隨著全世界科技的進步，人口的上升，能源耗盡成為我們重視的議題。因此取之不盡用之不竭的再生能源成為大家近期所研究的對象，其中風力發電是一種不錯的再生能源。風力發電可分為水平式與垂直式兩種風力機，吾人在此研究中所探討的是單片翼型為NACA4412之葉片的垂直式風力機進行模擬。進而加裝Gurney flap，進行探討加裝置在模擬過後的氣動力分析是否能改善其葉片轉動的效能。在數值分析中，使用二階精確浸入邊界法來了解Gurney如何影響升力垂直軸風力發電機。我們模擬測試使用流速為U = 1 m / s的流場條件。假設十萬雷諾數的情況下，在紊流中選擇人工可壓縮法來求解不可壓縮的Navier-Stokes方程。

With the growth of economy and development of industry throughout the world, the energy consumption is great needs. Instead of traditional fossil fuels, the renewable energy has gradually attracted in practical applications or academic studies. One of the widely used renewable energy is the wind. In this study, the aerodynamic characteristics of a vertical-axis wind turbine installing with high-lift devices, such as the Gurney flap at the trailing edge is  investigated. In numerical analysis, second-order accurate immersed boundary method is used to understand how the Gurney flap influences the force decomposition of the lift vertical-axis wind turbine. The test cases use the flow conditions of the incoming flow velocity as U =1 m/s. The artificial compressibility is chosen in the evaluation of turbulence effects in solving the incompressible Navier-Stokes equations under the assumption of one millions of Reynolds number.

Chapter 1 Introduction	1
1.1 Background	1
1.2 Literature Review	2
1.3 Purpose of the Study	6
Chapter 2 Numerical Modeling	7
2.1 Governing Equations	7
2.2 Numerical Validation	10
Chapter 3 Results and Discussions	12
3.1 Original Case ( pure single airfoil )	12
3.2 Addition with Gurney	19
3.2.1 Rotational frequency k=1	19
3.2.2 Rotational frequency k=0.5	24
3.2.3 Rotational frequency k=0.1	28
3.3 Addition with Gurney & Cover	33
3.4 Addition with Gurney for three airfoils	45
3.4.1 Comparison the force component for the different rotational frequencies of the three airfoils	46
3.4.2 Analysis of the three airfoil aerodynamic characteristics using the force-element theory	49
3.4.3 Comparison of the single airfoil and the three airfoils	52
Chapter 4 Conclusions	54
Reference	55

 
Figure Contents
Figure 1 Vorticity contours of the flow around a cylinder at Re=150	11
Figure 2 Illustration of the single airfoil in the vertical axis wind turbine	12
Figure 3 Contour plots of the vorticity for the single airfoil in one rotation.	15
Figure 4 Components of force for the single airfoil	17
Figure 5 Illustration of the single airfoil addition with Gurney	19
Figure 6 Contour plots of the vorticity for the single airfoil with Gurney k=1 in one rotation	20
Figure 7 The force component for the single airfoil with Gurney k=1 (a) CL (b) CD and (c) CM respectively.	22
Figure 8 Contour plots of the vorticity for the single airfoil with Gurney k=0.5 in one rotation	25
Figure 9 The force component for the single airfoil with Gurney k=0.5 (a) CL (b) CD and (c) CM respectively.	27
Figure 10 Contour plots of the vorticity for the single airfoil with Gurney k=0.1 in one rotation	30
Figure 11 Components of force for the single airfoil with Gurney	31
Figure 12 Illustration of the single airfoil addition with Gurney & cover in the vertical axis wind turbine	33
Figure 13Contour plots of the vorticity for the single airfoil with Gurney and cover	35
Figure 14 Components of force for the single airfoil with Gurney and cover	38
Figure 15 Comparison of  lift coefficient for 3 case (case1: single airfoil, case2: single airfoil+Gurney, case3: single airfoil+Gurney+cover)	39
Figure 16 Comparison of drag coefficient for 3 case (case1: single airfoil, case2: single airfoil+Gurney, case3: single airfoil+Gurney+cover)	40
Figure 17 Comparison of moment coefficient for 3 case (case1: single airfoil, case2: single airfoil+Gurney, case3: single airfoil+Gurney+cover)	41
Figure 18 Comparison of lift coefficient to reduced frequency for the single airfoil	42
Figure 19 Comparison of drag coefficient to reduced frequency for the single airfoil	43
Figure 20 Comparison of moment coefficient to reduced frequency for the single airfoil	44
Figure 21 Illustration of the three airfoils addition with Gurney in the vertical axis wind	45
turbine	45
Figure 22 The force decomposition for the different rotational frequencies	48
Figure 23 Comparison of lift coefficient to single airfoil and three airfoils	52
Figure 24 Comparison of drag coefficient to single airfoil and three airfoils	53
Figure 25 Comparison of moment coefficient to single airfoil and three airfoils	53



 
Table Contents
Table I The Comparison of the Numerical and Experimental Strouhal Number	11
Table II Contributions to the force coefficient by the force component during a periodical cycle for a vertical axis wind with pure airfoils	18
Table III Contributions to the force coefficient by the force component during a periodical cycle for a vertical axis wind with pure airfoils	23
Table IV Contributions to the force coefficient by the force component during a periodical cycle for a vertical axis wind with pure airfoils	28
Table V Contributions to the force coefficient by the force component during a periodical cycle for a vertical axis wind with pure airfoils	32
Table V Contributions to the force coefficient by the force component during a periodical	38
cycle for a vertical axis wind with pure airfoils	38
Table VI Contributions to the lift coefficient by the lift elements during a periodical cycle for a vertical axis wind with a Gurney flap	50
Table VII Contributions to the drag coefficient by the drag elements during a periodical cycle for a vertical axis wind with a Gurney flap	51

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