• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.13-19
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• 1995

An experimental investigation has been made for flow in a circular cylinder with a rotating bottom disk. Flow system considered in this paper is a characteristic model of interior flows of an electric washing machine. Flows in a tub of an electric washing machine are driven by a rotating bottom disk called a pulsator. The simple and characteristic model was composed of a circular cylinder with impulsively rotating endwall disk and a viscous fluid in it. Rotational motion of the pulsator is periodic and alternative in rotation direction. The flow field in the interior region is governed by a horizontal boundary layer forms on the impulsively rotating disk. Experimental approach was accomplished by adopting an image processing technique for velocity measurements. Comprehensive details of the flow structure are presented. Also a meridional circulation is obtained by tracking image particles suspended in the fluid. Flow structure and data are successfully procured for this complex rotating flow field.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.36-43
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• 2000

In this paper a Vortex Lattice Method is used to predict the performances of a contra-Rotating Propeller. Greeley and Kerwin's(1982) wake model is adopted instead of the exact trailing vortex geometry. The interaction of the two propellers is treated by the sense that the induction of one propeller upon the other propeller is averaged in the circumferential direction . Two single propellers (DTRC 4119 & DTRC 4842) are chosen and compared with the experimental and other numerical results published. Then the computational results for three CRP's (4-0-4 CRP(DTRC 3686+DTRC 3687A) 4-0-5 CRP(DTRC 3686+DTRC 3849) & DTRC CRT(DTRC 5067+DTRC 5068) are compared with the experimental and numerical results published. The interaction of both propellers by the change of inflow velocity and circulation of each propeller is investigated.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.56-63
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• 1995

A simulation of contaminant dispersion in a water reservoir has been done using 2-D finite difference method(FDM). The steady state velocity field of the reservoir was computed using stream function-vorticity formulation of Wavier-Stokes equation and continuity equation. Based on the computed steady state velocity field, the transient convective diffusion equation of the contaminant dispersion was computed. For the 1m$\times$1m reservoir model with inlet and outlet attached, it was shown that the center of circulation located toward right. For the numerical values of v =0.01($\textrm{cm}^2$/s) and D=0.6($\textrm{cm}^2$/s) and the flow of 50($\textrm{cm}^3$/s ), it was determined that the outflow had to be shut down in 18 seconds to prevent from severe pollution. Also the required time was computed to be 6 seconds for the inflow of 100 ($\textrm{cm}^3$/s). The result of this study is considered, hopefully, to be useful for the design of the water reservoir systems that are the subjects to various contamination.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.791-797
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• 2012

Mineral insulating oils are an important insulating materials in oil-filled transformer. However, the mineral oil is the cause of the environmental problem. The vegetable oils are substitutes for mineral oil because of its biodegradability characteristic. As large size and high rating of the transformer increases, the losses increase at a faster rate. So insulating oil is forced circulation in the oil-filled transformer by using oil pumps. The flow electrification occurs when insulating oil was forced to be circulated. To check the flow electrification, had conducted experiments varying factors. As a result, the streaming electrification could see the changes according to flow velocity, oil temperature and insulation materials.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.219-222
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• 2001

The objective of the present study is to evaluate the effects of the stenting shapes on flow velocity and wall shear stress in angulated coronary stenosis by computer simulation. Coronary angiogram and Doppler ultrasound measurement in the patients with angulated coronary stenosis were obtained. Inlet wave velocity distribution obtained from in vivo intracoronary Doppler data was used for the numerical simulation. Spatial pattern of blood flow velocity and recirculation area were drawn through out the selected segment of coronary models. Wall shear stresses in the intracoronary stent models were calculated from three-dimensional computer simulation. A negative shear stress region, which is consistent with re-circulation area on flow pattern, was noted on the inner wall of post-stenotic area of pre-stenting model. The negative shear stress was disappeared after stenting. Shear stress in the post-stenting model was markedly reduced up to about two orders of magnitude compared to that of the pre-stenting model.

• Journal of the Korean Society of Radiology
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• v.3 no.4
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• pp.5-12
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• 2009

Arterial blood from the heart chonggyeong passed directly to the cerebral arteries and the blood circulation is important, especially in arteries that prevent blood flow there are several variables. Among the variables the average flow velocity, pulse index, and blood flow resistance and which variables, double maekbakjisuna systolic and diastolic blood flow resistance index at the maximum rate and blood pressure associated with this because they are important variables, The change of variables such as speed noehyeolryu There are observations about the non-invasive ultrasound measurements using Doppler noehyeolryu uses. Up to 20 men in the exercise of noeroganeun hyeolryuin chonggyeong arteries to increase blood flow rates can be found.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.717-720
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• 2002

The present study is to evaluate the performances of flow velocity and wall shear stress in the stenosed coronary artery using human in vivo hemodynamic Parameters and computer simulation. Initial and follow-up coronary angiographics in the patients with angulated coronary stenosis are performed. Follow-up coronary angiogram demonstrated significant difference in the percent of diameter in the stenosed coronary between two groups ($Group\;1:\;40.3{\%},\;Group\;2:\;25.5{\%}$). Flow-velocity wave obtained from in vivo intracoronary Doppler ultrasound data is used for the boundary condition for the computer simulation. Spatial and temporal variations of flow velocity vector and recirculation area are drawn throughout the selected segment of coronary models. The WSS of pre- and post-intracoronary stenting are calculated from three-dimensional computer simulation. Then negative shear stresses area on 3D simulation we noted on the inner wall of the post-stenotic area before stenting. The negative WSS is disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2. The present study suggest that hemodynamic forces exerted by pulsatile coronary circulation termed WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. The local recirculation area which has low or negative WSS, might lead to progression of atherosclerosis.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.759-764
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• 2001

The separation performance of zigzag air classifier with angle of 90 degrees was studied using narrow size fractions of thin square samples and granular samples. The simulation results of air velocity inside the classifier indicated that the zigzag geometry induces a new pattern consisting of an upward flow and a circulation flow, Experimental results showed that overflow product recovery was described as an integral calculus of normal distribution as a function of dimensionless air velocity ( $V_{A}$ $V_{A50}$), where $V_{A}$ is superficial air velocity and $V_{A50}$ is the $V_{A}$ at the fifty percent recovery. The $V_{A}$ values were predicted using the equations derived from dynamics for a particle dropping in air. A monitoring system that utilizes changes in acoustic signals emitted during the process of air classification was developed to separate PET with desired recovery or grade. The technical feasibility of the on-line monitoring of the PET recovery and grade was demonstrated by measuring relative energy of the signals.signals.als.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.215-223
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• 2010

A seasonal circulation patterns in the Chinju Bay (CB) were suggested from the observed data at two channels of the Noryang Channel (NC) and the Daebang Channel (DC) during the period from 2005 to 2008. The water circulation in the CB is mainly controlled through the NC and the DC. In winter, tidal current at the surface layer of the NC flows from the Kwangyang Bay (KB) eastward into the CB, whereas the current at the bottom layer flows from the CB westward into the KB. In summer, tidal current at the surface layer of the NC goes from the CB westward into the KB. The flow system at the NC shows the typical pattern of thermohaline circulation. In spring, tidal current at the surface layer of the eastern part of the DC flows out into southeastern open ocean. However, in summer, the current in the western part of the DC flows into the CB through the DC. Also, the velocity in the western part of DC is 50~70 cm/sec stronger than that in the eastern part. To obtain better understanding on the seasonal circulation pattern in the NC and the DC, additionally the detailed studies on the field measurements and three dimensional numerical modeling are needed.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.286-293
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• 2005

An interpretation on the solid circulation characteristics in a fluidized-bed process has been carried out as a first step to simulate the dry entrained-bed absorption and bubbling-bed regeneration system for $CO_2$ removal from flue gas. A particle population balance has been developed to determine the solid flow rates and particle size distributions in the process. Effects of principal process parameters have been discussed in a laboratory scale process (absorption column: 25 mm i.d., 6 m in height; regeneration column: 0.1 m i.d., 1.2 m in height). The particle size distributions in absorption and regeneration columns were nearly the same. As gas velocity or static bed height in the absorption column increased, soild circulation rate and feed rate of fresh sorbent increased, however, mean particle diameter decreased in the absorption column. As cut diameter of the cyclone of the absorption column increased, solid circulation rate decreased, whereas feed rate of fresh sorbent and mean particle diameter in the absorption column increased. As attrition coefficient of sorbent particle increased, solid circulation rate and feed rate of fresh sorbent increased but mean particle diameter in the absorption column decreased.