• 동력기계공학회지
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• 제4권4호
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• pp.25-31
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• 2000

This paper represents the vector fields and three dimensional mean velocities in the X-Y plane of cone type swirl gas burner measured by using X-probe from the hot-wire anemometer system. This experiment is carried out at flowrate 350 and $450{\ell}/min$ respectively in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component is focused in the narrow slits distributed radially on the edge of a cone type swirl burner, for that reason, there is some entrainment of ambient air in the outer region of the burner and the rotational flow can be shown in the inner region of the burner because mean velocity W is distributed about twice as large as mean velocity V due to inclined flow velocity ejecting from the swirl vanes of a cone type baffle plate of burner. Moreover, the mean velocities are largely distributed near the outer region of burner within $X/R{\fallingdotseq}1.5$, hence, the turbulent characteristics are anticipated to be distributed largely in the center of this region due to the large inclination of mean velocity and swirl effect.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.5-9
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• 2004

An experimental study is performed turbulent swirling flow behind a crcular cylinder using 2-D PIV technique. The Reynolds number investigated is 15,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the cylinder along the test tube.

• Journal of Advanced Marine Engineering and Technology
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• 제28권1호
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• pp.124-135
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• 2004

An experimental study is performed turbulent flow behind a square cylinder by using 2-D PIV technique. The Reynolds number investigated are 10.000. 30.000 and 50,000. The mean velocity vector, time mean axial velocity turbulence intensity. kinetic energy and Reynolds shear stress behind the cylinder are measured, The numerical method used this study is a CFD code, STAR-CD. The numerical results are compared with these of experimental.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2270-2280
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• 2005

An experimental study is performed for turbulent swirling flow behind a circular cylinder using 2-D PIV technique. The Reynolds number investigated are 10,000, 15,000, 20,000 and 25,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the round cylinder along the test tube. A comparison is included with non swirl flow behind a circular and square cylinder. The recirculation zones are showed asymmetric profiles.

• 수산해양기술연구
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• 제46권4호
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• pp.449-457
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• 2010

This study shows that the vertical migration speed of sound scattering layers (SSLs), which is distributed in near Funka Bay, were measured by 3D velocity components acquired from a bottom moorng ADCP. While the bottom mooring type has a problem to measure the velocity vectors of sound scattering layer distributed near to surface, both the continuous vertical migration patterns and variability of backscatterers were routinely investigated as well. In addition, the velocity vectors were compared with the vertical migration velocity estimated from echograms of Mean Volume Backscattering Strength, and estimated to produce observational bias due to SSLs which is composed of backscatterers such as euphausiids, nekton, and fishes have swimming ability.

• 터널과지하공간
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• 제31권6호
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• pp.508-519
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• 2021

본 연구에서는 발파 시 사람과 주변 환경에 영향을 끼치는 발파진동(peak particle velocity, PPV)을 예측하는 모델을 개발하였다. PPV를 예측하기 위해 kNN(k-nearest neighbors), CART(classification and regression tree), SVR(support vector regression), PSO(particle swarm optimization)-SVR 알고리즘을 이용한 4가지 머신러닝 모델을 개발하고 상호 비교하였다. 머신러닝 모델을 훈련하기 위해 경상남도 창원시에 있는 욕망산을 연구지역으로 선정하고 1048개의 발파 데이터를 획득하였다. 발파 데이터는 천공장, 저항선, 공간격, 최대지발장약량, 비장약량, 총공수, 에멀전비율, 이격거리, PPV로 구성되었다. 훈련된 모델들의 성능을 평가하기 위한 지표 값으로 MAE(mean absolute error), MSE(mean squared error), RMSE(root mean squared error)를 사용하였다. 평가결과 PSO-SVR 모델이 MAE, MSE, RMSE가 각각 0.0348, 0.0021, 0.0458으로 가장 우수한 예측 성능을 나타냈다. 마지막으로 개발된 머신러닝 모델을 이용하여 주변 환경에 영향을 끼치는 정도를 예측하는 방법을 제시하였다.

• Journal of Cardiovascular Imaging
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• 제31권1호
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• pp.41-48
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• 2023

BACKGROUND: The function of left atrium (LA) is difficult to assess because of its ventricle-dependent, dynamic movement. The aim of this study was to assess LA function using velocity vector imaging (VVI) and compare LA function in patients with hypertrophic cardiomyopathy (HCMP) and left ventricular hypertrophy (LVH) with normal controls. METHODS: Fourteen patients with HCMP (72% male, mean age of 52.6 ± 9.8), 15 hypertensive patients with LVH (88% male, mean age of 54.0 ± 15.3), and 10 age-matched controls (83% male, mean age of 50.0 ± 4.6) were prospectively studied. Echocardiographic images of the LA were analyzed with VVI, and strain rate (SR) was compared among the 3 groups. RESULTS: The e' velocity (7.7 ± 1.1; 5.1 ± 0.8; 4.5 ± 1.3 cm/sec, p = 0.013), E/e' (6.8 ± 1.6; 12.4 ± 3.3; 14.7 ± 4.2, p = 0.035), and late diastolic SR at mid LA (-1.65 ± 0.51; -0.97 ± 0.55; -0.82 ± 0.32, p = 0.002) were significantly different among the groups (normal; LVH; HCMP, respectively). The e' velocity, E/e', and late diastolic SR at mid LA were significantly different between normal and LVH (p = 0.001; 0.022; 0.018), whereas LA size was similar between normal and LVH (p = 0.592). The mean late diastolic peak SR of mid LA was significantly correlated with indices of diastolic function (E/e', e', and LA size). CONCLUSIONS: The SR is a useful tool for detailed evaluation of LA function, especially early dysfunction of LA in groups with normal LA size.

• Journal of Advanced Marine Engineering and Technology
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• 제25권6호
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• pp.1195-1202
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• 2001

The flow characteristics in a bifurcated duct are investigated experimentally. Physical properties such as mean velocity vectors, mean x-y stress distributions, mean vorticity and total pressure distributions are Obtained for three different Reynolds numbers(578, 620, 688) Using PIV measurements and CFD analysis. Also, three different rates of discharge Q=26.11 l/min, Q=28.11 $\ell$/min, Q=31.17 $\ell$/min) were selected foy experimental conditions. The results of this study would be useful to the engineer in designing the flow systems for heating, ventilation, air conditioning and wastewater purification plants.

• 수산해양기술연구
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• 제46권2호
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• pp.165-172
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• 2010

This study was performed to estimate the swimming velocity of Pacific saury (Cololabis saira) migrated offshore Funka Bay of Hokkaido using an acoustic Doppler current profiler (OceanSurveyor, RDI, 153.6kHz) established in T/S Ushio-maru of Hokkaido University, in September 27, 2003. The ADCP's doppler shift revealed as the raw data that the maximum swimming velocity was measured 163.0cm/s, and its horizontal swimming speed and direction were $72.4{\pm}24.1\;cm/s$, $160.1^{\circ}{\pm}22.3^{\circ}$ while the surrounding current speed and direction were $19.6{\pm}8.4\;cm/s$, $328.1^{\circ}{\pm}45.3^{\circ}$. To calculate the actual swimming speed of Pacific saury in each bins, comparisons for each stratified bins must be made between the mean surrounding current velocity vectors, measured for each stratified bin, and its mean swimming velocity vectors, assumed by reference (threshold > -70dB) and 5dB margin among four beams of ADCP. As a result, the actual averaged swimming velocity was 88.6cm/s and the averaged 3-D swimming velocity was 91.3cm/s using the 3-D velocity vector, respectively.

• 대한기계학회논문집B
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• 제22권6호
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• pp.874-887
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• 1998

A 2-frame PTV (particle tracking velocimetry) system using the concept of match probability between two consequent image frames has been developed to obtain instantaneous velocity fields. The overall 2-frame PTV system including image pre-processing, tracking algorithm and post-processing routine was implemented to apply to real flows. The developed 2-frame PTV system has several advantages such as high recovery ratio of velocity vectors, low error ratio and small computational time compared with the conventional 4-frame PTV and the FFT-based cross-correlation PIV technique. The 2-frame PTV system was applied to a turbulent channel flow over a rectangular block to check its reliability and usefulness. Total 96 sequential image frames have been captured and processed to get both mean and fluctuating velocity vector fields over the recirculating region. The mean velocity and turbulent intensity profiles were well agreed with hte LDV measurements in the separated region behind the block. Time-averaged reattachment length is about 6.3 times of the block height.