摘要
本文主要在探討氣流流經二維風車翼面時，氣流場壓力變動所產生的噪音，文中選取六種風車葉片類型進行分析，探討不同的翼型、入流速度、入流角度等因素對噪音產生之影響。文中將計算域以C 型結構劃分網格，同時符合壁函數之設計範圍。本文採用有限體積法來離散控制方程式，離散後的代數方程式以分離求解法，逐一的求解每ㄧ個方程式，利用疊代方式求解。控制方程式係採用雷諾 平均方程式（RANS），再配合k-e紊流模式來計算雷諾應力分佈，求解紊流流場，驗證其二維翼型升力係數、阻力係數及壓力係數，藉此可得到正確的紊流場資訊，方能據以分析此紊流場所產生之噪音量。為累積分析經驗，首先以簡單之對稱翼型NACA0012 作為分析對象，藉此確認較佳的網格劃分方式與數量，爾後再針對 其他翼型（NACA0015、DU95-W-180、NACA64(3)-218、S822與S809）進行動力係數的分析，同時與實驗數據比對，以驗證分析的正確性。結果顯示，升力係數相當一致，阻力係數方面本文之分析結果略為偏大，整體而言尚在可接受的範圍，之後，即以此為基礎，進行紊流噪音分析。在聲場分析中，文中採用寬頻帶噪音模式（Broadband Noise Source Model, BNS）進行計算，並以Lighthill 之聲學類比為基礎，使用Curle 方程式進行表面聲功率位準（Surface Acoustic Power level,SAPL）的預測，分析二維風車葉片在不同風速與入流攻角的情形下，紊流在翼型表面所產生的噪音量，藉由表面聲功率位準歸納其風機性能佳且噪音值小之風機外型，以期能減少風力發電機對環境之衝擊，提升風力發電之產能。
並列摘要
The purpose of this research is to investigate the two dimensional wind turbine blade noise which is induced by the pressure variation in the turbulent flow. In this study, six airfoils are chosen to investigate. The influences of type of airfoil, flow velocity and angle of attack on the turbulence noise generation have been discussed. Firstly, the computational domain is meshed by the C type structure and the mesh satisfies the requirement of wall function that is used near the boundary surface. Reynolds averaged Navier-Stokes (RANS) equations are used to describe the turbulent flow field and the Reynolds stresses are calculated through the k-e model. The SIMPLE algorithm with finite volume based scheme was used in this numerical analysis. Then the flow field around a two dimensional airfoil is analyzed and the lift, drag and pressure coefficients are used as the parameters to verify the accuracy of the present numerical approach. The symmetric airfoil NACA0012 is analyzed firstly in order to test the mesh distribution and required mesh number that can provide enough accuracy. Then the other five airfoils, NACA0015, DU95-W-180, NACA64(3)-218, S822 and S809 are also analyzed. The agreement between the numerical results of aerodynamic coefficients and the experimental measurements are good except for the drag coefficient has larger discrepancy. Then the turbulent flow noise is analyzed based on this flow field analysis. For the sound field analysis, the turbulence induced sound power is evaluated by Broadband Noise Source (BNS) model, namely Curle’s boundary layer model for dipole source. This model is an extension of the Lighthill’s general theory of aerodynamic sound, so as to incorporate the influence of solid boundaries. This equation requires the data of the flow field as input. In this work, the Curle’s formulation built in Fluent is adopted to analyze the surface acoustic power level (SAPL) of flow pass through an airfoil. Hoping that the lower noise airfoils can be selected and the impact of the wind turbine on the environment can be reduced.