• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.265-277
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• 2003

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.89-92
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• 2006

In the present study, the flow field of a mesh type suppressor with varying holes at the central portion is studied to investigate drain flow characteristics in a cylindrical tank. Further, an attempt is made to understand the changes in the flow field brought about by the suppressors of different kinds in a circular tank which ultimately prevents vortex formation. For this purpose, flow visualization studies using PIV (Particle Image Velocimetry) to determine the flow patterns in a cylindrical tank with circular cross section without suppressor and with suppressor are carried out after imparting rotation to the liquid in the tank. Results are obtained when there is no draining and with draining. The flow field is visualized both in horizontal and vertical planes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.171-181
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• 2012

The design of high strength underground septic tank stiffened by steel pipe is presented and the ultimate behavior is investigated according to the full scale experiments for three types of specimens. The limitation of the current design specification are pointed out and the general design procedure of private sewage treatment facility are newly developed considering thickness of FRP shell, types of steel pipe stiffer and diaphragm wall. The direct tensile and bending test for FRP material of septic tank were performed. The increase effect of ultimate strength due to the circular steel pipe are investigated by the full scale field test and compared with the results by the finite element analysis.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.759-765
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• 2002

Prestressing tendons in the wall of circular storage tank are investigated from the viewpoint of equivalent load method. Special attention is paid to the effectiveness of eccentricities of the hoop and vertical tendons. Local effect at the bent Point of vertical tendon in the wall with varying thickness is examined. Some aspects which are frequently overlooked or misinterpreted in the conventional analyses of vertical tendons are discussed. Numerical examples are presented to emphasize the significance of accurate analysis of the vortical tendon in practice. It is expected that the equivalent load method can be effectively used to simplify the analysis of tendons in the circular wall and to minimize the errors.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.751-759
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• 2003

The theoretical method is developed to investigate the vibration characteristics of the sloshing and bulging mode for the circular cylindrical storage tank with an annular plate on free surface. The cylindrical tank is filled with an inviscid and incompressible liquid. The liquid domain is limited by a rigid cylindrical surface and a rigid flat bottom. As the effect of free surface waves Is taken into account in the analysis, the bulging and sloshing modes are studied. The solution for the velocity potential of liquid movement is assumed as a suitable harmonic function that satisfies Laplace equation and the relevant boundary conditions. The Rayleigh-Ritz method is used to derive the frequency equation of the cylindrical tank. The effect of Inner-to-outer radius ratio and thickness of annular plate and liquid volume on vibration characteristics of storage tank is studied. The finite element analysis is performed to demonstrate the validity of present theoretical method.

• Computational Structural Engineering
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• v.10 no.4
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• pp.291-302
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• 1997

This paper presents an analytical method for evaluating the free vibration of a circular cylindrical tank filled with bounded compressible fluid. The analytical method was developed by means of the finite Fourier series expansion method. The compressible fluid motion was determined by means of the linear velocity potential theory. To clarify the validity of the analytical method, the natural frequencies of a circular cylindrical tank with the clamped-clamped boundary condition, and filled with water, were obtained by the analytical method and the finite element method using a comercial ANSYS 5.2 software. Excellent agreement on the natural frequencies of the liquid-filled tank structure was found. The compressiblity and the fluid density effects on the normalized coupled natural frequencies were investigated. The density of fluid affects on all coupled natural frequencies of the tank, whereas the compressibility of fluid affects mainly on the natural frequencies of lower circumferential modes.

• Fisheries and Aquatic Sciences
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• v.16 no.3
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• pp.211-220
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• 2013

A shaking motion could be used to improve fish escapement from a cod-end net by creating a sieving effect over the swept volume or by disturbing the optomotor response of the fish. In this study, a perpendicular shaking motion was generated in a towed cod-end net by a circular canvas attached to the end of the codend, which formed a biased cap-like shape. This concept was tested by using a model in a flow tank and by towing a prototype cod-end during sea trials. For the model tests, the amplitude of the shaking motion was $0.6{\pm}0.1$ times the rear diameter of the cod-end, and the period of the shaking motion was $2.6{\pm}0.1$ s at a flow velocity of 0.6 or 0.8 m/s. In the sea trials, the amplitude was $0.5{\pm}0.2$ times the rear diameter of the cod-end, and the period of the shaking motion was $7{\pm}4$ s at towing speeds of 1.2 or 1.7 m/s. Thus, the shaking amplitude during the sea trials was equal to or less than that observed in the tank tests, and the shaking period was twice as long. The shaking motion described by the amplitude and period could be an effective means to stimulate fish escapement from cod-end during fishing operations considering the response of the fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.21-29
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• 1998

In order to investigate the fish behavior in the water tank, the three dimensional positioning system with two CCD cameras was designed. The positioning system was tested at the vertical circulation water channel with observational part of 1,500L$\times$1,500W$\times$500H mm and the circular water tank with 2,050ø sub(1)$\times$1,850ø sub(2)$\times$400H mm. The observational error of vertical direction was larger than that of horizontal direction, and the observational error became enlarged in all directions according to the increase of depth and distance from the visual axis. The maximum observational errors of horizontal and vertical directions at the circulation channel ranged from -1.7 cm to 1.8 cm (2.4%) and zero to 2.1 cm (4.2%), respectively. But the errors of horizontal and vertical directions at the circular tank ranged from -1.3 cm to 1.3 cm (1.3%) and zero to 1.3 cm (3.3%), respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.11
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• pp.747-752
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• 2015

Underwater radiated noise is an important characteristic in the naval weapon systems. It is difficult to measure the radiation efficiency of underwater vehicle, such as UUV(unmanned underwater vehicle) and underwater weapons in real operation environment. In this study, acoustic radiation efficiency of a circular cylindrical structure is measured in the laboratory-water tank. The radiation efficiency is compared with the numerical results and it is found that they are in a good agreement. Therefore, the measurement method can be applied effectively for predicting the underwater radiation noise and effectiveness of radiation reduction means.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.2
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• pp.166-172
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• 2007

The flow around a rotating circular cylinder near a plane wall is investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique in the circulating water tank. The experimental parameters are the rotating direction of the cylinder. the space ratios $H/D(H/D=0.05{\sim}0.5)$ between cylinder and plane wall and the velocity ratios ${\alpha}({\alpha}=0{\sim}{\pm}2.0)$. In the case of clockwise, the lift on the rotating circular cylinder was increased with the reduction of the space ratios and with the velocity ratios, the upper separation point was more shifted in the rotating direction with them. In the case of anticlockwise, the absolute value of the lift on the rotating circular cylinder was increased with increasing the space ratios and the velocity ratios. the lower separation point was more shifted in the rotating direction with them.