investigation of surface roughness on aerodynamic characteristics of missiles

nowadays, we live in a world which quality, speed, accuracy and cost are the most important parameters in parts' design and manufacturing. due to the complexity of part manufacturing, traditional and nontraditional manufacturing techniques are used. aerodynamic tests usually requires one or several models for testing in wind tunnels and these models typically have particular complexities in which necessitates different techniques such as machining, casting or rapid prototyping in order to manufacture them; however, these techniques imply certain advantages and disadvantages. selection of an optimal method affects the results and quality of manufacturing. in this study, the surface roughness experimental effect of a projectile on its aerodynamic coefficients is investigated. for this purpose, three projectiles with three levels of high, medium and rough surface quality were built and analyzed in different angles of attack and velocities, the aerodynamic coefficients and the ratio of lift to drag. the results indicated that at high velocities and high angles of attack, it is better to use a model with the highest surface quality because it reduces the drag and increases the ratio of lift to drag, thus has influence on the aerodynamic coefficients and with increasing roughness, critical reynolds number is also reduced.