INVESTIGATION ON LIFT AND DRAG COEFFICIENTS OF PROJECTILES AT VARIOUS ANGLES OF ATTACK

Abstract

Improvement in terminal accuracy is an important objective for future artillery projectiles. Generally, it is often associated with range extension and precision. This paper deals with the research of aerodynamic characteristics of anti-aircraft artillery and medium tank projectiles. In Bangladesh, a very little study is available for determining the aerodynamic characteristics of projectiles which are used in the Bangladesh army. When a projectile is launched it experiences a drag force which is more than the gravitational force due to the supersonic speed of the projectile. Aerodynamic characteristics are strictly related and will affect the stability of the projectiles, thus it is vital to obtain reliable aerodynamic characteristics estimation to carry out a good design of projectile. In this study, a set of a hollow projectile is considered since it shows good performance characteristics and it is easy to handle. For our research we have considered two types of anti-aircraft artillery projectiles, i.e. 57 mm & 37 mm and 125 mm medium tank projectile. Both experimental and numerical studies have been done on this type of projectiles. In this study, the main emphasis is given to determine the pressure coefficient, Drag coefficients, lift coefficient, and the behavior pattern of the projectiles at different angles of attack. To study the aerodynamic characteristics of the projectiles the experiment is conducted in an open circuit subsonic wind tunnel available at MIST where uniform flow velocity (4.7m/s) is maintained across the flow direction. For the experiment, the angle of attack is varied between 30° to 50° is considered with an interval of 5°. Here inclined manometer was used to find out the surface static pressure and then the pressure coefficient was determined from that. Finally, for the numerical scheme, the ANSYS Software was used to simulate the experiment. In this study, it was found that the drag and lift forces acting on the projectiles, increase with the increase in the size. In some cases, the drag and lift forces increase by more than 80%. The drag and lift forces also increased when the angle of attack increases. However, it was found that the rate of increasing the lift forces is higher (45%) than the drag forces for a case.