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남청도,Nam, Cheong-Do 한국마린엔지니어링학회 1991 한국마린엔지니어링학회지 Vol.15 No.3
This paper describes characteristics of the flow pattern of the flow past a rectangular cylinder experimentally investigated. The width-to-length ratio of the section varried from 2 to4. For the statistical treatment, autocorrelation coefficient, probability density function and power spectral density function are obtained by the digital processing technic through on-line system with a hot wire anemometer. As a results, it was found that strong periodic coherent eddies structure is sustained to about 20H downstream from the cylinder. And nearer the cylinder in the wake, the number of turbulent eddies of a large scale coherent structure are comparatively much more dominant than that of a small scale one. By the analysis of power spectrum, It was cleared that there exists a certain range of the width to length ratio between 2.5 and 3 of which the flow pattern changes abruptly with a sudden discontinuity in Strouhal number.
BEMT를 적용한 20kW 수평축 풍력터빈 형상설계 및 성능해석
강호근,남청도,이영호,김범석,Kang, Ho-Keun,Nam, Cheong-Do,Lee, Young-Ho,Kim, Beom-Seok 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.6
The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) is developed by use of BEMT, which is the standard computational technique for prediction of power curves of wind turbines. The Prandtl's tip loss theory is adopted to consider the blade tip loss. The lift and the drag coefficient of S-809 airfoil are predicted via X-FOIL and the post stall characteristics of S-809 also are estimated by the Viterna's equations.$^{[13]}$ All the predicted aerodynamic characteristics are fairly well agreed with the wind tunnel test results. performed by Sommers in Delft university of technology. The rated power of the testing rotor is 20kW(FIL-20) at design conditions. The experimental aerodynamic parameters and the X-FOIL data are used for the power Prediction of the FIL-20 respectively The comparison results shows good agreement in power prediction.
BEMT를 적용한 수평축 풍력터빈 성능해석 소프트웨어의 개발
김범석(Kim, Beom-Seok),남청도(Nam, Cheong-Do),이영호(Lee, Young-Ho) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.11
The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) was developed by use of BEMT. The Prandtl's tip loss theory was adopted to consider the blade tip loss. The lift and the drag coefficient of S-809 airfoil were predicted via X-FOIL and also the post stall characteristics of S-809 were estimated by the Viterna's equations. All the predicted aerodynamic characteristics are fairly well agreed with the wind tunnel test results, performed by Sommers in Delft university of technology. The rated power of the testing rotor is 20kW(FIL-20) at design conditions. The experimental aerodynamic parameters and the X-FOIL data were used for the power prediction of the FIL-20 respectively. The comparison results shows good agreement in power prediction.
김유택(You-Taek Kim),남청도(Cheong-Do Nam),강호근(Ho-Keun Kang),이영호(Young-Ho Lee) 한국유체기계학회 2004 유체기계 연구개발 발표회 논문집 Vol.- No.-
A screw-type centrifugal pump was manufactured to cany solids primarily and its impeller has a wide flow passage. However, the effect of flow passage shape on delay of the choke due to entrained air has not been clarified yet. Moreover, because its impeller has a particular shape, only few studies have tried to clarify the pump performance and details of internal flow pattern of that pump. For that reason, we carried out the pump performance experiment under air-water two-phase flow condition with different impeller tip clearances, pump rotational speeds and void fractions by using a small screw-type centrifugal pump designed to acquire basic data. In a general centrifugal pump, it was reported that loss of pump head from single-phase flow to the choke due to air entrainment near the best efficiency point was large. However, the loss near the best efficient point in a screw-type centrifugal pump became less than that in a general centrifugal pump.
강신정(Shin-Jeong KANG),마모루 타나하시(Mamoru TANAHASHI),도시오 미야우찌(Toshio MIYAUCHI),남청도(Cheong-Do NAM),이영호(Young-Ho LEE) 한국전산유체공학회 2001 한국전산유체공학회 학술대회논문집 Vol.2001 No.-
The flow past a circular cylinder forced to vibrate transversely is numerically simulated by solving the two-dimensional Navier-Stokes equations modified by the vibration velocity of a circular cylinder at a Reynolds number of 164. 'The higher-order finite difference scheme is employed for the spatial discretization along with the second order Adams-Bashforth and the first order backward-Euler time integration. The calculated cylinder vibration frequency is between 0.60 and 1.30 times of the natural vortex~shedding frequency. The calculated oscillation amplitude extends to 25% of the cylinder diameter and in the case of the lock-in region it is 6.0%, It is made clear that the cylinder oscillation has influence on the wake pattern, the time histories of the drag and lift forces, power spectral density and phase diagrams, etc. It is found that these results include hath the periodic (lock-in) and the quasi-periodic (non-lock-in) state. The vortex shedding frequency equals the driving frequency in the lock-in region but is independent in the non-lack-in region. The mean drag and the maximum lift coefficient increase with the increase of the forcing amplitude in the lock-in state. The lock-in boundaries are also established from the present direct numerical simulation.
모장오(Jang-Oh MO),강신정(Shin-Jeong KANG),송근택(Geun-Taek SONG),남청도(Cheong-Do NAM),이영호(Young-Ho LEE) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
A commercial CFD code is applied to analyze the 3-D viscous flow field within vertical multi-stage centrifugal pump including impeller with 6 blades and guide vane with 11 blades and is performed by changing flow rate from 10 to 26㎥/h at the constant 3500rpm. The purpose of this 3-D numerical simulation is not only to confirm how much the effect of three kinds of blade inlet breadth (11㎜, 11.5㎜, 12㎜) of impeller has influence On the performance of vertical multi-stage pump but also to make clear the cause about performance difference at the exit side of impeller and guide vane. The vertical multi-stage pump consisit of the impeller, guide, vane and cylinder. The grid of numerical analysis used to the vertical multi-stage pump is 18,000, 45,000, and 100000 cells in case of the impeller, guide vane, cylinder and total grid is 730,000 cells. The characteristics such as total pressure coefficient, total head, shaft horse power, power efficiency at the exit side of impeller and guide vane, discharge coefficient are represented according to flow rage changing.
모장오(Jang-Oh Mo),강신정(Shin-Jeong Kang),김유택(You-Taek Kim),남청도(Cheong-Do Nam),이영호(Young-Ho Lee) 한국해양대학교 해사산업연구소 2002 海事産業硏究所論文集 Vol.12 No.-
A commercial CFD code is applied to analyze the 3-D viscous flow field within the impeller of centrifugal pump. Design conditions are based on 75% of design efficiency. Two design conditions (Case1, Case2) with the different blade number and blade outlet breadth are performed by changing flow rate from 8 to 26 ㎥/h at the constant 3500 rpm. The characteristics of Case1 and Case2 such as total pressure coefficient, total head, shaft horse power, power efficiency are represented due to flow rate changing at the 50% position of span direction.