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<p>Recent studies have claimed that bioinspired corrugated airfoils outperform conventional airfoils in terms of aerodynamic performance at ultralow Reynolds flow regimes. This study focused on optimizing the shape of a corrugated airfoil inspired by the cross-section of a dragonfly wing under different flight conditions at Reynolds numbers (<i>Re</i>) of 1000 and 10000. The first objective was to maximize the lift-to-drag ratio, which is critical for gliding as well as flapping during the downstroke of dragonfly wings. The second objective was to minimize drag at minimum lift, which is crucial during the upstroke phase of flapping flight. The optimization process was performed using a genetic algorithm via MATLAB’s “ga” function, which was integrated with the Fluent software to solve two-dimensional, laminar, incompressible Navier–Stokes equations. The upper surface points of the corrugated airfoil were used as the initial 17 geometrical variables with constraints imposed to maintain the plate thickness and to fix the leading and trailing edges. The results of the first optimization demonstrated that the zigzag pattern of the corrugated airfoil was eliminated, and the shape converged to a cambered plate. As a result, the optimized cambered plate achieved lift-to-drag ratios of 5.65 at <i>Re</i> = 1000 and 12.23 at <i>Re</i> = 10000, representing 50 % and 96 % improvements over the original corrugated airfoil, respectively. This significant performance improvement rejected the superior aerodynamic performance of the bio-inspired corrugated airfoil for steady-state flight conditions at ultralow-<i>Re</i> flow regimes. The optimization process increased the lift coefficient significantly, and the overall drag coefficient only slightly increased. Notably, the pressure drag decreased, while the friction drag increased. The second optimization also eliminated the zigzag pattern, and the geometry converged to a flat plate. Generally, although the zigzag pattern reduced the friction drag due to the negative shear stress in the vortex region within the cavities, it increased the pressure drag. These findings offer a clearer understanding of how optimized geometries outperform traditional corrugated designs, under steady-state flight conditions at ultralow-<i>Re</i> flow regimes.</p>

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Shape optimization of a dragonfly-inspired corrugated airfoil in ultralow Reynolds flow regimes via a genetic algorithm

  • 期刊论文

  • 发表日期：

    2025年11月8日

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  • Mohammad Ali Forouzesh,
  • Mahdi Nili-Ahmadabadi,
  • Zakaria Drafsh,
  • Man Yeong Ha

摘要

Recent studies have claimed that bioinspired corrugated airfoils outperform conventional airfoils in terms of aerodynamic performance at ultralow Reynolds flow regimes. This study focused on optimizing the shape of a corrugated airfoil inspired by the cross-section of a dragonfly wing under different flight conditions at Reynolds numbers (Re) of 1000 and 10000. The first objective was to maximize the lift-to-drag ratio, which is critical for gliding as well as flapping during the downstroke of dragonfly wings. The second objective was to minimize drag at minimum lift, which is crucial during the upstroke phase of flapping flight. The optimization process was performed using a genetic algorithm via MATLAB’s “ga” function, which was integrated with the Fluent software to solve two-dimensional, laminar, incompressible Navier–Stokes equations. The upper surface points of the corrugated airfoil were used as the initial 17 geometrical variables with constraints imposed to maintain the plate thickness and to fix the leading and trailing edges. The results of the first optimization demonstrated that the zigzag pattern of the corrugated airfoil was eliminated, and the shape converged to a cambered plate. As a result, the optimized cambered plate achieved lift-to-drag ratios of 5.65 at Re = 1000 and 12.23 at Re = 10000, representing 50 % and 96 % improvements over the original corrugated airfoil, respectively. This significant performance improvement rejected the superior aerodynamic performance of the bio-inspired corrugated airfoil for steady-state flight conditions at ultralow-Re flow regimes. The optimization process increased the lift coefficient significantly, and the overall drag coefficient only slightly increased. Notably, the pressure drag decreased, while the friction drag increased. The second optimization also eliminated the zigzag pattern, and the geometry converged to a flat plate. Generally, although the zigzag pattern reduced the friction drag due to the negative shear stress in the vortex region within the cavities, it increased the pressure drag. These findings offer a clearer understanding of how optimized geometries outperform traditional corrugated designs, under steady-state flight conditions at ultralow-Re flow regimes.