二維準定常拍翼流場及其泡膜顯像

2D Quasi-Steady Flow around a Flapping Wing and Its Bubble-Film Flow Visualization

黃心綸(Hsin-Lun Haung)

指導教授 ： 楊龍杰

淡江大學/工學院/機械與機電工程學系碩士班/碩士(2014年)

https://doi.org/10.6846/TKU.2014.00346

摘要

本研究提出以10cm拍翼機進行二維準定常流模擬分析以及以立體攝影術擷取移動邊界。軌跡擷取使用SURFER和GAMBIT將立體攝影的三維軌跡擷取出二維的1/4翼展並生成網格。在Fluent中進行流場模擬，其中準定常CFD模擬在Fluent中被視為二維移動邊界。流場設定上，上風速度在拍翼流場中也得到新的考量。最後計算含有時變的二維流場與對應的升力係數。從拍翼頻率40Hz下一週期之升力係數呈現出與風洞數據及PVDF現地量測數據相似之結果。
本研究開發並測試出一套新的方法，即是利用泡膜觀察拍翼流場。此研究是基於泡膜干涉之概念，其中不同厚度的泡膜將呈現出不同色彩。10cm翼展拍翼機在泡膜中作動，並且以一台彩色CCD捕捉泡膜色彩變化圖案。將影像送入MATLAB來生成每個像素的RGB值，並且對應標準泡膜厚度色卡之厚度。MATLAB求解器也被用來求解Poisson方程的Neumann邊界條件問題，最終獲得了速度勢與拍翼流場的流線圖。

關鍵字

拍翼 ； 二維流場 ； 泡膜 ； PVDF

並列摘要

This thesis presents a 2D quasi-steady flow simulation of a 10 cm wingspan flapping wing with given moving boundary fed from stereo-photography measurement. This trajectory work used the softwares Surfer and Gambit to slice a 2D quarter-span cross section from the 3D trajectory by stereo photography. It’s then regarded as a 2D moving boundary for the quasi-steady CFD simulation by ANSYS/Fluent. The upwind direction changing of the flapping flow field has also been novelly considered herein. The computed time-varying outputs include the 2D flow fields and the corresponding lift coefficient. The one cycle history of lift coefficient subjected to 40 Hz flapping shows the qualitative similarity to the corresponding wind tunnel data and PVDF on-site measurement data.
A novel method utilizing bubble film to observe the flapping flow field has been also developed and tested in this thesis. This work is based on the concept of thin film interference where bubble film of different thickness exhibits different chromatic appearance. Herein, the bubble film was subjected to the flow field of a 10 cm wingspan flapping wing, and a color CCD camera was used to capture the chromatic patterns on the bubble film. The captured photograph was fed into MATLAB to generate RGB values per pixel and corresponding thickness values based on the standard color card for bubble thickness. The commercial finite difference solver in MATLAB was also used to solve the Neumann boundary value problem of Poisson equation to obtain the velocity potential field and the corresponding stream line pattern of the flapping flow field. Some technical difficulties were addressed finally.

並列關鍵字

flapping ； two-dimensional flow field ； bubble films ； PVDF

參考文獻

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