• Advances in aircraft and spacecraft science
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• v.9 no.4
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• pp.349-366
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• 2022

The ability of baffles in increasing the sloshing damping is investigated in this study by theoretical, numerical, and experimental methods. Baffles Installed as separators in containers, can change the dynamic properties of sloshing. The main purpose of this study is to investigate the effect of baffle placement.The main purpose of this study is to investigate the effect of placing baffles in order to provide appropriate frequencies and damping and to present a practical baffle arrangement in the design ofsloshing. In this regard, an experimental setup is designed to study the fluid sloshing behavior and damping properties in cylindrical tanks filled up to an arbitrary depth. A new combination of annular and sectorial baffles is employed to evaluate fluid sloshing in the tank. The results show that the proposed baffle arrangement has a desired effect on the damping and fluid sloshing frequencies and optimally satisfies the anticipated design requirements. In addition, the theoretical frequencies exceed empirical frequencies at the points far from baffles, while at the points close to baffles, the empirical ones are higher than theoretical ones. Also, at the depths near the bottom of container sloshing frequencies are not affected by sectorial baffles, although the theoretical curve predicts a reduction in the fundamental frequency of sloshing. Finally, the results of finite volume and finite element methods which compared with experimental data, indicated a good agreement between different approaches.

• Advances in aircraft and spacecraft science
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• v.10 no.5
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• pp.439-455
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• 2023

Free surface fluid oscillation in prolate spheroidal tanks has been investigated analytically in this study. This paper aims is to investigate the sloshing frequencies in spheroidal prolate tanks and compare them with conventional cylindrical and spherical containers to select the best tank geometry for use in space launch vehicles in which the volume of fuel is very high. Based on this, the analytical method (Fourier series expansion) and potential fluid theory in the spheroidal coordinate system are used to extract and analyze the governing differential equations of motion. Then, according to different aspect ratios and other parameters such as filling levels, the fluid sloshing frequencies in the spheroidal prolate tank are determined and evaluated based on various parameters. The natural frequencies obtained for a particular tank are compared with other literature and show a good agreement with these results. In addition, spheroidal prolate tank frequencies have been compared with sloshing frequencies in cylindrical and spherical containers in different modes. Results show that when the prolate spheroidal tank is nearly full and in the worst case when the tank is half full and the free fluid surface is the highest, the prolate spheroidal natural frequencies are higher than of spherical and cylindrical tanks. Therefore, the use of spheroidal tanks in heavy space launch vehicles, in addition to the optimal use of placement space, significantly reduces the destructive effects of sloshing.

• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.877-895
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• 2016

This paper is concerned with the analytical derivation of natural sloshing frequencies of liquid in annular cylindrical tank and its verification by experiment. The whole liquid domain is divided into three simple sub-regions, and the region-wise linearized velocity potentials are derived by the separation of variables. Two sets of matrix equations for solving the natural sloshing frequencies are derived by enforcing the boundary conditions and the continuity conditions at the interfaces between sub-regions. In addition, the natural sloshing frequencies are measured by experiment and the numerical accuracy of the proposed analytical method is verified through the comparison between the analytical and experimental results. It is confirmed that the present analytical method provides the fundamental sloshing frequencies which are in an excellent agreement with the experiment. As well, the effects of the tank radial gap, the bottom flow gap and the liquid fill height on the fundamental sloshing frequency are parametrically investigated.

• 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.

• 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 ${\omega}_1=4.6$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.172-175
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• 2002

Sloshing of fuel in a liquid propellant tank is an important part of the dynamic and the stability analysis of the rocket. Baffles are installed in a propellant tank to reduce the instability due to sloshing. Multi degree of spring-mass-damper model was used to model sloshing of fuel in an axisymmetric tank. The natural frequencies and damping ratios are estimated. In order to verify the estimated natural frequencies and damping ratios, tests are performed for the real propellant tank of KSR-III with single ring baffle. Results of fuel sloshing analysis are compared with those of tests.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.323.2-323
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• 2002

Sloshing of fuel in a liquid propellant tank is an important part of the dynamic and the stability analysis of the rocket. Baffles are installed in a propellant tank to reduce the instability due to sloshing. Multi degree of spring-mass-damper model was used to model sloshing of fuel in an axisymmetric tank. The natural frequencies and damping ratios are estimated. In order to verify the estimated natural frequencies and damping ratios, tests are performed for the real propellant tank of KSR-III with single ring baffle. Results of fuel sloshing analysis are compared with those of tests.

• Structural Engineering and Mechanics
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• v.47 no.3
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• pp.331-343
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• 2013

The natural sloshing frequencies of annular cylindrical TLD are parametrically investigated by experiment, aiming at the exploration of its successful use for suppressing the structural vibration of spar-type floating wind turbine subject to multidirectional wind, wave and current excitations. Five prototypes of annular cylindrical TLD are defined according to the inner and outer radii of acryl container, and eight different liquid fill heights are experimented for each TLD prototype. The apparent masses near the first and second natural sloshing frequencies are parametrically investigated by measuring the apparent mass of interior liquid sloshing to the acceleration excitation. It is observed from the parametric experiments that the first natural sloshing frequency shows the remarkable change with respect to the liquid fill height for each TLD model with different container dimensions. On the other hand, the second natural sloshing frequency is not sensitive to the liquid fill height but to the gap size, for all the TLD models, convincing that the annular cylindrical sloshing damper can effectively suppress the wave- and wind-induced tilting motion of the spar-type floating wind turbine.

• 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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.8
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• pp.591-597
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• 2003

The oscillation of the fluid caused by external motions is called sloshing, which occurs in moving vehicles with contained fluid masses, such as the oil tankers, railroad cars, aircraft and rockets. Natural frequencies of fluid are much lower than that of solid structures, and the deformation caused by the excitation that is less than 1st natural frequency of fluid is very large. For the reason of that, sloshing characteristics under the ekcitation that is less than the 1st natural frequency must be studied prior to the consideration of natural frequencies of fluid. The experimental devices are constructed to simulate the translation motion. The rectangular tanks are made to study the sloshing characteristics under external excitation. The changes of water height are measured using an analogue camcorder and MPEG board, and those are compared to each other through a standard deviation. From the results of experiments, the sloshing is greatly influenced by the length of the rectangular tank than the width of that under the periodic translational motion in the length direction. The rapid amplification of sloshing by resonance is also confirmed experimentally.