• Title, Summary, Keyword: Vertical mixing process

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Method for estimating workability of self-compacting concrete using mixing process images

  • Li, Shuyang;An, Xuehui
    • Computers and Concrete
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    • v.13 no.6
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    • pp.781-798
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    • 2014
  • Estimating the workability of self-compacting concrete (SCC) is very important both in laboratories and on construction site. A method using visual information during the mixing process was proposed in this paper to estimate the workability of SCC. First, fourteen specimens of concrete were produced by a single-shaft mixer. A digital camera was used to record all the mixing processes. Second, employing the digital image processing, the visual information from mixing process images was extracted. The concrete pushed by the rotating blades forms two boundaries in the images. The shape of the upper boundary and the vertical distance between the upper and lower boundaries were used as two visual features. Thirdly, slump flow test and V-funnel test were carried out to estimate the workability of each SCC. Finally, the vertical distance between the upper and lower boundaries andthe shape of the upper boundary were used as indicators to estimate the workability of SCC. The vertical distance between the upper and lower boundaries was related to the slump flow, the shape of the upper boundary was related to the V-funnel flow time. Based on these relationships, the workability of SCC could be estimated using the mixing process images. This estimating method was verified by three more experiments. The experimental results indicate that the proposed method could be used to automatically estimate SCC workability.

The differences in the potential energy anomaly for analyzing mixing and stratification between 2D and 3D model

  • Minh, Nguyen Ngoc;Hwang, Jin Hwan
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.240-240
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    • 2015
  • As Simpson et al. (1990) emphasized the importance of the straining process in the stratification and mixing in the estuarine circulation process, various researches have investigated on the relative contribution of each process to the overall potential energy anomaly dynamics. However, many numerical works have done only for two dimensional modeling along channel or the short distance cross sectional three dimensional simulations as Burchard et al. (2008) and the estuarine channel was not simulated so far. But, in the study on the physics of shallow coastal seas, spatial dimension in the three dimensional way affects significantly on results of a particular numerical model. Therefore, the comparison of two and three dimensional models is important to understand the real physics of mixing and stratification in an estuary. Also, as Geyer and MacCready (2013) pointed out that the lateral process seems to be important in determining the periodic stratifications, to study such process the three dimensional modeling must be required. The present study uses a numerical model to show the signification roles of each term of the time-dependent dynamic equation for the potential energy anomaly (PEA) in controlling along and lateral channel flows and different stratification structures. Moreover, we present the relationships between the ${\Phi}$-advection, the depth mean straining, vertical mixing and vertical advection can explain well how water level, salinity distribution and across velocity 2D model are slightly different from 3D.

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Analysis of the Ozone Transport and Seasonal Variability in the Tropical Tropopause Layer using MERRA-2 Reanalysis Data (MERRA-2 재분석자료를 활용한 적도 대류권계면층의 오존 수송 및 계절변동성 분석)

  • Ryu, Hosun;Kim, Joowan
    • Atmosphere
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    • v.30 no.1
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    • pp.91-102
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    • 2020
  • MERRA-2 ozone and atmospheric data are utilized to test the usefulness of reanalysis-based tracer transport analysis for ozone in the tropical tropopause layer (TTL). Transport and mixing processes related to the seasonal variation of TTL ozone are examined using the tracer transport equation based on the transformed Eulerian mean, and the results are compared to previously proposed values from model analyses. The analysis shows that the seasonal variability of TTL ozone is mainly determined by two processes: vertical mean transport and horizontal eddy mixing of ozone, with different contributions in the Northern and Southern Hemispheres. The horizontal eddy mixing process explains the major portion of the seasonal cycle in the northern TTL, while the vertical mean transport dominates in the southern TTL. The Asian summer monsoon likely contributes to this observed difference. The ozone variability and related processes in MERRA-2 reanalysis show qualitatively similar features with satellite- and model-based analyses, and it provides advantages of fine-scale analyses. However, it still shows significant quantitative biases in ozone budget analysis.

Micro-meteorological Characteristics during the Steam Fog over the Gumi Reservoir of Nakdong River (낙동강 구미 보의 증기 안개 발생 시의 미기상학적 특성)

  • Kim, Hae-Dong;Cho, Chang-Bum;Seo, Kwang-Su
    • Journal of Environmental Science International
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    • v.25 no.3
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    • pp.405-415
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    • 2016
  • We analyzed the micro-meteorological characteristics during typical steam fog over the Gumi Reservoir of Nakdong river with the field observation data for recent 2 year(1 April 2013~31 March 2015) collected by the national institute of meteorological research, KMA. Steam fog occur when the cold drainage flows over the warm water surface. As the sensible and latent heat from water are provided to the air, the instability of lower atmosphere is increased. The resultant vertical mixing of warm, moist air near water surface and cold air aloft causes the formation of status cloud. The convection strengthened by radiative cooling of the upper part of the stratus causes the fog to propagate downward. Also, the temperature at the lowest atmosphere is increased rapidly and the inversion near surface disappear by these processes when the fog forms. The increase of wind speed is observed because the downward transportation of momentum is caused by vertical mixing.

Diffusion of a Steady Horizontal Line Source in a Turbulent Shear Flow (난류전단(亂流剪斷) 흐름에서의 정상(定常) 수평(水平) 선오염원(線汚染源)의 확산(擴散))

  • Jun, Kyung Soo;Lee, Kil Seong
    • Journal of The Korean Society of Civil Engineers
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    • v.13 no.2
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    • pp.191-199
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    • 1993
  • Diffusion of a steady horizontal line source in a turbulent shear flow is simulated by numerically solving a steady two-dimensional advective diffusion equation. The computational result is compared with the analytic solution for uniform velocity and diffusivity distributions over the depth. The analytic solution for constant velocity and diffusivity overestimates the degree of vertical mixing. The normalized equation indicates that friction factor is the only physical parameter that governs the vertical diffusion process. Sensitivities of the diffusion process to the friction factor and initial source position are analyzed. The rate of vertical mixing varies approximately as the square root of the friction factor. The optimal source position, which gives the most rapid mixing, lies above the mid-depth and moves toward the water surface as the friction factor increases.

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Time-split Mixing Model for Analysis of 2D Advection-Dispersion in Open Channels (개수로에서 2차원 이송-분산 해석을 위한 시간분리 혼합 모형)

  • Jung, Youngjai;Seo, Il Won
    • Journal of The Korean Society of Civil Engineers
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    • v.33 no.2
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    • pp.495-506
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    • 2013
  • This study developed the Time-split Mixing Model (TMM) which can represent the pollutant mixing process on a three-dimensional open channel through constructing the conceptual model based on Taylor's assumption (1954) that the shear flow dispersion is the result of combination of shear advection and diffusion by turbulence. The developed model splits the 2-D mixing process into longitudinal mixing and transverse mixing, and it represents the 2-D advection-dispersion by the repetitive calculation of concentration separation by the vertical non-uniformity of flow velocity and then vertical mixing by turbulent diffusion sequentially. The simulation results indicated that the proposed model explains the effect of concentration overlapping by boundary walls, and the simulated concentration was in good agreement with the analytical solution of the 2-D advection-dispersion equation in Taylor period (Chatwin, 1970). The proposed model could explain the correlation between hydraulic factors and the dispersion coefficient to provide the physical insight about the dispersion behavior. The longitudinal dispersion coefficient calculated by the TMM varied with the mixing time unlike the constant value suggested by Elder (1959), whereas the transverse dispersion coefficient was similar with the coefficient evaluated by experiments of Sayre and Chang (1968), Fischer et al. (1979).

A Study on on Failure Analysis of Table Liner for Roller Mill (롤러 분쇄기용 테이블 라이너의 파손 해석에 관한 연구)

  • Lee, Dong-Woo;Hong, Soon-Hyeok;Lee, Kyoung-Young;Cho, Seok-Swoo;Joo, Won-Sik
    • Proceedings of the KSME Conference
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    • pp.163-169
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    • 2003
  • The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers load and the centrifugal force by rotation of table. It demands $4{\times}10^7$ cycle but has $4{\times}10^6{\sim}8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to 30% of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner for vertical roller mill using HDM and fatigue analysis

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A Study on Optimal Design for Vertical Roller Mill using DOE and Neural Network (실험계획법과 신경망을 이용한 수직형 롤러 분쇄기의 최적설계에 관한 연구)

  • Lee, Dong-Woo;Lee, Soo-Jin;Hong, Soon-Hyeok;Cho, Seok-Swoo;Joo, Won-Sik
    • Proceedings of the KSME Conference
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    • pp.1130-1135
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    • 2004
  • The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Vertical roller mill is subjected to the cyclic bending stress by rollers load. It demands $4{\times}10^7$ cycle but has $4{\times}10^6{\sim}8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to 30% of total maintenance. Therefore, this study shows optimal design for vertical roller mill using DOE and neural network.

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A Study on the Prediction of Failure Stress for Table Liner under Fatigue Load (피로하중을 받는 테이블 라이너의 파손응력예측에 관한 연구)

  • 이동우;주원식
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.8
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    • pp.97-105
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    • 2004
  • The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers and the centrifugal force by rotation of table. It demands $4{\times}10^7$ expense of life but has $4{\times}10^6~-8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller The repair expense fur it amounts to 30% of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner of vertical roller mill using HDM and fatigue analysis

The Mixing of Forced Plume In the Coastal Waters (연안해역 중력 분류의 혼합 과정)

  • Jang, Seon-Deok;Seo, Jeong-Mun;Lee, Jong-Seop
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.26 no.1
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    • pp.26-33
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    • 1990
  • The behavior and mixing process of the forced plume are studied in the hydraulic laboratory. The dilution rate of discharged waste water from the port in various hydraulic condition was analized. The effect of densimetric Froude number and the discharge type on the dilution rate are discussed: In the vertical discharge, the forced plume of small densimetric Froude number mixes more actively than that of the large one. In the horizontal discharge, forced plume of large densimetric Froude number dilutes more rapidly than that of the small one. The mixing takes place more vigorously in the horizontal discharge than in the vertical one. The multi-port diffuser is more effective for the waste water discharge system than the single port diffuser in the tidal swinging coastal sea.

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