• Journal of Environmental Science International
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• v.21 no.4
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• pp.471-478
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• 2012

In this study, the flow characteristic analysis at the curved-channel of the actual channel section is compared and reviewed using the 2D RMA-2 model and the 3D FLOW-3D model. the curve section with curve rate 1.044 in the research section is analyzed applying the frequency of he project flood of 100 years. According to the result, the issue for the application of the FLOW-3D Model's three-dimensional numeric analysis result to the actual river is found to be reviewed with caution. Also, application of the 3D model to the wide basin's flood characteristic is determined to be somewhat risky. But, the applicability to the hydraulic property analysis of a partial channel section and the impact analysis and forecast of hydraulic structure is presumed to be high. In addition, if the parameters to reflect the vegetation of basin and the actual channel, more accurate topological measurement data and the topological data with high closeness to the current status are provided, the result with higher reliability is considered to be drawn.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.315-319
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• 2010

The near wake of square section cylinders with different corner radii is studied by numerical method to investigate the influence of corner radius. Eight models, R/D=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 (R is the corner radius and D is the characteristic dimension of the body) at Re=500 were studied. The numerical results of St, CD and CL at R/D=0 and R/D=0.5 were compared with experiments to prove the feasibility and also investigate the trend of flow phenomena by the various radius corners. Results indicate that, as R/D ratio is increased, the Strouha lnumber is increased, the minimum pressure point on the cylinder surface moved own stream. The calculated results shows that between R/D=0.15 to R/D=0.3 have CD and CL.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.657-658
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• 2006

Recently, the micro on-off valves have been focused on core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for bio-medical applications. A key characteristics for micro valve, operated by compressed air, are high speed response and great repeatability. Indeed, it is also important to keep the pressure on the cross-sectional area of the poppet to be constant regardless of the fluctuation of the pressure exerted on the ports. In this study, we have designed and analysed the high-speed and high flow rate micro on-off valve using the analogy of equivalent magnetic circuit and Finite Element Method(FEM) respectively. In case of poppet, flow field characteristic was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D distribution curve of the force by working the front poppet.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.33-40
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• 2004

A 4D-PTV system was constructed. The measurement system consists of three high-speed high-definition cameras(1k x 1k, 2000fps), Nd-Yag laser(2000Hz) and a host computer. The GA-3D-PTV algorithm was used for completing the measurement system. The 4D-PTV is capable of probing the spatial distribution of velocity vectors of the flow field overcoming the temporal resolution of the characteristic turbulence length scales of the measured flow fields. A horizontal impinged jet flow (H/D=7) was measured. The Reynolds number is about 33,000. Spatial temporal evolution of the jet flow was examined and physical properties such as spatial distributions of vorticity and turbulent kinetic energy were obtained with the constructed.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.2
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• pp.101-109
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• 1998

Hydraulic property of fissured aquifers often depends on geologic structure which acts main channel of groundwater flow. We treated theories of linear flow related to vertical geologic structure. Then, we analyzed the result of two pumping tests conducted in Okmyeong-ri area (Kyeongbook province) using fractal model and found hydraulic characteristic of the fissured aquifer in this area. According to the pump test analyses, groundwater flow around the holes (pumping well D9; observation wells C3 and D7) of test 1 is linear. and is controlled by vertical geologic structure with infinite length and infinitesimally small width. On the other hand, around the hole D10 (pumping well) of test 2, groundwater flow is pseudo-radial (n=1.9) or radial (n=2). Thus, the characteristic of fractured aquifer often shows variable groundwater flow spatially and temporally.

• Journal of the KSME
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• v.16 no.2
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• pp.84-91
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• 1976

An experimental investigation of the natural circulating boiling flow characteristic in three cases of annulus with different outer diameter, and the effect of annular gap size on the burnout behavior is presented. The experimental work was conducted for each case of test section at system pressure of $1kg/cm^2$ and inlet subcooling $0-20^{\circ}C$ in the full range of throttling ratio. As the result, the following facts were found. 1) With the increase of ${\Delta}T_{sub}$, $D_{2}$ and A/A_{o}$, $q_{BO}$ increases on the whole, and with the decrease of ${\Delta}T_{sub}$ and $D_{2}$, hydrodynamic instability is accelerated to happen prematually. 2)With the increase of ${\Delta}T_{sub}$, $D_{2}$ and A/A_{o}$ burnout characteristic shows the high velocitylow quality burnout, and with the decrease, low-velocity-high quality burnout. 3)With the decrease of A/A_{o}$, hyddrodynamic instability is singnificantly restrained and the difference of $q_{BO}$ in each $D_2$ under same condition is gradually reduced, finally converging into $1.9{\times}10^{5}kcal/m^{2}-hr$.

• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.177-186
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• 2010

In 3D ultrasound color Doppler imaging (CDI), 8-16 pulse transmissions (ensembles) per each scanline are used for effective clutter rejection and flow estimation, but it yields a low volume acquisition rate. In this paper, we have evaluated three flow estimation methods: autoregression (AR), eigendecomposition (ED), and autocorrelation combined with adaptive clutter rejection (AC-ACR) for a small ensemble size (E=4). The performance of AR, ED and AC-ACR methods was compared using 2D and 3D in vivo data acquired under different clutter conditions (common carotid artery, kidney and liver). To evaluate the effectiveness of three methods, receiver operating characteristic (ROC) curves were generated. For 2D kidney in vivo data, the AC-ACR method outperforms the AR and ED methods in terms of the area under the ROC curve (AUC) (0.852 vs. 0.793 and 0.813, respectively). Similarly, the AC-ACR method shows higher AUC values for 2D liver in vivo data compared to the AR and ED methods (0.855 vs. 0.807 and 0.823, respectively). For the common carotid artery data, the AR provides higher AUC values, but it suffers from biased estimates. For 3D in vivo data acquired from a kidney transplant patient, the AC-ACR with E=4 provides an AUC value of 0.799. These in vivo experiment results indicate that the AC-ACR method can provide more robust flow estimates compared to the AR and ED methods with a small ensemble size.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1549-1554
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• 2015

This study examined experimentally the characteristics of the flow pattern and particle suspension in an agitated vessel with a bottom baffle. A flow pattern of the particles was shown to increase the upward flow from the center of the agitated vessel bottom. The suspended particles from the experiment found that the particle suspension was promoted by the development of an Ekman boundary layer. The optimal conditions of the impeller, and the agitated vessel bottom baffle within the experimental range were as follows: Impeller, $n_p=6$, d/D=0.5, and b/d=0.3; and bottom baffle, $n_b=6$, $d_b/D=0.5$ and $b_w/D=0.05$.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.51-57
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• 2013

The length and position of the inlet port on the double tube heat exchanger is analyzed by CFX ver.11 for studying the characteristic of its flow distribution. When the boundary conditions of the inlet temperature and mass flow rate were each $20^{\circ}C$ and 10 ~ 50 kg/min, 3 models that are based on the distance between the inlet port and the center of the heat exchanger(0, 5.025, 10.05 mm) were analyzed to find the uniformity of the flow rate. Based on the flow rate, 4 lengths (23.723, 33.890, 44.057, 57.274 mm) were used to study the flow distribution according to Reynolds Number. The results show that, when the distance from the inlet to the position of the center of the heat exchanger is 10.05 mm and the length is 57.274 mm, the flow distribution is the most unified.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.3
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• pp.251-256
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• 2009

In this research, we experimentally studied flow characteristic by applying PIV measuring techniques which could measure the point velocity of all flow field and measuring the unsteady velocity of surrounding disk generated in a short time. Time range of great velocity change following quick closing of the slide valve was within 0.1s and the cycle was presumed to be 0.12s as a result of comparison study between the result of point flow field and of existing pressure change. Also, surrounding disk flow inside the circular pipe was closed from the upper part and flow road was getting narrow and advanced to the lower part incidentally quickly there was a tendency that the size of the flow back velocity to the upper part immeadiately after the closure decreased to 4/120s and increased again. There was flow back velocity component in y/D=0.2 lower part by the influence of flow back to the upper part after complete closure and the vortex flow of 0.2D-size near y/D=0.7, x/D=-0.3 was observed.