中文摘要
題目: 在不同葉尖速比下模擬小型水平軸風機尾流特性驗證
學生: 方經緯
指導教授: 吳毓庭
此研究使用商用軟體ANSYS FLUENT針對本實驗室成員，許所設計的水平軸三葉縮尺風機葉片，葉片基於NACA 0012與葉片元素理論進行最佳化設計已達到良好的功率係數。風機葉片置放在成大工科再生能源實驗室中小型紊流風洞內(在輪轂高度的來流風速為6.1m s^(-1)、紊流強度為5%)來做尾流量測實驗。基於實驗所量測的邊界條件進行數值模擬分析，透由分析尾流的平均主流速度、紊流強度、主流紊流強度、動量通量等氣動力特性與實驗結果進行驗證。 在此模擬中，我們使用了大渦模擬求解暫態Navier-Stokes方程式與濾波後的亞格子模型(Smagorinsky-Lilly)。 在速度壓力耦合求解的部分使用SIMPLE 算法進行計算過程中,速度與壓力的佚代(iterate)。在速度邊界條件上，結合了Vortex Method (VM)演算法作為紊流產生器，使得下游風機在輪轂高度能接受符合實驗結果的紊流強度。　在實驗中，許使用了不同的葉尖速比來進行尾流風機的量測，其中葉尖速比的變因為透由改變電阻大小產生不同的轉速。因此，我們使用不同轉速做此為此模擬的主要變因，進行尾流特性分析。 在結果顯示出，隨著葉尖速比的增加，對尾流特性有顯著的影響。在特定的葉尖速比下，將產生大幅度的速度降與較高紊流強度。

關鍵字 : 水平軸風機、風機尾流、大渦模擬、渦旋法

ABSTRACT

Subject: Simulation of wake characteristics of horizontal axis miniature wind turbine operating different tip speed ratios

Student: Jing-Wei Fang

Advisor: Yu-Ting Wu

This study used the commercial software ANSYS FLUENT 17 simulated a horizontal-axis three-blade scale wind turbine which designed from our laboratory. The geometry of the blade was optimized based on NACA 0012 and blade element theory (BEM) to reach high aerodynamic performance. In the wind tunnel experiment, a miniature wind turbine rotor was operating with different angular velocities to measure its turbulence intensity at the downstream locations of a turbine. The aerodynamic characteristics of a turbine at the downstream locations x/d =1 to 8 such as time-averaged streamwise velocity, turbulence intensity, streamwise turbulence intensity, and momentum flux which are validated in this article. In this study, the viscous model was selected as Large Eddy Simulation model to resolve Navier-Stokes equations and filtered subgrid-scale model (Smagorinsky-Lilly) in the framework. The SIMPLE algorithm was used to calculate a discretization form of conservation equations and momentum equations. In configurations of velocity boundary conditions, Vortex Method (VM) algorithm was combined as a turbulence generator so that downstream wind turbine could get turbulence intensity from incoming flow approximately 0.05 measured in a wind tunnel experiment.

The boundary condition configurations have shown a specific aerodynamic behavior at the downstream of a turbine. While increasing angular velocity, the wind turbine wakes have different velocity deficit and turbulence intensity shown by contour plots. Comparison of profile plots has indicated distributions with different angular velocities along spanwise direction at hub height.

Keywords: Horizontal Axis Wind Turbine、Wind turbine wake、Large Eddy Simulation(LES) 、Vortex Method

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