The desire and demand to fly farther and faster has progressively integrated the concept of optimization with airfoil design resulting in increasingly complex numerical tools pursuing efficiency often at diminishing returns, while the costs and difficulty associated with fabrication increases with design complexity. This paper establishes a method utilizing numerical tools for unoptimized design, focused on reducing the complexity of airfoils for applications where aerodynamic performance is less important than the efficiency of manufacturing. We applied this method to the development of a low Re, disposable Hybrid Projectile requiring a 4.5:1 glide ratio, resulting in a series of airfoils which are geometric approximations to highly contoured cross-sections called ShopFoils. This series of airfoils both numerically and experimentally perform within a 10% marigin of the SD6060 at low Re while reducing manufacturing costs and meeting the requirements of the HP platform.
A detailed computational investigation of the effects of aspect ratio and taper ratio on wings using the NACA 0009 airfoil operating at 30 m/s and a wing area of 0.01 m 2 was conducted. This required the construction of an extremely flexible geometry and mesh structure model and the preliminary validation of a steady-state turbulence model for low Reynolds number wings to complete the large parameter study required. The point of transition between low aspect ratio vortex lift and high aspect ratio circulation lift and the point of diminishing efficiency return on increasingly large aspect ratios are proposed. It is suggested that current high maneuverability MAV designs would not benefit from significant planform changes, but significant endurance and cruise efficiency benefits can be gained from higher aspect ratio designs. In addition, a preliminary model for the estimation of planform efficiency at low Reynolds numbers for low aspect ratio trapezoidal wings is proposed. An initial investigation into the formation of leading edge vortices and boundary layer recirculation bubbles is also performed. Nomenclature AR= aspect ratio c MAC = mean aerodynamic chord C L = three dimensional planform lift coefficient C l = two dimensional lift coefficient C Lα = derivative of three dimensional lift coefficient with respect to angle of attack C D = planform drag coefficient C d = two dimensional drag coefficient C D0 = three dimensional planform drag coefficient at zero lift PEF = planform efficiency factor Re = Reynolds number k n = constant of index n S W = wing area V ∞ = free stream velocity k n = constant of index n α = angle of attack λ = taper ratio
The desire and demand to fly farther and faster has progressively integrated the concept of optimization with airfoil design, resulting in increasingly complex numerical tools pursuing efficiency often at diminishing returns; while the costs and difficulty associated with fabrication increases with design complexity. Such efficiencies may often be necessary due to the power density limitations of certain aircraft such as small unmanned aerial vehicles (UAVs) and micro air vehicles (MAVs). This research, however, focuses on reducing the complexity of airfoils for applications where aerodynamic performance is less important than the efficiency of manufacturing; in this case a Hybrid Projectile. By employing faceted sections to approximate traditional contoured wing sections it may be possible to expedite manufacturing and reduce costs. We applied this method to the development of a low Reynolds number, disposable Hybrid Projectile requiring a 4.5:1 glide ratio, resulting in a series of airfoils which are geometric approximations to highly contoured cross-sections called ShopFoils. This series of airfoils both numerically and experimentally perform within a 10% margin of the SD6060 airfoil at low Re. Additionally, flow visualization has been conducted to qualitatively determine what mechanisms, if any, are responsible for the similarity in performance between the faceted ShopFoil sections and the SD6060. The data obtained by these experiments did not conclusively reveal how the faceted surfaces may influence low Re flow but did indicate that the ShopFoils did not maintain flow attachment at higher angles of attack than the SD6060. Two reasons are provided for the unexpected performance of the ShopFoil: one is related to downwash effects, which are suspected of placing the outer portion of the span at an effective angle of attack where the ShopFoils outperform the SD6060; the other is the influence of the tip vortex on separation near the wing tips, which possibly provides a 'comparative advantage' to the ShopFoil because it has more to gain from a reduction in its pressure drag component. Additionally, I appreciative of Dr. Loth for cultivating my conceptual understanding of fluid dynamics and thermodynamics as well as providing academic advice. Further, my thanks to Shanti Hamburg and Chris Menchini for offering guidance in developing my skills and understanding of Meshing and CFD. I appreciate the assistance from Dr. Xingbo Liu and Dr. Koorosh Mirfakhraie for recommending me to the WVU graduate engineering program. Thanks to Brian Parker for helping with my wind tunnel test preparations. To all of the influences throughout my life which gave rise to my interest in aeronautics, spaceflight, and the sciences.
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