• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1263-1274
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• 2009

Several experimental tests to simulate a reflood phase of a cold-leg LBLOCA of the APR1400 have been performed using the ATLAS facility. This paper describes the related experimental results with respect to the thermal-hydraulic behavior in the core and the system-core interactions during the reflood phase of the cold-leg LBLOCA conditions. The present descriptions will be focused on the LB-CL-09, LB-CL-11, LB-CL-14, and LB-CL-15 tests performed using the ATLAS. The LB-CL-09 is an integral effect test with conservative boundary condition; the LB-CL-11 and -14 are integral effect tests with realistic boundary conditions, and the LB-CL-15 is a separated effect test. The objectives of these tests are to investigate the thermal-hydraulic behavior during an entire reflood phase and to provide reliable experimental data for validating the LBLOCA analysis methodology for the APR1400. The initial and boundary conditions were obtained by applying scaling ratios to the MARS simulation results for the LBLOCA scenario of the APR1400. The ECC water flow rate from the safety injection tanks and the decay heat were simulated from the start of the reflood phase. The simulated core power was controlled to be 1.2 times that of the ANS-73 decay heat curve for LB-CL-09 and 1.02 times that of the ANS-79 decay curve for LB-CL-11, -14, and -15. The simulated ECC water flow rate from the high pressure safety injection pump was 0.32 kg/s. The present experimental data showed that the cladding temperature behavior is closely related to the collapsed water level in the core and the downcomer.

• 한국농공학회논문집
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• 제56권5호
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• pp.67-75
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• 2014

In this study, the large-scale hydraulic model test was performed to investigate the hydraulic characteristics for development of the non-power soil cleaning and keeping system at the dike gate. The outlet height, outflow number, outflow discharge, and outflow cycle were compared and analyzed. The non-power soil cleaning and keeping system was most effective at 11.2 mm in the outlet height. And then the mean outflow cycle was 1.09 sec, and the mean outflow discharge was $0.00164m^3/s$. The total outflow number increased gradually as the water level of a water tank increased, and the outlet height decreased. As a level of water tank decreased, the mean outflow cycle was lengthened, and the unit outflow discharge increased. This result showed this system was most effective. To remove the silty clay deposited in facilities, the methods of excavation, dredging, high pressure washing, etc have been applied to the tidal facilities such as land reclamation, a small size fishing port, and a harbor for maintenance. However, this is extremely cost-ineffective, whereas the non-power soil cleaning and keeping system will bring about an enormously positive economic effect. In addition, when the non-power soil cleaning and keeping system is applied to the dike gate of land reclamation, a thorough examination of the local tidal data and the careful system planning are required to prevent the disaster damage caused by flooding.

• 한국농공학회지
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• 제35권2호
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• pp.43-56
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• 1993

The laboratory tests are performed on how the liquefaction potential of the sea dike structures on the saturated sand or silty sand seabed could be affected due to earthquake before and after construction results are given as follows ; 1. Earthquake damages to sea dike structures consist of lateral deformation, settlement, minor abnormality of the structures and differential settlement of embankments, etc. It is known that severe disasters due to this type of damages are not much documented. Because of its high relative cost of the preventive measures against this type of damages, the designing engineer has much freedom for the play of judgement and ingenuity in the selection of the construction methods, that is, by comparing the cost of the preventive design cost at a design stage to reconstruction cost after minor failure. 2. The factors controlling the liquefaction potential of the hydraulic fill structure are magnitude of earthquake(max. surface velocity), N-value(relative density), gradation, consistency(plastic limit), classification of soil(G & vs), ground water level, compaction method, volumetric shear stress and strain, effective confining stress, and primary consolidation. 3. The probability of liquefaction can be evaluated by the simple method based on SPT and CPT test results or the precise method based on laboratory test results. For sandy or silty sand seabed of the concerned area of this study, it is said that evaluation of liquefaction potential can be done by the one-dimensional analysis using some geotechnical parameters of soil such as Ip, Υt' gradation, N-value, OCR and classification of soils. 4. Based on above mentioned analysis, safety factor of liquefaction potential on the sea bed at the given site is Fs =0.84 when M = 5.23 or amax= 0.12g. With sea dike structures H = 42.5m and 35.5m on the same site Fs= 3.M~2.08 and Fs = 1.74~1.31 are obtained, respectively. local liquefaction can be expected at the toe of the sea dike constructed with hydraulic fill because of lack of constrained effective stress of the area.

• Journal of Welding and Joining
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• 제26권1호
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• pp.63-68
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• 2008

This paper has aimed to prevent excessive heat input by controlling arc distribution and heat input capacity with pulse GTAW in order to improve weld quality in 0.08mm pressure gauge diaphragm and flange welding parts. A design of experiment was designed using Box-Behnken method to optimize a welding process. The pulse GTAW parameters such as pulse current, base current, pulse duty, frequency and welding speed were set to input variables while hydraulic pressure that represents welding characteristics in diaphragm and flange joint were set to output variables. Based on the test result, a second regression equation was obtained between input and output variables and turned out significant. Besides, an influence of parameters has been confirmed through response surface analysis using the second-order regression equation and optimum welding condition was obtained through a grid-search method. The optimum welding condition was set to pulse current 84.4(A), base current 29.6(A), pulse duty 58.8(%), frequency 10(%), and welding speed 596(mm/min). Then, decent bead shape was acquired with no excessive heat input under the $2.3kgf/cm^2$ of hydrostatic pressure.

• International Journal of Fluid Machinery and Systems
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• 제5권4호
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• pp.152-160
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• 2012

Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rate, both with and without a surge tank placed just upstream of the inlet volute. The surge frequency at smaller flow rate was much smaller than the swirl mode frequency caused by the whirl of vortex rope. An unsteady CFD was carried out with two boundary conditions: (1) the flow rate is fixed to be constant at the volute inlet, (2) the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.

• 한국지반공학회논문집
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• 제20권1호
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• pp.75-82
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• 2004

본 연구에서는 지지대상층이 아닌 투수 대상층으로서의 풍화토 지반에 초점을 맞추어 불교란 풍화토 시료를 이용해 다양한 구속압 조건에서 동수경사를 변화 시켜가면서 연성벽체 투수시험을 수행하였다. 동수경사 및 구속압이 풍화토의 투수특성에 미치는 영향을 투수계수를 이용하여 분석하였으며, 사질토에 대해서도 유사한 시험을 수행하여 사질토와는 구별되는 풍화토만의 침투 특성을 평가하였다. 또한 풍화토 지반의 파이핑 특성을 분석하기 위하여 모형 파이핑 시험을 수행하였다. 실험결과로부터 동수경사의 범위에 따라 풍화토는 서로 다른 투수특성을 보임을 알 수 있으며, 파이핑에 대하여 사질토에 비해 매우 높은 저항 능력을 가짐을 알 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.386-391
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• 2006

This study presents experimental results of sloshing phenomenon done on rectangular box. A simple harmonic excitation was done on the box. Two kinds of filling ratio, 20% and 30% of height, were tested. A total of 15 pressure sensors were installed to monitor the impact pressure. Each test was repeated for 20 times to ensure the repeatability. The high speed camera captured the flaw filed and the corresponding pressure were synchronize with video signal so that the video image can help the interpretation of the impact pressure. The two filling ratio made difference in the flaw characteristic and impact pressure. The use of high speed camera made it possible to understand the bubble generation mechanism. The pressure time histories were presented.

• 한국지반신소재학회논문집
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• 제7권2호
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• pp.15-21
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• 2008

인공연직배수재는 일반적인 샌드드래인에 비하여 비용 절감, 지반 교란의 최소화, 시공성 및, 시공 중에 발생될 수 있는 배수재의 변형을 최소화하는 유연성을 지니고 있다. 본 연구에서는 실내실험을 통하여 측압과 동수경사에 따른 여러형태 PVD의 통수능을 도출하였다. 시험결과는 압밀된 점토에 대한 과압력이 증가하였으며, 또한 PVD 공시체의 측압도 증가하였다. 이는 측압이 증가함에 따라 통수능이 감소됨을 나타내고 있으며, PVD 코어의 공극크기는 통수능과 비례관계에 있음을 보여준다. 현장조건을 고려하여 시뮬레이션을 통한 침하량에 대한 수치해석을 수행한 결과 현장계측한 침하량과 유사하게 나타났다.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.874-881
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• 2006

Combustion stability characteristics in actual full-scale combustion chamber of a rocket engine are investigated by experimental tests with the model (sub-scale) chamber. The present hot-fire tests adopt the combustion chamber with three configurations of triplet impinging-jet injectors such as F-O-O-F, F-O-F, and O-F-O configurations. Combustion stability bound-aries are obtained and presented by the parameters of combustion-chamber pressure and mixture (oxidizer/fuel) ratio. From the experimental tests, two instability regions are observed and the pressure oscillations have the similar patterns irrespective of injector configuration. But, the O-F-O injector configuration shows broader upper-instability region than the other configurations. To verify the instability mechanism for the lower and upper instability regions, air-purge acoustic test is conducted and the photograph or the flames is taken. As a result, it is found that the pressure oscillations in the two regions can be characterized by the first impinging point of hydraulic jets and pre-blowout combustion, respectively.

• 한국철도학회논문집
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• 제8권2호
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• pp.182-187
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• 2005

Air spring system was widely accepted for railway vehicle secondary suspension to reduce and absorb the vibration and noise. The low natural frequency ensures a comfortable ride and an invariably good stiffness. In this paper, the characteristics and durability test was conducted in laboratory by using servo-hydraulic fatigue testing system to reliability evaluation of air spring for electric railway vehicle. The experimental results show that the characteristics and durability of domestically developed productions are shown in good results. And to guarantee the adaption of air spring, the ride comfort and air pressure variation were measured in train test on subway line.