- 學位論文
拍撲翼材質對渦流場之影響
The Effect of Material of a Flapping Wing on the Strength of the Vortices Generated
摘要
本文著力於拍翼翅膀材質與流場量測研究。透過使用PIV流場量測系統，觀察撲翼之流場變化，並改變翅膀材質，探討其間之改變。根據實驗結果顯示，不同厚薄度的翅膀其流場中渦流成長及消散之情形類似。藉由雷射切面影像觀測流場，可知翅膀在拍動過程中，翼尖部分之渦流較小，翅膀中段附近之渦流面積最大也最為明顯，而後，越接近翼根處渦流面積越小。此變化可能與翅膀各位置之壓力差有關。 在三組厚薄度不同的翅膀中，其第一組之翅膀由於受到較大之變形問題，流場較其他兩組不穩定。改變材質後之兩組翅膀，不論在生成或結合渦流都非常快速。第三組可能是由於厚度的負擔，在拍動過程中造成了較大之阻力。雖其產生之渦漩範圍是最大，但流場之穩定度卻不及第二組。以第二組整體效果最佳，對此實驗之拍撲機構為最理想之選擇。
並列摘要
This thesis is mainly about the flexible flapping-wing mechanism and it’s related studies. The flow visualization experiments revealed a three-dimensional flow. Details of this flow pattern were studied with a flapping mechanism and used the PIV experimental technique to perform it. A high speed camera captured the images by a laser. The images used to study the velocity fields, as obtained by simultaneous vortex measurements. At last, this thesis did the compare with the flow field by these different flexible wings. The vortex development is studied for various wings, at various thickness and at various spanwise positions. The existence of vortices developing during the flapping cycle have the similar situations between the three models. The flexible wing design leads to various unsteady aerodynamic phenomena and due to the flexible wings there is a strong fluid structure interaction. This variation will affect the flight stability. When the wing start to upstroke flight, the growth of the vortex with time and separated when the wing start to downstroke flight, and then quickly merged into a larger one. The leading-edge vortex increasing in size from wingtip to the middle of the wing. Between 30 and 50% of the wing length, the vortex had the biggest area, and then the diameter decreased from the middle wing to the wingbase. This variation may be related to the different pressure on each position of the wing. According to the experiments, the first model has the most flexible wing. It shows that the first model has the worst flight stability and the the second model is the best selection of the flapping mechanism. A better understanding of these effects can help to understand and further improve the design of the flexible wing.