Examples of biomimetic flow controls: (a) sketch of flying machine by Leonardo da Vinci (Biblioteca Ambrosiana, Milan); (b) Mercedes-Benz bionic car (photograph courtesy of Daimler AG).
Alula and its aerodynamic characteristics: (a) alula on the bird wing; (b) lift-to-drag ratio with the angle of attack (α) at Re c = 2.6 × 104 (left) and 9.5 × 104 (right) (○, without alula; •, with alula); (c) flow visualization in the wake behind a magpie wing with (left) and without (right) alula at α = 25° and Re c = 2.6 × 104.
Leading-edge serrations and tubercles: (a) combed serrations on the leading edge of the owl feather (photograph courtesy of A. Sieradzki); (b) picture of the pantograph (Shinkansen 500 series) with vortex generators mimicking owl's serrations (photograph Shinkansen courtesy of Kanazawa Yuzi); (c) humpback whale (Megaptera novaeangliae) flipper - leading edge tubercles (photograph courtesy of William Rossiter).
Hindwing tails of the swallowtail butterfly: (a) planform shape of the swallowtail butterfly (Graphium policenes policenes) in gliding flight; (b) variations of the lift (C L ), drag (C D ), and pitching moment (C M ) coefficients with the angle of attack (α) at Rec = 14 400 (•, C L with tails; ○, C L without tails; ▲, C D with tails; Δ, C D without tails; ■, C M with tails; □, C M without tails). Here, , L, D, and M are the lift and drag forces, and pitching moment, respectively, ρ is the density, and A is the wing planform area. Reprinted with permission from H. Park, K. Bae, B. Lee, W.-P. Jeon, and H. Choi, Exp. Mech. 50, 1313 (2010). Copyright 2010 Society for Experimental Mechanics.
Trailing edge of a dragonfly wing: (a) magnified view (photograph courtesy of Antonia Kesel 48 ); (b) spade-like protrusions on the trailing edge of an airfoil with a gurney flap. Reprinted with permission from W. Hage, AIAA Paper No. 2000-2315, 2000. Copyright 2000 American Institute of Aeronautics and Astronautics.
Aerodynamic effect of trailing-edge protrusions on a dragonfly wing in a hovering motion (Re U = 1900): 50 (a) rectangular protrusions on the trailing edge of a dragonfly forewing model; (b) definitions of the wing kinematic parameters and the force components on the wing; (c) temporal variations of the drag (C D ) and lift (C L ) force coefficients on the wing models with and without protrusions.
Secondary feather of a bird: (a) Skua wing in landing approach (photograph courtesy of Ingo Rechenberg); (b) real application to a glider plane. Reprinted with permission from M. Schatz, T. Knacke, F. Thiele, R. Meyer, W. Hage, and D. W. Bechert, AIAA Paper No. 2004-1243, 2004. Copyright 2004 American Institute of Aeronautics and Astronautics.
Corrugated surface of a dragonfly (Aeshna juncea) wing: (a) photograph of cross sections of the forewing of a dragonfly; 50 (b) streamlines near a corrugated wing at α = 10° in gliding motion. Reprinted with permission from H. Hu, J. Aircraft 45, 2068 (2008). Copyright 2008 American Institute of Aeronautics and Astronautics.
Effect of surface corrugations on the aerodynamic forces in a dragonfly-like inclined hovering motion: 50 (a) definitions of the wing kinematics and force components; (b) schematic diagrams of smooth and corrugated wing models, the width (w) and depth (h) of the corrugations are w/c = 0.15 and h/c = 0.045, where c is the mean chord length of the wing; (c) temporal variations of the drag (C D ), lift (C L ), vertical (C V ) ,and horizontal (C H ) force coefficients of the smooth and corrugated wing models.
Hydrodynamic effect of surface grooves on a scallop shell: (a) swimming sequence of a real scallop recorded by cine camera; (b) scallop model considered in the present study (Patinopecten yessoensis) and the shape of surface grooves on its upper and lower surfaces; (c) variation of the lift-to-drag ratio (L/D) with α ((red solid circle), with grooves; (blue open circle), without grooves). Figure 10(a) is reprinted with permission from B. Morton, J. Zool. London 190, 375 (1980). Copyright 1980 John Wiley and Sons.
Skin-friction variation of the V-grooved riblet surface with the tip-to-tip spacing (s + ): •, Sagong et al. 86 (experiment, h = 0.35 mm and s = 0.4 mm at Re θ = u ∞θ/v = 4400–8300, where θ is the momentum thickness); ■, Sagong et al. 86 (simulation, h + = s + = 10); ▼, Sagong et al. 86 (simulation, h + = 17 and s + = 20); ○, Walsh 81 (h = s = 0.25 mm); □, Walsh 81 (h = s = 0.51 mm); ∇, Bechert et al. 84 (h = 2.63 mm and s = 3.04 mm); Δ, Bechert et al. 84 (h = 5.28 mm and s = 6.1 mm). Reprinted with permission from W. Sagong, C. Kim, S. Choi, W.-P. Jeon, and H. Choi, Phys. Fluids 20, 101510 (2008). Copyright 2008 American Institute of Physics.
Shape and performance of sailfish skin: (a) skins of the sailfish; (b) schematic of the protrusions placed on a flat plate (parallel, staggered, and random distributions); (c) variations of skin friction with the width of protrusion (staggered distribution): ○, (H +, S z /W, S x /L) = (7.3, 2, 2); Δ, (8.1, 2, 2); □, (9.8, 2, 2); Δ, (11.7, 2, 2); ◊, (12.5, 2, 2); •, (6.1, 4, 2); ■, (9.8, 4, 2); ▼, (11.7, 4, 2); ♦, (12.5, 4, 2). Reprinted with permission from W. Sagong, C. Kim, S. Choi, W.-P. Jeon, and H. Choi, Phys. Fluids 20, 101510 (2008). Copyright 2008 American Institute of Physics.
Bursting and cruising speeds of fast sea animals.
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