低雷諾數下拍撲翼飛行特性之數值研究

Numerical Approach to the Aerodynamic Characteristics of Low Reynolds Number Flapping-Wing Motion

苗志銘(Jr-Ming Miao) ； 何明輝(Ming-Hui Ho) ； 戴昌賢(Chang-Hsien Tai)

《中國航空太空學會學刊》 37卷2期 (2005/06) Pp. 135-146

https://doi.org/10.6124/TAASRC.200506_37(2).04

摘要

近年飛行生物拍撲運動空氣動力學之研究顯示，針對此類週期性且複雜運動形態的流場現象，採用“非穩態分析”是必要的手段。本文即針對蜻蜒翼翅非穩態拍撲運動，採1:8橢圓薄翼依實體單翼進行二維暫態氣動力特性數值模擬，籍由簡化運動姿態爲平移及旋轉複合機構，在非穩態流場中考量翼翅運動並結合動態網格技術控制網格變形，以非定常且層流模式求解雷諾均值Navier-Stoke''''s方程式，重點在於分析拍撲運動下所産生的升力與推力。模擬結果顯示，以一致性複合式動態網格技術可以有效地分析昆蟲翼翅真實動態拍撲運動下所引發不同瞬間之升、推力變化特性，分析現象與實驗觀察之推論相符。本文依此爲根基，以不同翼翅厚度作進一步研究，探討1:4，1:8及1:12橢圓薄翼在相同拍撲運動下之低雷諾數氣動力特性，數據顯示厚度越薄則其氣動效率越佳，可見薄翼除了昆蟲生理特性、重量負荷等之限制因素之外，在氣動力之影響有其正面之效益。

關鍵字

數值模擬 ； 動態網格技術 ； 低雷諾數

並列摘要

Recently, a lot of experimental researches showed that the unsteady flow analysis is a necessary procedure for modeling the complicated aerodynamic characteristics of insects with flapping wings. The purpose of this paper is intended to systematically model both the lift and thrust forces that are produced by flapping motion of elliptic wing by CFD method with dynamic mesh technology. The test model is an oval wing with ratio of long axis to short axis equal to 1:8. The trajectory of flapping wing in space with time was simply expressed as a formula that is a combination of translational and rotational motion. Dynamic mesh technique is also employed in present numerical code to model the continuous flapping motion of airfoil. Unsteady, laminar flow fields around the flapping wing are computed by solving the Navier-Stokes governing equation under low Reynold number condition with control-volume method. The computational domain is constructed with a conformal hybrid mesh system. The effect of wing's thickness on the aerodynamic performance of elliptic wings was discussed in this study. The lift force and thrust force produced by three different wing's aspect ratios of 1/4, 1/8 and 1/12 were evaluated with the same described flapping motion. Present results showed that the aerodynamic efficiency is higher as the aspect ratio of elliptic wing is smaller.

並列關鍵字

Numerical simulation ； Dynamic mesh technique ； Low Reynold number