• Title/Summary/Keyword: sloshing

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Simple analytical method for predicting the sloshing motion in a rectangular pool

  • Park, Won Man;Choi, Dae Kyung;Kim, Kyungsoo;Son, Sung Man;Oh, Se Hong;Lee, Kang Hee;Kang, Heung Seok;Choi, Choengryul
    • Nuclear Engineering and Technology
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    • v.52 no.5
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    • pp.947-955
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    • 2020
  • Predicting the sloshing motion of a coolant during a seismic assessment of a rectangular spent fuel pool is of critical concern. Linear theory, which provides a simple analytical method, has been used to predict the sloshing motion in rectangular pools and tanks. However, this theory is not suitable for the high-frequency excitation problem. In this study, the authors developed a simple analytical method for predicting the sloshing motion in a rectangular pool for a wide range of excitation frequencies. The correlation among the linear theory parameters, influencing on excitation and convective waves, and the excitation frequency is investigated. Sloshing waves in a rectangular pool with several liquid heights are predicted using the original linear theory, a modified linear theory and computational fluid dynamics analysis. The results demonstrate that the developed method can predict sloshing motion over a wide range of excitation frequencies. However, the developed method has the limitations of linear solutions since it neglects the nonlinear features of sloshing motion. Despite these limitations, the authors believe that the developed method can be useful as a simple analytical method for predicting the sloshing motion in a rectangular pool under various external excitations.

Nonlinear sloshing in rectangular tanks under forced excitation

  • Zhao, Dongya;Hu, Zhiqiang;Chen, Gang;Lim, Serena;Wang, Shuqi
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.5
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    • pp.545-565
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    • 2018
  • A numerical code is developed based on potential flow theory to investigate nonlinear sloshing in rectangular Liquefied Natural Gas (LNG) tanks under forced excitation. Using this code, internal free-surface elevation and sloshing loads on liquid tanks can be obtained both in time domain and frequency domain. In the mathematical model, acceleration potential is solved in the calculation of pressure on tanks and the artificial damping model is adopted to account for energy dissipation during sloshing. The Boundary Element Method (BEM) is used to solve boundary value problems of both velocity potential and acceleration potential. Numerical calculation results are compared with published results to determine the efficiency and accuracy of the numerical code. Sloshing properties in partially filled rectangular and membrane tank under translational and rotational excitations are investigated. It is found that sloshing under horizontal and rotational excitations share similar properties. The first resonant mode and excitation frequency are the dominant response frequencies. Resonant sloshing will be excited when vertical excitation lies in the instability region. For liquid tank under rotational excitation, sloshing responses including amplitude and phase are sensitive to the location of the center of rotation. Moreover, experimental tests were conducted to analyze viscous effects on sloshing and to validate the feasibility of artificial damping models. The results show that the artificial damping model with modifying wall boundary conditions has better applicability in simulating sloshing under different fill levels and excitations.

Study for Effects of Sloshing Effect Reduction Device on Vessel Motion

  • Kim, Kyung Sung;Kim, Moo Hyun
    • Journal of Advanced Research in Ocean Engineering
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    • v.3 no.3
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    • pp.149-157
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    • 2017
  • Since sloshing effects influences ship motions including floater's natural frequencies. The significant factors changing ship motions are inner liquid impact loads and inertia forces and moments with respect to its filling ratio. This means that changing sloshing loads with sloshing effects reduction device (SERD) may control ship motions. In this regard, conceptual model for adjustable SERD was suggested by authors and then implanted into fully coupled program between vessel motion and sloshing. By changing clearances of baffles in the inner tank which were component of SERD, then the roll RAOs from each case were obtained. It is revealed that using well-controlled SERD can maintain natural frequencies of floater even inner tank has different filling ratio.

Sloshing Analysis of a Simple Tank using Fluid-structure Interface Method (유체-구조 연성 방법에 의한 단순 탱크 슬로싱 해석)

  • Kang, Sung-Jong;Seo, Hong-Jae;Kim, Byung-Joo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.4
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    • pp.31-37
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    • 2011
  • Fuel tank sloshing noise of vehicle is caused by flow impact on the tank wall during sudden braking, and the sloshing vibration of tank wall is a coupled phenomenon of the fuel inside tank and tank wall structure. Therefore, Fluid-Structure Interface(FSI) analysis technology should be adopted to predict accurately the sloshing vibration. In this study, FSI approach was employed to analyze sloshing phenomenon for a simple tank model with velocity change of the actual vehicle test. First, the simulated results for rigid tank model were compared with those for deformable tank model. Next, influence of baffle location and shape of baffle holes on the acceleration magnitude and the maximum stress of tank wall was investigated. In addition, sloshing analysis for tank with another baffle type was carried out.

A numerical study on sloshing impact loads in prismatic tanks under forced horizontal motion

  • Parthasarathty, Nanjundan;Kim, Hyunjong;Choi, Yoon-Hwan;Lee, Yeon-Won
    • Journal of Advanced Marine Engineering and Technology
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    • v.41 no.2
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    • pp.150-155
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    • 2017
  • Many engineering issues are caused because of sloshing phenomena. Numerical solution methods including the computational fluid dynamics (CFD) technique, are used to analyze these sloshing problems. In this study, a numerical technique was used to analyze sloshing impact loads in a prismatic tank under forced horizontal motion. The volume-of-fraction (VOF) method was adopted to model the sloshing flow. Six cases were used to compare the effects of the natural frequencies of a simple rectangular and prismatic tank, with impact pressure on the prismatic tank wall. This study also investigated the variable pressure loads and sloshing phenomena in prismatic tanks when the frequencies were changed. The results showed that the average of the peak pressure value for ${\omega}^{\prime}1=4.24=4.24$ was 22% higher than that of ${\omega}_1=4.6$.

A Sloshing Analysis of Storage Tank using Multi-layer Perceptron Artificial Neural Network (다층퍼셉트론 인공신경망을 이용한 저장탱크 슬로싱해석)

  • Kim, Hyun-Soo;Lee, Young-Shin
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.491-496
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    • 2004
  • The oscillation of the fluid caused by external forces is called sloshing, which occurs in moving vehicles with contained liquid masses, such as aircraft. cars and liquid rocket and so on. This sloshing effect could be a severe problem in vehicle stability and control. So, various baffles are used in order to reduce the sloshing. The Lagrangian, Eulerian and ALE numerical method is widely used on the analysis of sloshing presently. But, these numerical methods are needed so many CPU time. In this study, for the reduction of the sloshing analysis time, me multi.layer perceptron artificial neural network is introduced and analysis results are presented.

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Free Surface Tracking for the Accurate Time Response Analysis of Nonlinear Liquid Sloshing

  • Cho Jin-Rae;Lee Hong-Woo
    • Journal of Mechanical Science and Technology
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    • v.19 no.7
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    • pp.1517-1525
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    • 2005
  • Liquid sloshing displays the highly nonlinear free surface fluctuation when either the external excitation is of large amplitude or its frequency approaches natural sloshing frequencies. Naturally, the accurate tracking of time-varying free surface configuration becomes a key task for the reliable prediction of the sloshing time-history response. However, the numerical instability and dissipation may occur in the nonlinear sloshing analysis, particularly in the long-time beating simulation, when two simulation parameters, the relative time-increment parameter a and the fluid mesh pattern, are not elaborately chosen. This paper intends to examine the effects of these two parameters on the potential-based nonlinear finite element method introduced for the large amplitude sloshing flow.

Sloshing design load prediction of a membrane type LNG cargo containment system with two-row tank arrangement in offshore applications

  • Ryu, Min Cheol;Jung, Jun Hyung;Kim, Yong Soo;Kim, Yooil
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.8 no.6
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    • pp.537-553
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    • 2016
  • This paper addresses the safety of two-row tank design by performing the extensive sloshing model tests. Owing to the uncertainties entangled with the scale law transforming the measured impact pressure up to the full scale one, so called comparative approach was taken to derive the design sloshing load. The target design vessel was chosen as 230 K LNG-FPSO with tow-row tank arrangement and the reference vessel as 138 K conventional LNG carrier, which has past track record without any significant failure due to sloshing loads. Starting with the site-specific metocean data, ship motion analysis was carried out with 3D diffraction-radiation program, then the obtained ship motion data was used as 6DOF tank excitation for subsequent sloshing model test and analysis. The statistical analysis was carried out with obtained peak data and the long-term sloshing load was determined out of it. It was concluded that the normalized sloshing impact pressure on 230 K LNG-FPSO with two-row tank arrangement is higher than that of convectional LNG carrier, hence requires the use of reinforced cargo containment system for the sake of failure-free operation without filling limitation.

Numerical Study on Effects of Velocity Profile of Liquid Container on Sloshing (액체 용기의 속도 프로파일이 슬로싱에 미치는 영향 해석)

  • Kim, Dongjoo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.5
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    • pp.313-319
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    • 2016
  • It is very important to understand and control the sloshing in a liquid container that is partially filled with liquid. Previous studies focused primarily on the sloshing and resonance caused by sinusoidal excitations, while the present study focuses on understanding and suppressing sloshing in a container that moves rapidly from a given point to another in industrial applications. To achieve this, we first numerically predict the two-phase flow induced by the horizontal movement of a rectangular container. Then we analyze the effects of container-velocity profile (in particular acceleration/deceleration duration) on sloshing. Results show that sloshing is significantly suppressed when the acceleration/deceleration duration is a multiple of the 1st-mode natural period of sloshing.

CFD simulation of compressible two-phase sloshing flow in a LNG tank

  • Chen, Hamn-Ching
    • Ocean Systems Engineering
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    • v.1 no.1
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    • pp.31-57
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    • 2011
  • Impact pressure due to sloshing is of great concern for the ship owners, designers and builders of the LNG carriers regarding the safety of LNG containment system and hull structure. Sloshing of LNG in partially filled tank has been an active area of research with numerous experimental and numerical investigations over the past decade. In order to accurately predict the sloshing impact load, a new numerical method was developed for accurate resolution of violent sloshing flow inside a three-dimensional LNG tank including wave breaking, jet formation, gas entrapping and liquid-gas interaction. The sloshing flow inside a membrane-type LNG tank is simulated numerically using the Finite-Analytic Navier-Stokes (FANS) method. The governing equations for two-phase air and water flows are formulated in curvilinear coordinate system and discretized using the finite-analytic method on a non-staggered grid. Simulations were performed for LNG tank in transverse and longitudinal motions including horizontal, vertical, and rotational motions. The predicted impact pressures were compared with the corresponding experimental data. The validation results clearly illustrate the capability of the present two-phase FANS method for accurate prediction of impact pressure in sloshing LNG tank including violent free surface motion, three-dimensional instability and air trapping effects.