활강/활공 단계의 스키점프 선수 주위 유동의 큰 에디 모사

Abstract

Investigation of flows over ski jumper is important to control their posture, which is essential to achieve a longer flight distance. For this purpose, we conduct a large eddy simulation (LES) of turbulent flow past a model of a ski jumper which is obtained by 3D scanning the ski jumpers body (Mr. Chil-Ku Kang, a member of the Korean national ski jump team). In flight posture, the angle of attack of the jump ski is 30° and the Reynolds number based on the length of jump ski ( ) and the flight velocity ( ) is 5.4 × 105, and in-run posture the Reynolds number based on the height of posture ( ) and the sliding velocity ( ) is 1.8 × 105. The flow statistics including the drag and lift coefficients during the flight and in-run phases are in good agreements with our own experimental data in each posture. We investigate the flow characteristics such as the stagnation region, flow separation, and three-dimensional vortical structures and their effects on the drag, lift, and lift/drag. To find the optimal flight posture of the ski jumper, we build a simple geometric model of a ski jumper based on the result of LES where each part of the ski jumpers body is modeled as a canonical bluff body such as a sphere, cylinder and flat plate. The drag and lift obtained from this approach are in good agreements with those from LES. Also, using this approach, the optimal flight posture for the best aerodynamic performance is to be found.