 | Gardner A.D. Investigations of dynamic stall and dynamic stall control on helicopter airfoils: kumulative Habilitationschrift zur Erlangung der Lehrbefugnis für das Fachgebiet Strömungsmechanik / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Aerodynamik und Strömungstechnik, Göttingen. - Köln: DLR, 2016. - 207 p.: ill., tab. - (Forschungsbericht; 2016-55). - Res. also Germ. - Bibliogr.: p.187-195. - ISSN 1434-8454
Шифр: (Pr 1120/2016-55) 02
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Abstract ........................................................ 5
Foreword ........................................................ 7
Acknowledgments ................................................. 9
Nomenclature ................................................... 11
1 Introduction .............................................. 17
1.1 Dynamic stall on a helicopter airfoil ..................... 22
1.2 Visualisation of dynamic stall in the literature .......... 29
1.3 Similarity parameters for dynamic stall ................... 35
1.4 Dynamic stall control in the literature ................... 36
1.5 Overview of topics in the cumulative habilitation thesis .. 46
2 Pitching airfoil experiments .............................. 53
2.1 Description of the experimental arrangement ............... 53
2.1.1 DNW-TWG with adaptive-wall test section ............ 53
2.1.2 Pitching motion test stand ......................... 54
2.1.3 Wind tunnel airfoil model .......................... 56
2.1.4 Pressure sensor positioning ........................ 58
2.1.5 Data analysis ...................................... 59
2.2 Dynamic stall results ..................................... 61
2.2.1 Experimental arrangement ........................... 61
2.2.2 Data averaging ..................................... 62
2.2.3 Variation of amplitude ............................. 64
2.2.4 Variation of frequency ............................. 68
2.2.5 Higher order pitching motion ....................... 71
2.2.6 Comparison of the airfoils ......................... 73
2.2.7 Damping-criterion .................................. 75
2.2.8 Conclusion ......................................... 78
3 3D effects on pitching airfoil experiments ................ 79
3.1 Effect of wall connection ................................. 80
3.2 Effect of finite wing length and rotation ................. 86
3.2.1 Computational approach ............................. 87
3.2.2 Non-rotating test case ............................. 90
3.2.3 Rotating test case ................................. 93
3.2.4 Discussion ......................................... 97
3.2.5 Conclusions ........................................ 99
3.3 3D flow on the model centerline .......................... 100
3.3.1 High speed PSP measurements ....................... 101
3.3.2 Dynamic stall at Mach 0.3 ......................... 104
3.3.3 Dynamic stall at Mach 0.5 ......................... 107
3.3.4 Conclusions ....................................... 110
4 Dynamic stall control by blowing ......................... 111
4.1 Design of constant blowing experiments using CFD ......... 113
4.1.1 The LEVoG experiments of Mai et al ................ 114
4.1.2 Definitions ....................................... 116
4.1.3 Computational approach ............................ 116
4.1.4 Deep dynamic stall on the OA209 ................... 118
4.1.5 The vertical slot and LEVoGs ...................... 120
4.1.6 RANS results at α=17.5° ........................... 121
4.1.7 URANS results with α=12.87±7.13° at CM=0.06 ....... 125
4.1.8 URANS results with α=12.87±7.13° at Сд=0.03 ....... 129
4.1.9 Estimate of the power required for actuation ...... 130
4.1.10 Conclusion ........................................ 130
4.2 Design of pulsed blowing experiments using CFD ........... 132
4.2.1 Grid and solver ................................... 132
4.2.2 The "pulsed injection" actuator boundary
condition ......................................... 133
4.2.3 Results ........................................... 134
4.2.4 Conclusion ........................................ 137
4.3 Results with constant blowing ............................ 138
4.3.1 Numerical method .................................. 139
4.3.2 Data analysis ..................................... 140
4.3.3 Results at static angle of attack ................. 144
4.3.4 Dynamic stall control at Mach 0.3 ................. 145
4.3.5 Investigation of optimum pressure and jet
spacing ........................................... 148
4.3.6 Dynamic stall control at Mach 0.4 ................. 151
4.3.7 Dynamic stall at Mach 0.5 ......................... 152
4.3.8 Stall control with constant blowing at Mach 0.5 ... 156
4.3.9 Optimization of blowing at Mach 0.5 ............... 160
4.3.10 Aerodynamic damping at Mach 0.5 ................... 163
4.3.11 Conclusions ....................................... 164
4.4 3D effect of flow control by blowing ..................... 166
4.4.1 Conclusions ....................................... 169
4.5 Results with pulsed blowing .............................. 170
4.5.1 Data analysis ..................................... 171
4.5.2 Results for pulsed blowing ........................ 173
4.5.3 Switching constant blowing at 1/rev ............... 178
4.5.4 Conclusions ....................................... 181
5 Conclusions .............................................. 183
Bibliography .................................................. 187
Vita .......................................................... 197
List of publications .......................................... 199
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