Toward the feasible solution of a long-lasting dynamic similitude problem

Abstract

Dynamic similar models are designed to study the flight behavior of the full-scale aircraft in early design stages. Due to physical and operational constraints, full dynamic similarity between the scaled-down model and full-scale aircraft is not feasible. Thus, the scale model would be flying at different Reynolds number and Mach number. A given aircraft configuration with specific aerodynamic characteristics will have different performance if Mach number and Reynolds number are changed considerably, which results in different dynamic behavior of the scale model. To compensate for these dissimilarities, it is proposed to modify the airfoil geometry of the scale model to preserve aerodynamic similarity. In this study, based on the flight regime and design requirements, maximum thickness of the airfoil, maximum camber, and their respective location are modified to preserve aerodynamic characteristics at different Mach and Reynolds numbers. Geometry optimization was performed using Particle Swarm Optimization and the geometry optimization results show that it is possible to mitigate the change in Reynolds and Mach number in various flight conditions. It has been shown that optimized geometries of all test cases had airfoils with lower maximum thickness and slightly higher maximum camber.