- 學位論文
仿生擺振運動撓性翼之受力量測及分析
The Measurement and Analysis of Force for Biomimetics of Flexible Airfoil in Oscillating Motion
摘要
魚類經過長時間的演化，發展出巧妙的推進方法。因此本文以研究仿生魚游擺尾運動的受力情形為目標，使用NACA0012撓性翼藉由拖曳式水槽、機械手臂與伺服馬達的控制，成功地作出週期性的擺振運動，藉此模擬實驗魚類的擺尾運動。本研究固定拍動振幅 以及雷諾數 ，改變史徹赫數 間隔0.05和擺動角度 間隔 ，藉此探究對推進力及升力的影響。研究發現擺振頻率越高推進力越高，而大擺動角度相對小擺動角度有較大推力峰值的生成，但在小擺動角度且高速拖曳時能有效地減阻並維持較好的推力係數。 透過文獻回顧，撓性翼和剛性翼在推進係數的影響上並無太大差別，因此本文使用部分與實驗相同的參數進行剛性翼數值模擬並透過力元理論分析，比較結果顯示，實驗和數值計算的結果差異不大，足以確認實驗與數值結果。本文利用力元理論的概念，將受力分解並且量化為四個物理項，分別為翼板加速度項、翼板運動速度項、 環境渦度項、和翼板表面渦度項。藉此瞭解主要影響推進機制的關鍵，並且找出在不同參數下各項所佔的比例。本研究發現翼板運動的加速度以及流場環境渦度為主要的推進力的來源。
並列摘要
The longstanding evolution has ensured fish which developed the smart propulsion system. This thesis focuses on the force status of Bionic fish swimming in flapping tail motion. Simulating fish flapping tail motion with Naca0012 flexible airfoil undergo pe-riodic oscillating motion by controlling Single-Axis robot and servo motor at the tow tank. Experiments are performed at a fixed value of the heave amplitude and of the Reynolds number to investigate the effects of variations of the Strouhal number by a step of 0.05 and of the maximum pitch angle by a step of . The experimental result indicates that the higher oscillating frequency produces the higher thrust coefficient. Moreover, it is found that the oscillat-ing motion with a high pitch angle produces larger maximum transient peak thrust than a small pitch angle. However, keeping the greater thrust coefficient in the small pitch angle and high-speed towing that can efficiently reduce drag. According to the literature review, flexible airfoil affects the thrust coefficient in-distinctly relative to rigid airfoil. Therefore, through force elements theory, we can carry out numerical simulations of rigid airfoil with same parameters to observe various force elements contributions. Comparisons between numerical and experimental results show that the trends of total lift and thrust under some conditions are similar. Here, we also decompose and quantify the force into four components: the contribution associated with the acceleration of the airfoil; the contribution by the velocity of the airfoil; the contribution by the surface vorticity and friction on the airfoil; the contribution of pres-sure force due to vorticity within the flow field. This theory identify the main sources of the propulsion system and proportion of the components in the different parameters. The results indicate that acceleration term and vorticity of the flow field term play a rule key in high thrust production in a full flapping.