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패러글라이더 캐노피의 유동박리 특성에 대한 실험적 연구
신정한(Jeonghan Shin),채석봉(Seokbong Chae),신이수(Yisu Shin),김주하(Jooha Kim) 한국가시화정보학회 2020 한국가시화정보학회지 Vol.18 No.3
In the present study, we investigate the flow separation characteristics of a paraglider canopy model by tuft visualization. The experiment is conducted at Re = 3.3×105 in a wind tunnel large enough to contain the three-dimensional paraglider canopy model, where Re is Reynolds number based on the mean chord length and the free-stream velocity. The flow separation characteristics of the canopy model near the wing root are similar to those of a two-dimensional airfoil with a cross-section similar to the model. On the other hand, near the wingtip region, the flow separation is suppressed by the downwash induced by the wingtip vortex. As a result, as the angle of attack increases, the flow separation occurs from the wing root region of the canopy model and develops toward the wingtip.
신정한(Jeonghan Shin),채석봉(Seokbong Chae),신이수(Yisu Shin),박정목(Jungmok Park),송진석(Ginseok Song),김주하(Jooha Kim) 한국가시화정보학회 2021 한국가시화정보학회지 Vol.19 No.3
In the present study, we investigate the flow characteristics of a paraglider canopy with leading-edge tubercles by performing force measurement and surface flow visualizations. The experiment is conducted at Re = 3.3×10<SUP>5</SUP> in a wind tunnel, where Re is the Reynolds number based on the mean chord length and the free-stream velocity. The canopy model with leading-edge tubercles has flow characteristics of a two-step stall, showing an earlier onset of the first stall than the canopy model without leading-edge tubercles. However, the main stall angle of the tubercled model is much larger than that of the canopy model without tubercles, resulting in a higher aerodynamic performance at high angles of attack. The delay in the main stall is ascribed to the suppression of separation bubble collapse around the wingtip at high angles of attack.
신이수(Yisu Shin),신정한(Jeonghan Shin),채석봉(Seokbong Chae),김주하(Jooha Kim) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
In the present study, a flow visualization experiment was conducted on a paraglider canopy with a form of a curved airfoil. The experiment was performed at Re = 3.3 ×10<SUP>5</SUP> and the angles of attack of 0° to 14°. It was observed that flow separation did not occur on the canopy surface at a low angle of attack, and a flow separation region grew from the center of the canopy surface at a high angle of attack. By comparison with the model of this experiment and the NACA 23021, which has the most similar cross section, the change of the local Reynolds number by the chord length of the canopy was shown to have no significant effect on the flow characteristics of the canopy. The present study showed that the dominant parameter affecting the flow-separation characteristics is the spanwise variation of the local angle of attack caused by the curvature of the canopy.