Improvement of Aerodynamic Characteristics of an Airfoil by Surface Modification
Creators: name: Yy, Ss
Publisher: name: Figshare
Year: 2017
Subjects: subject: Mechanical Engineering
subject: FOS: Mechanical engineering
subject: Aerospace Engineering
subject: 90102 Aerospace Materials
subject: 90103 Aerospace Structures
subject: 90199 Aerospace Engineering not elsewhere classified
subject: 120401 Engineering Design Empirical Studies
subject: FOS: Other engineering and technologies
subject: 91503 Engineering Practice
subject: 90101 Aerodynamics (excl. Hypersonic Aerodynamics)
subject: 90107 Hypersonic Propulsion and Hypersonic Aerodynamics

description: The present work describes change in aerodynamic characteristics of an airfoil by applying certain surface modifications in form of dimples. At first surface modification that is considered here is hexagonal dimples on the wing model. A comparative study showing variance in lift and drag of modified airfoil model at different angle of attacks is done. The surface modification which is being considered in the given study are dimples of hexagonal shapes. Till now these have been ignored because dimples help in reduction of pressure drag. In case of aerodynamic bodies pressure drag is very little compared to bluff bodies. An airfoil is an aerodynamic body so dimples do not affect to its drag much at zero angle of attack, but as soon as airfoil attains some angle of attack, wake formation starts due to boundary layer separation. Application dimples on aircraft wing model works in same manner as vortex generators. They create turbulence which delays the boundary layer separation and reduces the wake and thereby reducing the pressure drag. This also assists in Lift of the aircraft. Most importantly this can be quite effective at different the angle of attacks and also can change angle of stall to a great extent. A stall is a condition in aerodynamics and aviation where the angle of attack increases beyond a certain point such that the lift begins to decrease. The angle at which it occurs is called the critical angle of attack or angle of stall .The results were in agreement that dimples on the surface aircraft wing model does not affect the pressure drag much since it is already aerodynamic in shape but it can affect its aerodynamics when the airfoil is at different angle of attacks. This project indicatess if the dimples that reduce a golf ball's drag, can also alter flow dynamics around airfoil for better aerodynamic efficiency. Dimples delay the boundary layer separation by creating more turbulence over the surface thus reducing the wake formation. This in turn reduces drag drastically. The airfoil profile considered in the present study is NACA-4415 with uniform cross-section throughout the length of airfoil. Subsonic flows are considered for the study. For design purpose solid works software is used. Two different models without dimples and with hexagonal dimples has been constructed. All the models are prepared by wood and the studies are conducted using 100×100×100 cm subsonic wind tunnel. From the investigations it has been observed that the flow separation on the airfoil can be delayed by using hexagonal dimples on the upper surface. Flow separation occurs at 12° angle of attack in the regular surface. But for surface having hexagonal dimples it will occurs at 16° angle of attack. That indicates the surface having hexagonal dimples successfully controls the flow separation and increases the lift force of an airfoil.