In this study, the wing design problem for different planforms for supersonic transport (SST) under supersonic and transonic cruise conditions is discussed to obtain knowledge of the supersonic air-foil from the viewp...In this study, the wing design problem for different planforms for supersonic transport (SST) under supersonic and transonic cruise conditions is discussed to obtain knowledge of the supersonic air-foil from the viewpoint of wing planform dependency. Two types of planforms were considered—a cranked arrow wing with a high sweep-back angle and a tapered wing with a low sweep- back angle. The optimum airfoils of these planforms were designed by efficient global optimization, which combined the evolutionary algorithm with the Kriging surrogate model. To acquire design knowledge, the functional analysis of variance was applied to the solution space and the design space. The design results show that the optimum airfoil and the contribution ratios of design variables for the airfoils of the two planform are different.展开更多
Abstract A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport （SST） k-w turbulence model to predict the trans...Abstract A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport （SST） k-w turbulence model to predict the transition region for a laminar-turbulent boundary layer. The non-uniform free-form deformation （NFFD） method based on the non-uniform rational B-spline （NURBS） basis function is introduced to the airfoil parameterization. The non-dominated sorting genetic algorithm-II （NSGA-II） is used as the search algo- rithm, and the surrogate model based on the Kriging models is introduced to improve the efficiency of the optimization system. The optimization system is set up based on the above technologies, and the robust design about the uncertainty of the Mach number is carried out for NASA0412 airfoil. The optimized airfoil is analyzed and compared with the original airfoil. The results show that natural laminar flow can be achieved on a supercritical airfoil to improve the aerodynamic characteristic of airfoils.展开更多
A transonic airfoil designed by means of classical point-optimization may result in its dramatically inferior performance under off-design conditions. To overcome this shortcoming, robust design is proposed to find ou...A transonic airfoil designed by means of classical point-optimization may result in its dramatically inferior performance under off-design conditions. To overcome this shortcoming, robust design is proposed to find out the optimal profile of an airfoil to maintain its performance in an uncertain environment. The robust airfoil optimization is aimed to minimize mean values and variances of drag coefficients while satisfying the lift and thickness constraints over a range of Mach numbers. A multi-objective estimation of distribution algorithm is applied to the robust airfoil optimization on the base of the RAE2822 benchmark airfoil. The shape of the airfoil is obtained through superposing ten Hick-Henne shape functions upon the benchmark airfoil. A set of design points is selected according to a uniform design table for aerodynamic evaluation. A Kriging model of drag coefficient is constructed with those points to reduce computing costs. Over the Mach range from 0.7 to 0.8, the airfoil generated by the robust optimization has a configuration characterized by supercritical airfoil with low drag coefficients. The small fluctuation in its drag coefficients means that the performance of the robust airfoil is insensitive to variation of Mach number.展开更多
为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行...为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行数值模拟分析。研究发现,在上翼面存在激波的情况下,下表面射流在增大翼型升力的同时也增大了波阻。提出下表面射流伴随优化进程的射流翼型一体优化思路。采用基于Kriging代理模型的优化方法,以最大化升阻比为目标,对RAE2822翼型分别进行了基准外形优化和带下表面射流(cμ=0.0002)的翼型优化。结果表明:在Ma=0.73、Re=6.5×10^(6)、α=2°的工况下,相较于基准翼型,下表面射流翼型等效升阻比提高了4.9%,下表面射流优化翼型等效升阻比提高了26.2%。带下表面射流翼型的射流翼型一体优化设计方法,能够显著提高超临界翼型的等效升阻比,研究结果有助于下表面射流的应用研究。展开更多
Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Str...Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using non- symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil＇s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interac- tions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter＇s wing.展开更多
文摘In this study, the wing design problem for different planforms for supersonic transport (SST) under supersonic and transonic cruise conditions is discussed to obtain knowledge of the supersonic air-foil from the viewpoint of wing planform dependency. Two types of planforms were considered—a cranked arrow wing with a high sweep-back angle and a tapered wing with a low sweep- back angle. The optimum airfoils of these planforms were designed by efficient global optimization, which combined the evolutionary algorithm with the Kriging surrogate model. To acquire design knowledge, the functional analysis of variance was applied to the solution space and the design space. The design results show that the optimum airfoil and the contribution ratios of design variables for the airfoils of the two planform are different.
文摘Abstract A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport （SST） k-w turbulence model to predict the transition region for a laminar-turbulent boundary layer. The non-uniform free-form deformation （NFFD） method based on the non-uniform rational B-spline （NURBS） basis function is introduced to the airfoil parameterization. The non-dominated sorting genetic algorithm-II （NSGA-II） is used as the search algo- rithm, and the surrogate model based on the Kriging models is introduced to improve the efficiency of the optimization system. The optimization system is set up based on the above technologies, and the robust design about the uncertainty of the Mach number is carried out for NASA0412 airfoil. The optimized airfoil is analyzed and compared with the original airfoil. The results show that natural laminar flow can be achieved on a supercritical airfoil to improve the aerodynamic characteristic of airfoils.
基金National Natural Science Foundation of China (10377015)
文摘A transonic airfoil designed by means of classical point-optimization may result in its dramatically inferior performance under off-design conditions. To overcome this shortcoming, robust design is proposed to find out the optimal profile of an airfoil to maintain its performance in an uncertain environment. The robust airfoil optimization is aimed to minimize mean values and variances of drag coefficients while satisfying the lift and thickness constraints over a range of Mach numbers. A multi-objective estimation of distribution algorithm is applied to the robust airfoil optimization on the base of the RAE2822 benchmark airfoil. The shape of the airfoil is obtained through superposing ten Hick-Henne shape functions upon the benchmark airfoil. A set of design points is selected according to a uniform design table for aerodynamic evaluation. A Kriging model of drag coefficient is constructed with those points to reduce computing costs. Over the Mach range from 0.7 to 0.8, the airfoil generated by the robust optimization has a configuration characterized by supercritical airfoil with low drag coefficients. The small fluctuation in its drag coefficients means that the performance of the robust airfoil is insensitive to variation of Mach number.
文摘为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行数值模拟分析。研究发现,在上翼面存在激波的情况下,下表面射流在增大翼型升力的同时也增大了波阻。提出下表面射流伴随优化进程的射流翼型一体优化思路。采用基于Kriging代理模型的优化方法,以最大化升阻比为目标,对RAE2822翼型分别进行了基准外形优化和带下表面射流(cμ=0.0002)的翼型优化。结果表明:在Ma=0.73、Re=6.5×10^(6)、α=2°的工况下,相较于基准翼型,下表面射流翼型等效升阻比提高了4.9%,下表面射流优化翼型等效升阻比提高了26.2%。带下表面射流翼型的射流翼型一体优化设计方法,能够显著提高超临界翼型的等效升阻比,研究结果有助于下表面射流的应用研究。
文摘Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using non- symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil＇s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interac- tions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter＇s wing.
