Aerodynamics of Low Reynolds Number Flyers by Wei Shyy, Yongsheng Lian, Jian Tang, Dragos Viieru, Hao Liu

By Wei Shyy, Yongsheng Lian, Jian Tang, Dragos Viieru, Hao Liu

Low Reynolds quantity aerodynamics is necessary to a couple of normal and man-made flyers. Birds, bats, and bugs were of curiosity to biologists for years, and lively learn within the aerospace engineering group, inspired by means of curiosity in micro air automobiles (MAVs), has been expanding quickly. the first concentration of this publication is the aerodynamics linked to fastened and flapping wings. The publication ponder either organic flyers and MAVs, together with a precis of the scaling laws-which relate the aerodynamics and flight features to a flyer's sizing at the foundation of easy geometric and dynamics analyses, structural flexibility, laminar-turbulent transition, airfoil shapes, and unsteady flapping wing aerodynamics. The interaction among flapping kinematics and key dimensionless parameters comparable to the Reynolds quantity, Strouhal quantity, and lowered frequency is highlighted. many of the unsteady carry enhancement mechanisms also are addressed, together with modern vortex, swift pitch-up and rotational circulate, wake seize, and clap-and-fling.

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Extra resources for Aerodynamics of Low Reynolds Number Flyers

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4. Streamwise velocity profiles over the upper surface of an SD7003 airfoil with varying Reynolds numbers, at a fixed AoA of 4◦ . Inviscid as well as viscous flow solutions are shown. At Re = 106 , a short bubble is observed; otherwise, the velocity distribution largely matches that of the inviscid model. At a lower Reynolds number, Re = 4 × 104 , a long bubble after bursting is observed, causing significant impact on the velocity distribution. Finally, at Re = 2 × 104 , a complete separation with no reattachment is noticed.

Our main interest is on issues related to a Reynolds number of 105 or lower. 2 illustrates the aerodynamic performances and shapes of several representative airfoils under a steady-state free stream. A substantial reduction in the lift-to-drag ratio is observed as the Reynolds number becomes lower. The observed aerodynamic characteristics are associated with the laminar–turbulent transition process. For conventional manned aircraft wings, whose Reynolds numbers exceed 106 , the flows surrounding them are typically turbulent, with the near-wall fluid capable of strengthening its momentum by means of energetic “mixing” with the free stream.

2), the momentum-thickness jump is sensitive to the location of transition point in the separation bubble. Furthermore, because airfoil drag is directly affected by a momentumthickness jump, an accurate laminar–turbulent transition model is important for drag prediction. 4 illustrates the behavior of an LSB in response to the Reynolds number. The analyses are based on the XFOIL code (Drela, 1989), which uses the thin-layer fluid flow model, assuming that the transverse length scale is much smaller than the streamwise length scale.

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