Aerodynamic properties of an archery arrow
Aerodynamic properties of an archery arrow
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射箭箭的空气动力学特性
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发表时间：
2013
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通讯作者：
H. Sugiura
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作者：
T. Miyazaki;K. Mukaiyama;Y. Komori;Kyouhei Okawa;S. Taguchi;H. Sugiura
描述了两种对射箭(A/C/E；伊斯顿技术产品公司)施加的气动力进行无支撑干涉测量的方法。第一次测量是在带有日本宇宙航空研究开发机构60厘米磁悬浮和平衡系统的风洞中进行的，在该系统中，一支箭被悬挂并通过磁力对抗重力进行平衡。最大风速为45米/S，低于射箭运动员射箭的典型风速(约60米/S)。箭头的边界层在测量的Re数范围内(4.0g×103t<；1.5g×104t；)保持层流，阻力系数约为1.5x×104.第二次测量是通过自由飞行实验进行的。利用两台高速摄像机记录射箭的运动轨迹，并分析其速度衰减率，由此确定射箭的阻力系数。为了研究更大范围内(9.0×10~3×10~3×10~4)阻力系数的Re数依赖关系，我们研制了一种以压缩空气为动力源的射箭系统，它以高达75米/S的任意速度发射A/C/E箭。我们在箭头上安装了两个不同类型的点(桩)(流线型和子弹型)。当Re小于1.2×10~4时，两点边界层均为层流。当Re大于1.2×10~4时，弹丸附着点的阻力系数增大到2.6左右。在相同的雷诺数范围内，流线点的阻力系数有两个值，其下限值约为1.6(层流边界层)，较大值约为2.6(湍流边界层)，证实了点的形状对边界层的层流向湍流转变有重要影响。
Two support-interference-free measurements of aerodynamic forces exerted on an archery arrow (A/C/E; Easton Technical Products) are described. The first measurement is conducted in a wind tunnel with JAXA’s 60 cm Magnetic Suspension and Balance System, in which an arrow is suspended and balanced by magnetic force against gravity. The maximum wind velocity is 45 m/s, which is less than a typical velocity of an arrow (about 60 m/s) shot by an archer. The boundary layer of the arrow remains laminar in the measured Re number range (4.0 × 103 < Re < 1.5 × 104), and the drag coefficient is about 1.5 for Re > 1.0 × 104. The second measurement is performed by a free flight experiment. Using two high-speed video cameras, we record the trajectory of an archery arrow and analyze its velocity decay rate, from which the drag coefficient is determined. In order to investigate Re number dependence of the drag coefficient in a wider range (9.0 × 103 < Re < 2.4 × 104), we have developed an arrow-shooting system using compressed air as a power source, which launches the A/C/E arrow at an arbitrary velocity up to 75 m/s. We attach two points (piles) of different type (streamlined and bullet) to the arrow-nose. The boundary layer is laminar for both points for Re less than about 1.2 × 104. It becomes turbulent for Re larger than 1.2 × 104 and the drag coefficient increases to about 2.6, when the bullet point is attached. In the same Re range, two values of drag coefficient are found for the streamlined point, of which the lower value is about 1.6 (laminar boundary layer) and the larger value is about 2.6 (turbulent boundary layer), confirming that the point-shape has a crucial influence on the laminar to turbulent transition of the boundary layer.