Aerodynamic Optimization And Application Of Low Reynolds Number Airfoil

The research and development of high-performance airfoil is a basic research in the development of aircraft, and the airfoil's aerodynamic performance has a decisive influence in aerodynamic performance of aircraft, too. Currently, small Unmanned-Aerial-Vehicles (UAV) has become a hot point in the research field of UAVs, however, low Reynolds number airfoil's aerodynamic characteristics is more important for small UAVs. Consequently, it becomes necessary to research and optimize the aerodynamic characteristics of low Reynolds number airfoil. As a branch of Aerodynamic Optimization and Design, CFD-based aerodynamic shape optimization technology plays an important role in this filed at present, and it takes on an outstanding effect, too. In order to take advantage of the benefits of aerodynamic shape optimization thoroughly, without improving CFD's numerical accuracy and efficiency, it is needed to do further research on parameterization of geometric models, design of experiments, surrogate models, optimization algorithms etc. In addition, it is also needed to expand the applications of aerodynamic optimization continuously. Regarding these background points, the main research focus was laid on aerodynamic shape optimization of low Reynolds number airfoil, and the main work of this thesis may be described in the following several aspects:(1) The principle and basic framework of the CFD-based aerodynamic shape optimization technology were introduced, and the basic method of low Reynolds number airfoil's aerodynamic shape optimization was revealed, too. As to parametric description of airfoil, sampling of experiments, CFD simulation, Kriging surrogate model, genetic algorithm, which composed aerodynamic optimization of low Reynolds number airfoils, were studied roundly.(2) A variety of parameterization described methods of airfoil were studied, the current universal Hicks-Henne shape function method and Parsec method were studied deeply. The advantages and disadvantages of each method and the effects on the description of the airfoil were both compared, and the causes were analyzed. Another improved Hicks-Henne shape function method was finally used as the parametric description of airfoils. As a result, description distortion about the whole airfoil and inaccuracy near the trailing edge which often occur when using the traditional Hicks-Henne shape function method were all eliminated. At the end, some valuable experiences on setting the bounds of design parameters of the optimization were summarized.(3) The single-point and multi-point aerodynamic shape optimization for airfoils were studied. The single-point optimization of the airfoil with the goal of maximizing its lift to drag ratio was firstly accomplished, and then, taking the power factor as the optimization goal, the multi-point optimization was achieved successfully, and the optimized airfoil enlarged the velocity range with optimal performance of the aircraft and reduced the power consumption in flight.(4) The optimized airfoil using multi-point aerodynamic shape optimization was applied on the design of a solar powered UAV. The UAV was manufactured and tested, power requirement in level flight was measured via flight tests. The results showed that the minimum power requirement in level flight was only 50 W, which satisfied the expected performance design objective.