Aerodynamics and Design for Ultra-Low Reynolds Number Flight

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Chapter 5 82 FIGURE 5.6 Small test fixture in the large torque testing configuration. The ability to measure rotor torque with this setup is limited by the maximum precision of the electronic balance and physical constraints that limit the minimum length of the moment arm. The micro-rotors are under three centimeters in diameter and generate roughly 100 µNm of torque. At these low magnitudes, factors such as bearing stiction and the dynamics of the load cell come into play, making accurate and repeatable measurement difficult. Another test configuration has been developed to address the majority of these issues. This approach uses the mounting bracket of the balance arm as a simple fulcrum balance. After leveling the bracket, mass is added to one side and the rotor is spun up until it supports the added mass. The mount is machined with precisely located threaded holes providing both a known offset and a secure means of attachment for the added mass.
Chapter 5 The direct influence of the scale is removed since it is only used to measure the added mass prior to the experiment. Bearing stiction errors are reduced by lightly perturbing the system once balanced to assure it returns to equilibrium. Finally, the resolution is greatly increased by reducing the moment arm from 0.73” to 0.25”. This revised test fixture is pictured in Figure 5.7. FIGURE 5.7 Small test fixture configured for small torque measurements. The evaluation of motor performance is accomplished by coupling the shafts of two motors. The test motor is mounted to the stand in the same manner as for large magnitude torque testing. A second motor acts as a torque load and is mounted in a second fixture such that the drive shafts are co-linear. The test motor is powered by a constant voltage power supply. Torque, RPM, and current data are recorded as the load torque is gradually increased until the rated stall current is achieved. From this data, 83
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AERODYNAMICS AND DESIGN FOR ULTRA-L
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I certify that I have read this dis
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Abstract Growing interest in micro-
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Nomenclature A Rotor disk area B Nu
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τ Shear stress ω, Ω Rotor angul
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Contents Acknowledgments...........
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Chapter 5..........................
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List of Tables 3.1 Effect of Airfoi
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List of Figures 2.1 Comparison of I
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5.6 Small test fixture in the large
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6.38 Predicted spanwise thrust dist
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Chapter 1 Introduction 1.1 Looking
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Chapter 1 wind-tunnel facilities an
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1.3 Summary of Contributions Chapte
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Chapter 2 Two-Dimensional Computati
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Chapter 2 The artificial compressib
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Chapter 2 The control volume method
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2.2.4 Comparison with Experiment Th
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Chapter 2 to diverge if significant
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2.4 Flow Field Assumptions The INS2
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Chapter 2 The results of these time
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Chapter 3 Analysis and Design of Ai
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Chapter 3 adverse gradient in the p
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The canonical pressure coefficient
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Chapter 3 reaches α=5.0 and a lift
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��
Page 55 and 56: Cl 0.50 0.40 0.30 0.20 0.10 0.00 -0
Page 57 and 58: Re=6000 result due to Reynolds numb
Page 59 and 60: FIGURE 3.10 NACA 0002 and NACA 0008
Page 61 and 62: C l C l 0.8 0.7 0.6 0.5 0.4 0.3 0.2
Page 63 and 64: Chapter 3 The maximum L/D for all n
Page 65 and 66: 3.5 Effect of Leading Edge Shape an
Page 67 and 68: C l 0.60 0.50 0.40 0.30 0.20 0.10 0
Page 69 and 70: Chapter 3 prominent droop near the
Page 71 and 72: Chapter 3 Small improvements in lif
Page 73 and 74: Chapter 4 Hybrid Method for Rotor D
Page 75 and 76: Q/r D L Chapter 4 FIGURE 4.1 Typica
Page 77 and 78: 4.2.3 Elimination of Trigonometric
Page 79 and 80: Chapter 4 applications of interest
Page 81 and 82: 4.2.7 The Distinction Between the A
Page 83 and 84: Chapter 4 Two input parameters dete
Page 85 and 86: Chapter 4 simplification, particula
Page 87 and 88: 4.3.3 Conservation of Angular Momen
Page 89 and 90: Chapter 4 moves downstream is less
Page 91 and 92: Chapter 4 of the pitch angle at the
Page 93 and 94: FIGURE 4.6 Converged wake streamlin
Page 95 and 96: Chapter 4 idealized models. The met
Page 97 and 98: ��
Page 99 and 100: Chapter 5 Overview of Experimental
Page 101 and 102: 1. Substrate Preparation 2. Polymer
Page 103 and 104: Chapter 5 surface finish and aids i
Page 105: FIGURE 5.5 Small test fixture in th
Page 109 and 110: FIGURE 5.9 Large test fixture in th
Page 111 and 112: 5.4.1 Motor Power Supply All tests
Page 113 and 114: Chapter 5 or roughly (+/-) 25% of t
Page 115 and 116: Chapter 5 newly forming blade tip v
Page 117 and 118: FIGURE 5.14 Near-body grid geometry
Page 119 and 120: Chapter 6 Design Examples and Compa
Page 121 and 122: Chapter 6 capable of speeds up to 1
Page 123 and 124: FIGURE 6.2 The Astro Flight Firefly
Page 125 and 126: t/c 0.5 0.4 0.3 0.2 0.1 0.0 FIGURE
Page 127 and 128: c/R 0.0 0.2 0.4 0.6 0.8 1.0 r/R Cha
Page 129 and 130: FIGURE 6.10 Carbon-fiber two-blade
Page 131 and 132: Power Req. (W) 3.5 3.0 2.5 2.0 1.5
Page 133 and 134: Chapter 6 TABLE 6.1 Comparison of p
Page 135 and 136: Electro-mechanical Efficiency 0.20
Page 137 and 138: these variations and possible solut
Page 139 and 140: upper and lower surface corners of
Page 141 and 142: Chapter 6 The Sample-1 rotor exhibi
Page 143 and 144: The static deformations described i
Page 145 and 146: Q( r) This problem is solved as a l
Page 147 and 148: Structural Analyses Chapter 6 The m
Page 149 and 150: Aero-Structural Twist (deg.) 0.00 -
Page 151 and 152: Thrust (g) 5 4 3 2 1 0 10000 20000
Page 153 and 154: Thrust (g) 4.5 4.0 3.5 3.0 2.5 2.0
Page 155 and 156: Torque per unit span (g cm) 0.75 0.
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Thrust per unit span (g) 3.5 3.0 2.
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V total / ωr 1.0 0.9 0.8 Classical
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Torque per unit span (g cm) 0.75 0.
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Chapter 6 Recall that this rotor wa
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Incidence (deg.) 30 25 20 15 10 5 0
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Thrust (g) 9 8 7 6 5 4 3 2 38000 40
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x/R 0.4 0.2 0.0 -0.2 Chapter 6 FIGU
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Cl 0.64 0.62 0.60 0.58 0.0 0.2 0.4
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C f 0.125 0.100 0.075 0.050 0.025 0
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Chapter 7 Micro-Rotorcraft Prototyp
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This vehicle does not currently inc
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FIGURE 7.2 The 65g prototype electr
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7.4 The 150g Prototype Chapter 7 Th
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At hover, with a mass of 153g, the
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Using the 150g prototype as an exam
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Chapter 7 Basic rotor theory has be
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most of the blade. These values are
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Chapter 7 For large scale helicopte
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Chapter 8 Conclusions and Recommend
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the significant performance gains a
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Chapter 8 are also opportunities to
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Chapter 8 formation flight, and man
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References [1] Spedding, G.R., Liss
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[28] Lamb, Sir Horace, Hydrodynamic
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Aerodynamics and Design for Ultra-Low Reynolds Number Flight

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