翼尖小翼對風車葉片流場及空氣動力噪音之影響探討

A Study of the Effects of a Winglet on the Flow Field and Aeroacoustics for Wind Turbine Blades

張雅茹(Ya-Ju Chang)

指導教授 ： 王昭男

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.00387

摘要

本文主要在探討氣流流經風車葉片時，增加翼尖小翼前後與改變翼尖小翼幾何特徵，對於翼尖渦漩流場與聲場所造成的影響。文中使用有限體積法離散控制方程式，之後以分離式求解法，逐一求解各變量的代數方程組，並採用雷諾平均法(RANS)配合Realizable 紊流模式求解紊流流場。為了確保分析的準確性，必須先針對所使用軟體進行驗證，確認紊流流場計算的可靠度。首先針對穩態均勻流通過二維與三維翼型進行驗證，探討氣流流經翼型時的升力與阻力係數，計算其流場氣動力性能，並針對矩形翼渦心軌跡作追蹤，同時與實驗數據比較，確認本文方法的可靠性，爾後方能據以此步驟分析矩形翼增加翼尖小翼前後與改變翼尖小翼特徵對於翼尖渦漩之影響探討。

在進行三維矩形翼模擬之前，文中先針對NACA-64(3)-618與NACA-0012翼型進行二維與三維模擬，同時與實驗數據驗證，結果顯示，升力係數與實驗數據接近，而阻力係數呈現稍大現象；並進而追蹤NACA-0012矩形翼渦心軌跡位置，整體渦心發展方向與實驗值比較趨勢接近。爾後，便以此模式為基礎，進行三維NACA-64(3)-618矩形翼之翼尖渦漩流場與聲場探討。

本文在聲場分析中，採用以Lighthill 聲學類比理論為基礎之寬頻帶噪音模式(Broadband Noise Source Model, BNS)，並使用Proudman方程式計算每單位體積聲音輸出功率。文中僅以翼尖渦漩產生之噪音總量作為比較的指標，分析增加翼尖小翼前後與改變翼尖小翼特徵(漸縮比、傾斜角、長度)，在不同入流速度與不同入流攻角的情形下，探討翼尖渦漩的氣動性能與空氣動力噪音所造成的影響，以期找出減噪效果較佳的翼尖小翼。結果顯示，風車葉片加裝翼尖小翼後可提升氣動性能，而本文所研究減噪效果最佳之翼尖小翼，翼尖渦漩之聲功率位準可降低約5.4dB，期望此研究可作為將來風車葉片設計的參考依據。

關鍵字

翼尖小翼 ； 翼尖渦漩 ； 有限體積法 ； 雷諾平均法 ； 寬頻帶噪音模式

並列摘要

The purpose of this research is to investigate the effects of a winglet on the flow field and aeroacoustics of a three dimensional wing. The SIMPLE algorithm based on finite volume method was used in this numerical analysis. For simplicity, Reynolds Averaged Navier-Stokes equations combined with Realizable turbulent model are used to solve the turbulent flow. Since the aerodynamic noise of tip vortex is induced by the turbulent flow, the flow field analysis and verification are required. First, the uniform flow past a two-dimensional airfoil and a three-dimensional wing are analyzed, in order to establish the accuracy of the simulations and understand the effects of flow induced noise on the performance of the rectangular wing. Also, tracking of the tip vortex of a rectangular wing is evaluated. The agreement between the simulated results and experimental datum is good. Therefore, all of the analyses in this study are based upon this meshing model. For the sound field analysis, the flow induced noise around a rectangular wing is computed by the Broadband Noise Source (BNS) model. Proudman’s formula was used to evaluate acoustic power per unit volume of aerodynamic noise. The study focuses on the sound power of aerodynamic noise generated by tip vortex when the flow passes through a wing and a wing with winglet. In order to understand the effects of the winglet on the aerodynamic noise, the different winglet characteristics, such as taper ratio, cant angle, and winglet length are investigated and discussed. It is found that with a winglet the dynamic coefficient is improved and the generated sound power is also reduced by about 5.4 dB. It is hoped that this study will have some contributions to the wind turbine industry.

並列關鍵字

aerodynamic noise ； turbulent ； tip vortex ； winglet ； BNS

參考文獻

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