamic pressures on model tank walls enables computation of heeling moment due to liquid sloshing which affects ship 's stability. Further analysis of obtained moments was carried out. The study may be the contribution to the more sophisticated estimation of the ship's stability than it is achieved nowadays.
7
Content available The dynamic free surface effect for different locations of partly filled tanks on board ships
Krata P.
Problemy Eksploatacji
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2008
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nr 1
171-179
EN
The results of experimental research and numerical simulation of sloshing phenomenon are presented. The heeling moment due to the dynamic movement of the fluid in a partly filled ship's tank is computed. The dependence of heeling moment effects upon the locations of the tank in the hull is described.
PL
W artykule przedstawiono wyniki badań eksperymentalnych i symulacji numerycznych w zakresie przebiegu momentu przechylającego statek wskutek ruchu cieczy w niepełnych zbiornikach. Uwagę zwrócono na wpływ położenia niepełnego zbiornika względem osi kołysań bocznych statku.
8
Content available remote Doświadczalna lokalizacja rejonów maksymalnego oddziaływania cieczy poruszającej się dynamicznie w częściowo zapełnionych okrętowych zbiornikach dennych
Krata P.
Zeszyty Naukowe Akademii Marynarki Wojennej
|
2006
|
R. 47 nr 166K/1
249-270
PL
Przedmiotem badań opisanych w niniejszym opracowaniu jest dynamiczne oddziaływanie cieczy na ściany poruszającego się zbiornika częściowo zapełnionego. Omówiona ostała konstrukcja stanowiska pomiarowego, założenia pomiarowe, zakres modelowanych zjawisk. Rezultatem badań jest lokalizacja rejonów maksymalnych oddziaływań dynamicznie poruszającej się cieczy w zbiornikach częściowo zapełnionych. Uzyskane wyniki umożliwiają identyfikację miejsc o największym zagrożeniu wytrzymałościowym wynikającym, z lokalnych obciążeń dynamicznych. Zaproponowano również kierunek dalszych badań zmierzających do prawy bezpieczeństwa statków poprzez eliminację awarii związanych ze zjawiskiem sloshingu.
EN
The research described in this paper is the dynamic interaction of the liquid on a moving wall of the container partially filled up. Discussed design survived a test stand, test assumptions, the extent of the modeled phenomena. The result is a localization of areas of maximum impacts dynamically moving liquids in partially filled tanks. The results allow identification of the highest durability under threat, the local dynamic loads. Has also been suggested directions for further research aimed at the right ship safety by eliminating failures related to the phenomenon sloshingu.
9
Ship motion affected by moving liquid cargo in holds
Warmowska M., Jankowski J.
Systems : journal of transdisciplinary systems science
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2006
|
Vol. 11, nr 1
117-124
EN
Liquid cargo moving in holds (sloshing) of a ship sailing in waves affects ship motion. Sloshing forces are taken into account in the equations of ship motion. The motion of liquid cargo in ship holds is described by boundary value problems in which the essential element is the moving free surface of the liquid. This problem is solved by Boundary Element Method. This paper presents the analysis of ship motion effected by moving molten sulphur in partly filled holds. The analysis has been carried out for different regular and irregular waves inducing ship motion coupled with sloshing. A numerical solution of the sloshing boundary-value problem and the equations of ship motion make it possible to develop a visualization of the ship motion in waves.
10
Content available Numerical simulation of liquid motion in a partly filled tank
Warmowska M.
Opuscula Mathematica
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2006
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Vol. 26, no. 3
529-540
EN
The paper presents the problem of liquid motion in a 2D partly filled tank. It is assumed that the flow of liquid in tank is a potential, hence it can be described by Laplace equations with appropriate boundary conditions. The problem is solved using the boundary element method. The developed numerical algorithm makes it possible to determine the free surface elevation, the velocity field and the pressure field during the liquid motion in the tank. The area occupied by liquid is represented by a mesh changing in time. Numerical computations are performed for translatory and rotational motion of the tank. The results of numerical computations are verified by experiment.
11
Content available remote Liquid sloshing excited by pressure on a sport of a free Surface
Cattani C., Konstantinov A.
Vibrations in Physical Systems
|
2002
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Vol. 20
208--209
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