While these issues may limit the applicability of blade-element type methods for detailed rotor design at ultra-low Reynolds numbers, such methods are still useful for evaluating concept feasibility and rapidly generating initial designs for prototyping and for further analysis and optimization using more advanced tools. Comparisons among the analyses and experimental data show reasonable agreement both in the global thrust and power, but the spanwise distributions of these quantities exhibit deviations, partially attributable to three-dimensional and rotational effects that effectively modify airfoil section performance. Performance predictions from these tools are compared with three-dimensional Navier-Stokes analyses and experimental data for several micro-rotor designs. This performance prediction method is coupled with optimization for both design and analysis. Building on these results, tools are developed for ultra-low Reynolds number rotors combining enhanced classical rotor theory with airfoil data from Navier-Stokes calculations. To further explore this design space, the flow solver has been coupled with an optimizer, resulting in the first airfoils quantitatively designed for this flow regime and demonstrating that unconventional camberlines can offer significant performance gains. Contrary to the notion that viscous fairing reduces airfoil geometry effectiveness, the computational results indicate that geometry still has a profound effect on performance at ultra-low Reynolds numbers. This performance penalty can be mitigated by careful airfoil design. Results indicate an increase in maximum lift coefficient with decreasing Reynolds number, but the lift to drag ratio continues to decrease, making the power required for flight a more restrictive consideration than lift. Variations in thickness, camber, and the shape of leading and trailing edges are studied. The effects of airfoil geometry on performance are explored using an incompressible Navier-Stokes solver. A reasonable starting point is the study of airfoil aerodynamics at Reynolds numbers below 10,000, here termed ultra-low Reynolds numbers. Two distinct types of hysteresis in reattachment were observed.Growing interest in micro-air-vehicles has created the need for improved understanding of the relevant aerodynamics. Once the flow was separated, the separation point moved upstream and the suction peak decreased in magnitude with increasing Reynolds number. The stall angle and the maximum lift coefficient increased with Reynolds number. As the Reynolds number was increased beyond this value, the stall type gradually shifted from trailing-edge stall to leading-edge stall. A fundamental change in the flow behaviour was observed around Re_c= 2.0 × 10^6. As such, attached and separated conditions, as well as the static stall and reattachment processes were studied. The angle of attack was incrementally increased and decreased over a range of 0° ≤ alpha ≤ 40°, spanning both the attached and stalled regime at all Reynolds numbers. The use of a high-pressure wind tunnel allowed for variation of the chord Reynolds number over a range of 5.0 × 10^5 ≤ Re_c ≤ 7.9 × 10^6. Reynolds number effects on the aerodynamics of the moderately thick NACA 0021 airfoil were experimentally studied by means of surface-pressure measurements. National Defense Science and Engineering Graduate Fellowship National Science Foundation grant CBET 1652583 Static measurements of a NACA 0021 airfoil at high Reynolds numbers Please use this identifier to cite or link to this item: Princeton University Undergraduate Senior Theses, 1924-2023 Princeton University Masters Theses, 2022-2023 Princeton University Doctoral Dissertations, 2011-2023 Princeton School of Public and International Affairs Liechtenstein Institute on Self-Determination Lewis-Sigler Institute for Integrative Genomics Department of Slavic Languages and Literatures
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