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Surface flow control by leading-edge tubercles on a paraglider canopy
J. Shin(신정한),S. Chae(채석봉),Y. Shin(신이수),S. Hwang(황성윤),J. Park(박정목),G. S. Song(송진석),J. Kim(김주하) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Since paragliders repeat ascending and descending flights, it is essential to improve the aerodynamic performance of a canopy (i.e., a wing of paraglider) over a wide range of angles of attack. In this study, we implement the tubercle structure on the leading edge of a humpback whale flipper, which is known to delay the onset of stall, to the canopy model dynamically similar to Boomerang 11 (Gin Gliders) for controlling the flow over the model. The surface flow on the canopy model is experimentally visualized by using tuft visualization technique at Re = 3.3×10<sup>5</sup>, where Re is the Reynolds number based on the mean chord length and the free-stream velocity. For both the canopy models with and without the leading-edge tubercles, the separated region is formed around the mid-span of the model at a high angle of attack because both the local angle of attack and the local chord length decreases towards the tip of the canopy model. The separated region extends from the trailing to the leading edge on the upper (suction) surface as the angle of attack increases. The leading-edge tubercles are shown to prevent the extension of the separated region towards the leading edge, thus substantially reducing the size of the separated region formed around the mid-span section. On the other hand, it is found that the leading-edge tubercles rather induce the flow separation near the tip region. Based on the above results, a strategy to effectively control the flow over a paraglider canopy will be suggested in the presentation.
선단 돌기가 적용된 패러글라이더 캐노피의 공력성능에 대한 실험적 연구
신정한(J. Shin),채석봉(S. Chae),신이수(Y. Shin),황성윤(S. Hwang),박정목(J. Park),송진석(G. Song),김주하(J. Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The stall frequently occurs during the paraglider flight because the paraglider has wide range of angle of attacks due to repetition of ascending and descending flights. In this study, we apply the tubercle structure the leading edge of a paraglider canopy model dynamically similar to Boomerang 11 (Gin gliders). The tubercle structure is from a humpback whale flipper, which is known to delay the stall. The aerodynamic performances of the canopy with and without the leading-edge tubercles are experimentally measured by load cell at Re = 3.3×10<SUP>5</SUP>, where Re is the Reynolds number based on the mean chord length and the free-stream velocity. The leading-edge tubercles delay the stall and increase the lift coefficient on low angle of attack. Based on the above result, a role of the leading-edge tubercles will be explained with flow visualization data in the presentation.