Reduced drag, increased lift and, consequently, increased vital ratio and lift-to-drag coefficients are crucial in almost all efficient micro air vehicles. Riblet geometries use a variety of air vehicles. Further investigation on micro air vehicles is, however, necessary for enhanced development. Rectangular riblets on a rectangular micro air vehicle are computationally investigated. In this study, the governing equation of fluid flow is solved numerically; the turbulent model around the NACA S5020 airfoil section is covered by riblets either on both sides or on the upper side of the wings. Results show a difference of behavior in drag reduction due to the angle of attack on the airfoil. When the lift-to-drag coefficient of an angle of attack is at its maximum, an improvement can be observed, where lift-to-drag ratio increases, and drag decreases. Results for the two-side riblets show an increase in the lift-to-drag ratio as well; although the lift-to-drag coefficient and the drag reduction of riblets on both sides were comparatively less than that for riblets on the upside.
The Magnus effect is well known phenomena for producing high lift values from spinning symmetrical geometries such as cylinders, spheres, or disks. But, the Magnus force may also be produced by treadmill motion of aerodynamic bodies. To accomplish this, the skin of aerodynamic bodies may circulate with a constant circumferential speed. Here, a novel wing with treadmill motion of skin is introduced which may generate lift at zero air speeds. The new wing may lead to micro aerial vehicle configurations for vertical take-off or landing. To prove the concept, the NACA0015 aerofoil section with circulating skin is computationally investigated. Two cases of stationary air and moving air are studied. It is observed that lift can be generated in stationary air although drag force is also high. For moving air, the lift and drag forces may be adopted between the incidence angles 20 • to 25 • where lift can posses high values and drag can remain moderate. c ⃝
The Magnus force was successfully employed by Flettner in his ship Buckau operating with two large propelling cylinders. The spinning cylinders produced propulsive force from the wind on seas as a clean and free source of energy. The rise of fossil fuel costs, extinction of fossil fuel resources, and environmental issues such as global warming and pollutions produced by fossil fuels have caused a renew interest in Flettner type propulsion in naval ships. This is becoming a hot topic in Europe and the rest of world. Many other applications of producing high lift values from spinning symmetrical cylinders have failed due to high values of drag force and also rapid increase of frictional torques. In this paper, the new application of Treadmill-Magnus, wind driven propulsion system is introduced which can be effectively used for any size ships. To show validity of the concept, the NACA0020 aerofoil section with treadmill skin is computationally investigated at the low Reynolds number of 8.2 10 4. The viscous fluid flow solutions were obtained at variety of treadmill speeds of the aerofoil skin and different incident angles. The results show that high lift to drag ratios may be obtained using treadmill motion.
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