Numerical analysis of the effects of flexibility, shapes and aspect ratios on hovering wing aerodynamics

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Copyright: Shahzad, Aamer
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Abstract
Biological flight has inspired the development of micro aerial vehicles but the effects of flexibility, shapes and aspect ratios (AR) on hovering wing aerodynamics are still not fully understood. Here, the aerodynamic performance of a hovering wing with three shapes, defined by the radius of the first moment of wing area, r1 (= 0.43, 0.53 and 0.63), and four AR (= 1.5, 2.96, 4.5 and 6.0) has been studied numerically using a 3-D Navier-Stokes solver coupled with a structure solver. The performance trends of rigid wings at the Reynolds number (Re) of 12, 400 and 13500 have been observed to be independent of Re, because high suction pressures associated with the leading edge vortex are predominantly spread towards the tip and the trailing edge at all Re. Isotropic homogeneous flexible wings are modeled with a rigid leading edge at Re of 400. Although the lift is maximized using high (r1) and AR wings, low r1 and high AR (rigid and isotropic flexible wings at high mass ratio, m* = 4.0) are best for maximizing power economy (PE) for a given lift because small proportion of the wing area close to the distal region results in less aerodynamic power. However, at low m* = 0.66, there is a limited range of lift for which low r1 and high AR wings are efficient. Except for AR = 1.5, isotropic flexible wings have higher PE than rigid wings for all shapes. The effect of anisotropic flexibility on the performance is investigated by mapping the stiffness distribution of hawkmoth wing on all shapes at Re of 400. For a given shape, all anisotropic flexible wings generally produce more lift than rigid wings (except r1 = 0.53 and 0.63 at AR = 6.0) due to strong leading edge vortex resulting from combined chordwise-spanwise deformation, but not higher PE. Results here show that PE is maximized for hovering hawkmoth wings. Maximum PE for rigid, isotropic or anisotropic flexible wings is typically achieved at AR = 2.96, as low AR wing does not produce enough lift and high AR wings consume more aerodynamic power.
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Author(s)
Shahzad, Aamer
Supervisor(s)
Lai, Joseph
Tian, Fangbao
Young, John
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Publication Year
2018
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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