| After million years of evolution, birds have excellent flight characteristics: birds withlarge wings can produce higher lift because of the large contact area between their wings andthe air, while the birds with long, narrow wings can carry out long-distance gliding becausethe large spanwise and shuttle-shape wings can reduce the air resistance to improve theflying efficiency. The excellent flight characteristics are decided by the feather structure andairfoil shape of the wings, especially the airfoil which is a key factor closely related to flightinefficiency. The research on bird airfoil has its important bionic meaning and applicationprospects, which provides a design inspiration for wind turbine blades, wings and other keycomponents in the aircraft.This thesis takes the barn swallows as an example, analysis the feather characteristic,and concludes the relationships between the feather structure and the flight characteristics. Inbarn swallows, feathers, rachis and pinna constitute a strong and flexible pinna, which canreduce the air resistance and increase the buoyancy of the bird’s body. On the other hand, thefeathers are hydrophobic and anisotropic, keeping the body clean from water and dirt. Thisproperty efficiently reduces the wind resistance and allows the bird to achieve rapid flight.This thesis presents a thorough kinematics analysis of the barn swallows, concludes twokinds of wing patterns when they are gliding: swept-shaped wings and fully expandedshaped wings. By using reverse engineering technology, interception of two wings patterns isperformed on airfoil in aspect ratio25%,30%,35%,40%,45%,50%, and gained the wingsection geometry parameter.Airfoil meshing is extracted using ICEM software, Numerical simulation on theaerodynamic characteristic using FLUENT software under the condition of using Reynoldsnumber of6×10~4、8×10~4, and attack angle of0~15°, results show that the airfoil at thefully expanded shaped wings aspect ratio of25%and swept-shaped wings aspect ratio of35%of the airfoil have the best aerodynamic characteristics. When the Reynolds numberreaches Re=6×10~4, Barn swallows fully expanded airfoil aspect ratio of25%is1.4times than the standard airfoil, Lift-drag ratio increased30%, Barn swallows Swept-shaped wingsaspect ratio of35%lift coefficient is1.2times and Lift-drag ratio increased48%than thestandard airfoil; When the Reynolds number reaches Re=8×10~4, Barn swallows fullyexpanded airfoil aspect ratio of25%is1.4times than the standard airfoil, Lift-drag ratioincreased30%, Barn swallows Swept-shaped wings aspect ratio of35%lift coefficient is1.03times and Lift-drag ratio increased48%than the standard airfoil; Analysis of Biologicalairfoil to improve the the mechanism of the aerodynamic performance showed that:(1) Thewing section has the small thickness and the leading edge radius, causes the wing sectionfrontal area to be small, the resistance is small;(2) The wing section static pressure curveforms the area to be big, the wing section has the big lifting force;(3) The maximumthickness of the airfoil near the trailing edge, which be able to delay the occurrence of stall,and ensure small energy loss, high efficiency.The representative and standard airfoil of the swallow airfoil are processed on theengraving machine, and their aerodynamic characteristics are tested in the small wind tunnel.Results show that the barn swallows in different wind speeds, fully expanded-shaped wingsin aspect ratio of25%and barn swallows swept-shaped wings in aspect ratio for35%of theairfoil provide the optimal aerodynamic characteristics. They pertain good adaptability underdifferent wind speed, which verified the correctness of the numerical simulation result. Theacquisition of these two excellent airfoils provides significant guidance for the future airfoilextraction. |
PDF Full Text Request