Effect of initial attitude on autorotation flight of maple samaras (Acer palmatum)
Effect of initial attitude on autorotation flight of maple samaras (Acer palmatum)
复制标题
初始姿态对翅果自转飞行的影响
DOI：
10.1007/s12206-016-0129-2
复制
发表时间：
2016
影响因子：
1.6
通讯作者：
Sang
中科院分区：
文献类型：
--
作者：
E. Lee;Sang
许多翅果或有翼的种子，如枫树种子，在坠落过程中会自动飞行。自旋枫种子下降速度慢是由于种子叶片前缘涡产生的高升力引起的。枫树种子在脱离母体后，不论其初始姿态如何，其自旋飞行都非常稳定。实验研究了初始姿态对自旋枫种子降落速度、旋转速度和转角等飞行特性的影响。根据初始姿态，从初始分离到稳态自旋的过渡飞行是清晰可辨的。它从种子基部朝下开始，然后通过改变种子的俯仰角和锥角来接近平衡。下表面朝下，翻滚到前缘朝下的状态。在六种初始姿态测试中，种子下表面朝下稳定速度最快。大多数枫种子属于下表面朝下的情况。结果表明，与初始姿态无关，枫树种子在与亲本植物分离后，在660 mm的距离内进行稳定的自旋。
Many samaras or winged seeds such as maple seeds make an autorotational flight during their falling. Slow descent speed of autorotating maple seeds has been known to be caused by the high lift generated by Leading-edge vortex (LEV) on the seed blade. The autorotation flight of maple seeds is observed to be very stable after detaching from their parent plants, regardless of their initial attitude. In this study, the effects of initial attitude on the flight characteristics of autorotating maple seeds, such as descending velocity, rotational speed and coning angle were investigated experimentally. Depending on the initial attitude, the transitional flight from the initial detachment to the steady-state autorotation is clearly discernible. It starts with downward facing of the seed base, and then approaches equilibrium by changing the pitch and coning angles of the seed. The lower surface faces downward and tumbles to the downward facing state of the leading edge. Among the six initial attitudes tested, the downward facing of the seed’s lower surface exhibits the fastest stabilization. Most maple seeds belong to the case of downward facing of lower surface. The present results demonstrate that the maple seeds make a stable autorotation within a distance of 660 mm after detaching from their parent plants, regardless of their initial attitude.