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Weis-Fogh형 선박 추진기구의 개발 유동장의 가시화 및 수치해석
노기덕 대한기계학회 1993 대한기계학회논문집 Vol.17 No.2
The flowfield of Weis-Fogh type ship's Propulsion is visualized by numerical simulations using the discrete vortex method and by the hydrogen bubble technique. The simulations are performed by assuming that the separations occur at the trailing edge of the wing. The streak lines and time lines are calculated by introducing the tracers at adequate intervals. They agree well with experimental results. The flowfield is unsteady and complex, but the properties of the flow are clarified by numerical and experimental visualization.
Three dimensional aerodynamic characteristics of weis-fogh mechanism
노기덕 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.1
The three-dimensional flows in the Weis-Fogh mechanism are studied by flow visualization and numerical simulation by the discrete vortex method. The vortex method, especially the vortex stick method, is employed to investigate the vortex structure in the wake of the two wings. The pressure is estimated by the Bernoulli equation, and the lift on the wing is also obtained. For the results, the eddies near the leading edge of each wing in the fling stage take a convex shape because the eddies shed from both tips entrain the flows, and the downwash in the rotating stage is deflected toward the outside because the outside tip vortex is stronger than the inside one. The lift coefficient on the wings in this mechanism is almost independent of the Reynolds number.
Drag reduction from fences on a square prism near plane wall
노기덕,Baoshan Zhu 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12
The suppression of fluid force acting on a square prism near a plane wall was studied by attaching fences to the corners of the prism. The height of the fences was 10% of the square width and the Reynolds number considered was Re=2.0×10⁴. The experimental parameters were the attachment location and number of fences, the gap ratio G/B (G/B=0.1~1.2) to the prism. The average drag coefficients were increased and the average lift coefficients decreased and increased with the gap ratios toward the plane wall. The drag of the prism was reduced by 7.6% on average with the gap ratios by attaching a normal fence at the upper rear corner and a horizontal fence at the lower rear corner of the prism. By conducting a visualization experiment, it was noticed that the vertical fence installed at the upper rear edge generated a clock-wise vortex past the fence and reduced the separation region.