International Conference on Applied Mechanics and Industrial Systems (ICAMIS-Oman-2016), 6-8 December 2016, Muscat, Oman Aerodynamic Performance of Birds’ Airfoils Ranya Rhouma 1 , Abdulhaq Emhemmed 2 , and Ashraf A. Omar 3 1 Research Assistant, Department of Aeronautics, Faculty of Engineering, University of Tripoli 2 Teaching Assistant, Department of Aeronautics, Faculty of Engineering, University of Tripoli 3 Professor, Department of Aeronautics, Faculty of Engineering, University of Tripoli P.O. Box 81507, Tripoli, Libya. 3 Corresponding author: E-mail address: as.omar@uot.edu.ly Abstract In this work, the aerodynamics performance of four types of birds’ airfoils (Eagle, Stork, Hawk and Albatross) at low Reynolds number during fixed (un-flapping) gliding fight was investigated numerically using the open source CFD suite SU2. The effect of the angle of attack was also investigated. The results revealed that the stork has the greatest lift force coefficient followed by the albatross and eagle. However, at zero angle of attack, the albatross aerodynamic efficiency exceeds all the other birds by a significant amount. The aerodynamic performance of the birds’ airfoils was compared to a conventional low Reynolds number airfoil (Eppler 193). Keywords: Birds’ airfoil, CFD, lift coefficient, aerodynamics efficiency 1. Introduction Birds are a wonder of nature, their flapping and unflapping flight reach a level of perfection in all ways. In the area of low Reynolds number flow such as for micro air vehciles (MAV), lessons can be learned from birds’ body features and flight performance[6]. Since the early ages, ideas of flying emerged from attempting to imitate birds. In the 9th century, Abbas Ibn Firnas attempted to glide like a bird by covering himself with feathers and attaching wings to his body. The attempt inspired a lot of world scientist to copy the birds and study their bodies’ characteristics. The bird airfoil can be considered as a rigid body or as a flexible body. In addition, it can also be flapping or fixed. The airfoil has a good aerodynamic performance at a wide range of angle of attacks. Recently, researchers analyzed the drag of an eagle’s airfoil over Reynolds number in the range between 10 5 to 2 × 10 5 [2]. They concluded that drag is almost constant over a range of lift coefficients. Other research found that the bird’s airfoil has poor performance compared to high Reynolds number airfoils[10]. However, the performance should be compared to conventional low Reynolds airfoils. In addition, porosity of the wing is a feature of importance in birds’ aerodynamics. Researchers studying this effect divided the wing membranes to segments, solid and porous[4]. It was concluded that the slope of the lift coefficient decreased uniformly with increasing permeability. Also, it was observed that by keeping the width of the porous segment less than half the wing’s chord, the drag can be contained[5]. This paper addresses the aerodynamic performance for four different bird airfoils at low Reynolds number during fixed (unflapping) gliding flight. The four birds were the eagle, stork, hawk and albatross. The study was carried numerically using the open source CFD suite Stanford Unstructured (SU2) developed by