Multi-objective Optimization On Aerodynamic Performance Of Aerotrain Tandem Wing Layout

The layout of aerotrain tandem wings was researched to explore the influence of the tandem wings to aerodynamic performance of aerotrain and flow mechanisms between tandem wings.This paper aims to obtain a series of Aerotrain tandem wings layouts which have satisfying aerodynamic performance.The paper was divided into three parts: the wind tunnel experiments of aerotrain model,numerical simulation and the multi-objective optimization of layout of the tandem wings.In the part of wind tunnel experiments,the model of aerotrain with adjustable front and rear wings was designed and built.Then,according to the design driving condition of aerotrain,the applicable experimental bench was set up.The aerodynamic forces of aerotrain model were measured with different angles of attack of front or rear wings and the relative positions between front and rear wings.The visual results of flow condition on the upper surfaces of front and rear wings were achieved.The variation trend of the aerodynamic characteristics of aerotrain following the change of front or rear wings’ state parameters was discovered.The results of wind experiments can provide basis for numerical simulation.In the part of numerical simulation,a same digital model and similar computational domain were built,contrasting with the wind tunnel experiments.In terms of wind experimental results,after many tests,the mesh strategy was confirmed.This part explored the flow mechanism around the tandem wings via the numerical simulation.The results of the numerical simulation showed the airflow condition in the areas which between front and rear wings,behind the model and near the U-shaped guideway and lay the foundation of the researches about interaction of the airflows between tandem wings and the influence of the guideway to the aerodynamic performance of aerotrain.It is also a preparation for the next part: optimization of tandem wings layout.In the part of multi-objective optimization of layout of the tandem wings,the design variables and object functions were selected or confirmed according to the results and analysis of wind tunnel experiments and the numerical simulation.Kriging surrogate and NSGA-II algorithm were applied to optimized the aerodynamic characteristics of aerotrain model.The Pareto optimal solutions were found by genetic algorithm,and provided reference for determining the value of the design variables.Then the methods of Analysis of Variance and Self-organization Map,as two methods of data mining,were used to analyze the variables and objectives.The results of data mining showed the influence level,trend and regulation of each variable or the interaction between variables to the objectives.From the researches of this part,the conclusions were obtained: there is a contradictory between lift coefficient and drag coefficient of aerotrain.The tandem wing layout with great aerodynamic performance should have characteristics below: the ground clearance of front wing should be kept as small as possible,and the ground clearance of rear wing should be small but larger than the clearance of front wing;the angle of attack of front wing should be small and the angle of attack of rear wing should be a bit larger than front wing’s;large distance between front and rear wing.This paper has made an attempt to optimize the tandem wing layout of Aerotrain,and a set of effective method of optimization has been achieved.Then,this paper also lays a foundation for the next research about Multidirectional wings of Aerotrain.