Flow structures around a flapping wing considering ground effect

• Published in: Experiments in fluids Vol. 54; no. 7; pp. 1 - 19
• Main Authors: Van Truong, Tien, Kim, Jihoon, Kim, Min Jun, Park, Hoon Cheol, Yoon, Kwang Joon, Byun, Doyoung
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2013; Springer
• Subjects: Aerodynamics; Applied fluid mechanics; Applied sciences; Beetles; Computational fluid dynamics; Computer science; control theory; systems; Control theory. Systems; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Exact sciences and technology; Flapping wings; Fluid dynamics; Fluid flow; Fluid- and Aerodynamics; Fundamental areas of phenomenology (including applications); Ground effect (aerodynamics); Heat and Mass Transfer; Physics; Research Article; Robotics; Takeoff; Wings (aircraft); Lead Edge Vortex; Hind Wing; Digital Particle Image Velocimetry; Ground Effect; Stroke Plane; Wing; Moving robot; Swirling flow; Insecta; Speed measurement; Aerodynamics; Experimental study; Robotics; Ground effect; Biomimetics; Unmanned aerial vehicle; Wing beat; Test facility; Arthropoda; Particle image velocimetry; Model test; Invertebrata; Miniaturized design
• ISSN: 0723-4864; 1432-1114
• DOI: 10.1007/s00348-013-1575-6

Over the past several decades, there has been great interest in understanding the aerodynamics of flapping flight, namely the two flight modes of hovering and forward flight. However, there has been little focus on the aerodynamic characteristics during takeoff of insects. In a previous study we found that the Rhinoceros Beetle ( Trypoxylusdichotomus ) takes off without jumping, which is uncommon for other insects. In this study we built a scaled-up electromechanical model of a flapping wing and investigated fluid flow around the beetle’s wing model. In particular, the present dynamically scaled mechanical model has the wing kinematics pattern achieved from the real beetle’s wing kinematics during takeoff. In addition, we could systematically change the three-dimensional inclined motion of the flapping model through each stroke. We used digital particle image velocimetry with high spatial resolution, and were able to qualitatively and quantitatively study the flow field around the wing at a Reynolds number of approximately 10,000. The present results provide insight into the aerodynamics and the evolution of vortical structures, as well as the ground effect experienced by a beetle’s wing during takeoff. The main unsteady mechanisms of beetles have been identified and intensively analyzed as the stability of the leading edge vortex (LEV) during strokes, the delayed stall during upstroke, the rotational circulation in pronation periods, and wake capture in supination periods. Due to the ground effect, the LEV was enhanced during half downstroke, and the lift force could thus be increased to lift the beetle during takeoff. This is useful for researchers in developing a micro air vehicle that has a beetle-like flapping wing motion.