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최윤호,최용준,김주철,정관수,Choi. Yun-Ho,Choi. Yong-Joon,Kim. Joo-Cheol,Jung. Kwan-Sue 한국방재학회 2011 한국방재학회논문집 Vol.11 No.3
본 연구에서는 대상유역을 지표면과 하천 격자로 분할한 후, Manning 식을 기반으로 각 격자 중심에서 유역 출구점까지의 유하시간을 계산하여 등시간별 체적유량을 산정하였으며, 이로부터 유역의 동수역학적 특성인 특성유속을 고려한 직접유출수문 곡선을 도출하였다. 대상유역은 보청천유역의 산성유역을 선정하였다. 대상유역에 대한 매개변수 산정 결과 흐름누적값은 3800, K는 3.3으로 결정되었다. 보정된 매개변수를 실제사상에 대해 적용하여 검증한 결과 첨두유량과 첨두시간의 평균 절대오차는 각각 3.41%, 0.67 hr로 비교적 양호한 모의결과를 나타냈다. 또한 유효우량에 따른 유하시간별 기여면적 주상도를 분석한 결과 본 연구에서 적용된 모형은 강우강도에 따른 유역의 수리학적 특성을 잘 표현하고 있음을 알 수 있었다. In this study, after the target basin was divided into both overland and channel grids, the travel time from center of each grid cell to watershed`s outlet was calculated based on the manning equation. Through this process, volumetric discharge was calculated according to the isochrones and finally, the direct runoff hydrograph was estimated considering watershed`s hydrodynamic characteristics. Sanseong subwatershed located in main stream of Bocheong basin was selected as a target basin. The model parameters are only two: area threshold and channel velocity correction factor; the optimized values were estimated at 3,800 and 3.3, respectively. The developed model based on the tuned parameters led to well-matching results between observed and calculated hydrographs (mean of absolute error of peak discharge: 3.41%, mean of absolute error of peak time: 0.67 hr). Moreover, the analysis results regarding histogram of travel time-contribution area demonstrates that the proposed model characterizes relatively well hydrodynamic characteristics of the catchment due to effective rainfall.
원심압축기용 베인 디퓨저 내부유동의 수치해석 및 성능평가
최윤호,강신형,이장춘,Choi, Yun-Ho,Kang, Shin-Hyoung,Lee, Jang-Chun 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.10
A three dimensional compressible Navier-Stokes code is developed to analyze flowfields and performance of a vaned diffuser in a centrifugal compressor. It employs scalar implicit approximate factorization, finite volume formulation, second order upwind differencing and a two-equation $q-{\omega}$ turbulence model based on the integration to the wall. Pressure recovery and loss coefficients of a vaned diffuser are evaluated using a developed computer code. The simulated three dimensional flows show how through flow structure affects pressure recovery performance and loss coefficients of a vane for design and off-design inlet flow angles. Development of complex three dimensional flow over the inlet region and leading edge are very influential to the overall flow and performance.
미지의 방향성을 갖는 상호 연결된 비선형 시스템에 대한 최소 함수 근사 기반 분산 적응 제어
최윤호(Yun Ho Choi),유성진(Sung Jin Yoo) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.4
A minimal-function-approximation-based control approach is presented for the decentralized adaptive tracking of interconnected nonlinear systems consisting of subsystems with unknown control directions. The main contribution of this paper is to solve the utilization difficulty of the Nussbaum function caused by unusable error surfaces in the minimal-approximation-based control framework. The stability of the closed-loop system is rigorously analyzed in the Lyapunov sense and simulation results are provided to demonstrate the effectiveness of the proposed control algorithm.