• Journal of Environmental Science International
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• v.11 no.1
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• pp.25-32
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• 2002

In order to control of water quality in Jeju harbor, variation of physical oceanographic environments was estimated using material cycle model. It is composed of the three-dimensional hydrodynamic model for the simulation at water flow and material cycle model for the simulation of water quality. The three dimensional hydrodynamic model simulation of the circulation and mixing in Jeju Harbor has been conducted forced by Sanzi River Discharge, Tidal elevation, wind and Solar heat in case of August and November, 2000 and February and May, 2001, respectively. The results of numerical model and observation show that the model can produce realistic results of current in the harbor. The monthly variation of velocity pattern are not so much changed are found In Jeju Harbor. The residual current was forced by temperature, salinity, density, wind and tidal current. The residual current of August, 2000 are the strongest among four month. It can be explained that the density effect can be important role in residual current at Jeju Harbor. As the results of salinity distribution simulation, very low concentration of all levels were simulated in August, 2000. The flowrate of Sanzi river was investigated 77,760 ㎥ /d in August, 2000. Therefore, pollutant loadings from Sanzi river should be considered for water quality management in Jeiu harbor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.63-68
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• 2017

Friction occurs when surfaces that are in contact move relatively between solid surfaces, fluid layers, and materials slide against one another. This friction force causes wear on the contact surface, generates unwanted heat and leads to performance degradation. Thus, much research has been performed to avoid friction reduction. Among these studies, a textured surface that has micro patterns on the surface has drawn attention for its ability to reduce friction. A mathematical model is developed in this study to examine friction reduction due to the texture of a surface. Numerical simulations are carried out with respect to various factors such as the shape aspect ratio and texture depth of a diamond-shaped texture in the hydrodynamic lubrication regime. As a result, a shape aspect ratio of 1 is best for friction reduction.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.111-118
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• 2014

In drilling process of oil wells, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. In this paper, a commercial CFD package(ANSYS Fluent 15.0) was used to solve the hydrodynamic force and evaluate mud mixing time in the mud mixing tank on offshore drilling platforms. Prediction of power consumption in co-rotating and counter-rotating models has been compared with results of Nagata's correlation equation. This research shows the hydrodynamic effect inside the two phase mud mixing tank according to rotating directions(co-rotating and counter-rotating). These results, we can conclude that the co-rotating direction of the two shafts with mixing blade in the mud mixing tank can be a preferable in power consumption and mixing time reduction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2106-2113
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• 1997

This paper presents the characteristics of lateral vibrations of rotor system supported by hydrodynamic journal bearings. Finite element model is developed for the dynamic analysis of rotor system. Hydrodynamic bearings are modeled with the distributed springs and dampers in shape of the 2nd order polynomials in the direction of bearing width. Experiments are conducted to measure the natural frequency, and experimental results are compared with the theoretical results that are calculated using the point model and distributed model. Theoretical results using the distributed model agrees better with the measured results as bearing width increases. Also, this method is applied to actual three-stage turbo blower model. Then, critical speed and forced vibration analysis are performed.

• Computers and Concrete
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• v.16 no.3
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• pp.429-448
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• 2015

The dams are huge structures storing a large amount of water and failures of them cause especially irreparable loss of lives during the earthquakes. They are named as a group of structures subjected to fluid-structure interaction. So, the response of the fluid and its hydrodynamic pressures on the dam should be reflected more accurately in the structural analyses to determine the real behavior as soon as possible. Different mathematical and analytical modelling approaches can be used to calculate the water hydrodynamic pressure effect on the dam body. In this paper, it is aimed to determine the dynamic response of concrete gravity dams using different water modelling approaches such as Westergaard, Lagrange and Euler. For this purpose, Sariyar concrete gravity dam located on the Sakarya River, which is 120km to the northeast of Ankara, is selected as a case study. Firstly, the main principals and basic formulation of all approaches are given. After, the finite element models of the dam are constituted considering dam-reservoir-foundation interaction using ANSYS software. To determine the structural response of the dam, the linear transient analyses are performed using 1992 Erzincan earthquake ground motion record. In the analyses, element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motions. Rayleigh damping is considered. At the end of the analyses, dynamic characteristics, maximum displacements, maximum-minimum principal stresses and maximum-minimum principal strains are attained and compared with each other for Westergaard, Lagrange and Euler approaches.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1163-1168
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• 2019

Hydrodynamic properties have been investigated for promising extraction systems: $0.05mol\;L^{-1}$ solutions of di(N-ethyl-4-ethylanilide) of 2,2'-bipyridine-6,6'-dicarboxylic acid, di(N-ethyl-4-fluoroanilide) of 2,6-pyridinedicarboxylic acid and di(N-ethyl-4-hexylanilide) of 2,2'-bipyridine-6,6'-dicarboxylic acid in meta-nitrobenzotrifluoride (F-3) or trifluoromethylphenyl sulfone (FS-13) diluents. To evaluate the perspectives for their use as extraction mixtures at the final stage of the nuclear fuel cycle, the change in density, viscosity, surface tension, and phase separation rate under irradiation with accelerated electrons was studied. The concentrations of extractants in the irradiated mixtures have been determined and the radiation-chemical yields have been calculated. Irradiation significantly decreases the phase separation rate at the stages of extraction and back extraction for all the studied systems. The viscosity of the DYP-7 solution in FS-13 increase above the values suitable for its use in extraction processes.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.29-35
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• 2011

In order to effectively control waves in a coastal zone, Multi-Cylinder Piles have been suggested as economic structures. A numerical analysis was conducted using the Delft-3D: WAVE module based on SWAN, which considered wave shoaling and refraction. Moreover, irregular waves were used to investigate the hydrodynamic characteristics of the wave interaction with the structure. In this paper, a numerical analysis was carried out to research the effect of wave control through a wave height analysis concerning an existing, concrete wave breaker and multi-cylinder piles placed at the same location. As a result, the effect of the wave control is shown using the wave breaker, multi-cylinder piles, and existing data.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.18-22
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• 2006

Hydrodynamic performance test was conducted for a fuel pump of a liquid rocket engine turbopump. The pump driven by an electric motor was tested using water. It is experimentally shown that the inducer had very small effect on the pump's head and efficiency but great effect on the pump's cavitation performance. Additionally, inducer test was carried out to investigate the effect of the inducer on the pump in detail, and it was found that the pump reached a critical cavitation number when the inducer head dropped by 55%.

• Bulletin of the Society of Naval Architects of Korea
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• v.20 no.1
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• pp.47-58
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• 1983

A study is made, in the framework of linear potential theory, to investigate the hydrodynamic characteristics of two-dimensional wave-energy absorbers as like the Salter's duck and an oscillating cam with Lewis-form section, which undergo uncoupled heaving and rolling motions in an incident linear gravity wave in deep water. Wave energy is supposed to be extracted by a linearly damped generator with an spring. Some well-known formulae in ship hydrodynamics such as Haskind-Newman relation and Bessho-Newman relation are utilized in forms of Kochin functions to derived expressions for efficiency, breaking effect and drift force of the absorber. Maximum ideal efficiency of 100% can be arrived at an prescribed tuning frequency. Coupling effect is also examined to assess the detrimental effect of sway on efficiency. From numerical calculations for both types of two-dimensional devices it may be concluded that a wave-energy absorber functions at the same time as a wave breaker and that the drift force acting on the device becomes smaller when it absorbs wave energy than as it oscillates freely. Finally the study is extended to an infinite array system, equivalent to a body in a canal, to show that all incident wave energy can be absorbed regardless of the absorber's size, only if the optimum space and the optimum condition of control are realized.

• Journal of Biomedical Engineering Research
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• v.19 no.3
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• pp.297-303
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• 1998

The sinus distal to the prosthetic heart valve influences the valve closure behavior and velocity field near the valve, therefore affects the hydrodynamic performance of the prosthetic heart valve. In order to study the effects of valve distal geometry on the hydrodynamic performance of the prosthetic valves, mechanical bileaflet valve(SJMV), monoleaflet polymer valve(MLPV) and trileaflet polymer valve(FTPV) are inserted in the test sections which have the straight and the sinus shape distal to the valve. Leakage volumes and systolic mean pressure drops are measured in the pulsatile mock circulation flow loop. Leakage volumes are slightly less and systolic mean pressure drops are higher in the sinus test section comparing to those in the straight test section, but the differences are statistically insignificant. Flow waveforms are analyzed in order to predict the valve closure behavior. The distal sinus does not affect the closure of the MLPV, but early valve closure of SJMV is observed in the sinus test section. This effect is more significant in FTPV, and the reverse flow peak of FTPV is reduced in the sinus test section. Therefore the sinus distal to the valve can reduce the reverse flow jet caused by sudden valve closure.