• Title/Summary/Keyword: Void Distribution

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Prediction of the Volumetric Water Content Using the Soil-Water Characteristic Curve on an Unsaturated Soil (흙-수분 특성곡선 방정식을 이용한 체적함수비의 예측)

  • Song, Chang-Seob
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.7 no.6
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    • pp.39-48
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    • 2004
  • The purpose of this paper was to confirm the application of the equation of the soil-water characteristic curve on an unsaturated soil. To this ends, a series of suction test was conducted on the selected 4 kinds of soil which is located in Korea, using the modified pressure extractor apparatus. And it was carried out to analyze the experimental parameters which can describe the soil-water characteristics, were determined by using the data obtained from the experiment. From the results, it was found that the matric suction was varied according to the grain size distribution, amount of fine grain particle and void ratio. Also it was found that the residual volumetric water content was decreased with the void ratio, but the index related air entry value, the soil parameter related water content and the parameter with residual water content were increased with the void ratio. And the application of equation of the soil-water characteristic curve was confirmed for the various conditions and the various state by the comparison between the volumetric water content measured by the experiment and the predicted values.

The study on the Two-Phase Swirl Flow Characteristics in Cylindrical Pipe (원관내의 이상선회유동 특성에 관한 연구)

  • 차경옥;김재근
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.1
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    • pp.187-197
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    • 1996
  • Many investigations have been made to determine the pressure drop and heat transfer characteristics for single phase flow in tape generated swirl flow. But few studies have been carried out to investigate the heat transfer in two component, two phase swirl flow with non-boiling. An experimental study has been conducted to determine the effects of tape twist ratios on two phase convective heat transfer coefficients, pressure drop, and void fraction distribution in a non-boiling, air-water, two phase flow. The flow conditions were both swirl and non swirl flows. The internal diameter of the test section is 42.5mm. The tape twist ratios of pitch to diameter ratio varied from 4.0 to 10.6. The heating conditions were isothermal and nonisothermal. The flow patterns identified with experiments were bubbly, bubbly-slug, slug, and slug-annular flow in up-flow. This study has concluded that no significant difference in void fraction distribution were observed both isothermal and nonisothermal conditions, the pressure drop for two phase flow with twisted tape swirler increase as the tape twist ratio decrease, and that values of two phase heat transfer coefficient increase when the tape twist ratio decreases.

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Investigation on effect of neutron irradiation on welding residual stresses in core shroud of pressurized water reactor

  • Jong-Sung Kim;Young-Chan Kim;Wan Yoo
    • Nuclear Engineering and Technology
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    • v.55 no.1
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    • pp.80-99
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    • 2023
  • This paper presents the results of investigating the change in welding residual stresses of the core shroud, which is one of subcomponents in reactor vessel internals, performing finite element analysis. First, the welding residual stresses of the core shroud were calculated by applying the heat conduction based lumped pass technique and finite element elastic-plastic stress analysis. Second, the temperature distribution of the core shroud during the normal operation was calculated by performing finite element temperature analysis considering gamma heating. Third, through the finite element viscoelastic-plastic stress analysis using the calculated temperature distribution and setting the calculated residual stresses as the initial stress state, the variation of the welding residual stresses was derived according to repeating the normal operation. In the viscoelastic-plastic stress analysis, the effects of neutron irradiation on mechanical properties during the cyclic normal operations were considered by using the previously developed user subroutines for the irradiation agings such as irradiation hardening/embrittlement, irradiation-induced creep, and void swelling. Finally, the effect of neutron irradiation on the welding residual stresses was analysed for each irradiation aging. As a result, it is found that as the normal operation is repeated, the welding residual stresses decrease and show insignificant magnitudes after the 10th refueling cycle. In addition, the irradiation-induced creep/void swelling has significant mitigation effect on the residual stresses whereas the irradiation hardening/embrittlement has no effect on those.

Image analysis of an air void system in hardened concrete (경화콘크리트 내부의 기포분포상태 분석에 관한 연구)

  • 김기철;정재동
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.10b
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    • pp.791-796
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    • 1998
  • Air voids existed in hardened concrete have an important influence on concrete deterioration such as carbonation, freezing and thawing, and corrosion of embedded steel in concrete. Therefore it is very significant to investigate the pore structure of system(size, number and continuity of air voids) to solve the reason caused concrete deterioration. The purpose of this study is to develop the standard method of measuring air voids which affect properties in hardened concrete using image analyzing system. This paper presents the settlement of rapid and exact experimental method which extracts fine bubbles, calculates the number of air voids, and determines air-void distribution using image analyzing system with computer.

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A study on the A.C. breakdown characteristics of cross-linked polyethylene dielectrics subjected to the impulse fatigue (충격피로를 받은 가교폴리에틸렌 유전체의 교류절연파괴 특성에 관한 연구)

  • 곽영순;손제봉
    • 전기의세계
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    • v.29 no.9
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    • pp.577-583
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    • 1980
  • This paper is intended to analyze the characteristics of breakdown of polyethylene dielectrics, which was caused by A.C. voltage after impulse fatigue, by using weibull distribution. The impact of impulse fatigue upon the accurance and development of tree and the impact of void upon treeing are investigated. From the results of experiment, it is found that the life of polyethylene subjected to impulse voltage is shorter than that not subjected to impulse voltage. And in the case of void existence, it's life comes to be short remarkably, and the breakdown is almost concentrated on its initiation. From the results observed by the microscope, it is found that the treeing phenomena varies according as whether impulse voltage was applied to polyethylene before being applied to A.C. voltage and whether polyethylene has void or not.

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Prediction of Consolidational Settlement of Dredged and Reclaimed Ground (준설매립토지반의 압밀침하량 예측)

  • Yoo, Nam-Jae;Park, Byung-Soo;Jeong, Gil-Soo
    • Journal of Industrial Technology
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    • v.21 no.A
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    • pp.317-327
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    • 2001
  • For soils with high void ratios, the inverse method of utilizing results obtained from centrifuge model test was used to find the constitutive relation of effective stress - void ratio - permeability whereas conventional oedometer test and constant rate of strain consolidation test were also used to fine its relation at ranges of relatively low void ratio. Results of column test about settlement of interface and pore pressure and distribution with time were compared with numerically estimated values to confirm such a constitutive relation as obtained from the inverse method. Consolidational settlement in dredged and reclaimed ground, where the consolidation was in progress, was predicted by using the numerical technique implemented with the finite strain consolidation theory.

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An Experimental Study on the Strength Development of Porus Concerte according to the Mixing Ratio of Aggregate. (골재의 혼합비율에 따른 포러스콘크리트의 강도 증진을 위한 실험적 연구)

  • 김재환;유범재;백용관;김규용;박정호;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.253-256
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    • 2000
  • The functions of porous concrete were influenced by continuous void, and it differ greatly from the distribution and size shape of continuous void in the same void volume. And porous concrete has been few used because the strength level of porous concrete is lower than that of ordinary concrete at the present time. So the purpose of this study is to increase the strength of porous concrete at the range of satisfying its function, analyze those effects of the mixing ratio of aggregate, affecting the development of its strength.

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A Study on the Real Quality and Void Fraction of Subcooled Refrigerant Flow (과냉 비등류의 실제건도와 보이드율에 관한 연구)

  • Kim, J.H.;Kim, C.S.;Kim, K.K.;Oh, C.
    • Journal of Advanced Marine Engineering and Technology
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    • v.17 no.2
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    • pp.36-43
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    • 1993
  • Real quality and axial void fraction distribution of subcooled refrigerant flow is very important to predict the heat transfer rate and pressure drop in the design of refrigerating system. In the subcooled boiling region, the liquid bulk temperature is still below the corresponding saturation temperature. But beyond the net vapor generation point, bubble detachment is occured actively from the vapor layer formed on the wall. A reliable method to predict the vapor fraction from the liquid bulk temperature is suggested in this paper. And also the actual quality of the subcooled R-113 flow is calculated in the range of 261-1239kg/$m^2$s mass velocity and 10-30K subcooling.

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INVESTIGATION OF DRAG REDUCTION MECHANISM BY MICROBUBBLE INJECTION WITHIN A CHANNEL BOUNDARY LAYER USING PARTICLE TRACKING VELOCIMETRY

  • Hassan Yassin A.;Gutierrez-Torres C.C.
    • Nuclear Engineering and Technology
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    • v.38 no.8
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    • pp.763-778
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    • 2006
  • Injection of microbubbles within the turbulent boundary layer has been investigated for several years as a method to achieve drag reduction. However, the physical mechanism of this phenomenon is not yet fully understood. Experiments in a channel flow for single phase (water) and two phase (water and microbubbles) flows with various void fraction values are studied for a Reynolds number of 5128 based on the half height of the channel and bulk velocity. The state-of-the art Particle Tracking Velocimetry (PTV) measurement technique is used to measure the instantaneous full-field velocity components. Comparisons between turbulent statistical quantities with various values of local void fraction are presented to elucidate the influence of the microbubbles presence within the boundary layer. A decrease in the Reynolds stress distribution and turbulence production is obtained with the increase of microbubble concentration. The results obtained indicate a decorrelation of the streamwise and normal fluctuating velocities when microbubbles are injected within the boundary layer.

A Study on the Breakdown Characteristics in Cross-linked Polyethylene by Treeing Effect (가교폴리에틸렌의 내부방전효과에 의한 절연파괴특성)

  • 곽영순;이양성;조정수
    • 전기의세계
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    • v.27 no.6
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    • pp.76-83
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    • 1978
  • This paper reveals the results of fundamental experiments with the breakdown strength- and treeing phenomena, by A.C voltage and impulse voltage, of cross-linked polyethylene insulator, respectively compared in each case of the various specimens; nonvoid, air void, water void, oil void and oil impregnated one, all articially made. In this research, the V-t and V-n characteristics are investigated by means of the Weibull distribution and are analysed the characteristics of fatigue breakdown caused by the A.C and impulse voltage. Based on numerous tests, treeing effect and treeing breakdown mechanism is investigated through microscopic photographs taken to clarify the shapes of each tree and treeing breakdown phenomena.

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