摘要或動機

本實驗主要是探究雙圈圈簡單飛機的飛行原理，歸納圈圈結構對飛行距離、升力的影響，以及氣流流經機體時發生的作用。研究結果如下：一、實際發射，歸納影響滑行距離的變因。1. 前後圈直徑比值約為0.8 時滑行距離為最大。2. 前後圈寬度比值越接近1 時，滑行距離越遠，但影響不大。3. 圈圈間隔在21cm 時，滑行距離最大。二、設置風洞，模擬飛機飛行，測量升力1. 圈圈寬度越大，升力越大。2. 升力最大值出現在圈圈仰角25 度左右，風速越快，升力越大。3. 鋁片仰角在20°時升力最大，升力與角度的關係式為 F = 5×10^?7θ⁴ + 4×10^?5θ³ ? 0.0083θ² + 0.2615θ + 0.13744. 風速越快，升力越大，在仰角20°時升力與風速的關係大約為F = 0.4579V² - 0.9231V +1.4772 。5. 鋁片面寬每增加1cm，升力也增加0.1513gw。前後長每增加1cm，升力即增加0.1263gw。三、設置蒸汽氣流，觀察簡單飛機的氣流場1. 蒸汽流通過圈圈時，會發生附壁現象，而且簡單飛機使氣流往下偏折，飛機得到升力。四、理論演繹︰1. 以康達效應的理論推算出升力，與實際測量得的升力約相等，驗證升力確實由康達理論造成。2. 墊高簡單飛機前圈，使得軸線提高，確實影響了飛行距離，墊高1cm 以內，飛行距離均增加了，以實際的改進證實升力確實是康達效應。This experiment mainly discusses the flying principle of the simple plane which is made up of a straw with two paper circles, one bigger than the other, stuck on both two ends of it. We first launched the simple plane actually and concluded the factors which influenced the sliding distance of the plane, including the distance between two circles, diameter and width of the two circles. Second, we set up a simple wind-tunnel and simulated the flight, in order to measure the strength of lift. Third, we set up the steam air flow and observed the change of the air current in the steam flow while flowing through the plane. The Phenomenon of Wall Enclosing happened and made the flows downward, and the plane gained the lift at the same time. Finally, we deduced that there are two sources of lift and Benoulli's law is not suitable for it. The Coanda Effect can be applied to figure out 54 percent of lift. And the current, blocked by the plane, also offers some lift. In order to prove that the Coanda Effect does effect, we padded the first circle to enlarge the angle of elevation of the axis of the two circles. It really affected the sliding distance of the plane. While the first circle is padded up within 1 cm, the sliding distance of the plane increases. Practical improvement proves that Coanda Effect accounts for the lift.