Masahiro Kanazaki

Multi-Objective Aerodynamic Optimization of Elements' Setting for High-lift Airfoil Using Kriging Model

In this paper, a multi-objective design optimization for a three-element airfoil consisted of a slat, a main wing, and a flap was carried out. The objective functions were defined as the maximization of lift coefficient at landing (Cl8) and near stall (Cl20)conditions simultaneously. Genetic Algorithm (GA) was used as an optimizer. Although it has advantage of global exploration, its computational cost is expensive. To reduce the computational cost, the kriging model which was constructed based on several sample designs was introduced. The solution space was explored based on the maximization of Expected Improvement (EI) value corresponding to objective functions on the kriging model to consider the predicted value by kriging model and its uncertainty. The improvement of the model and the exploration of the optimum can be advanced at the same time by maximizing EI value. In this study, 90 sample points are evaluated using the Reynolds averaged Navier-Stokes simulation (RANS) for the construction of the kriging model. Through the present exploration process, several designs were obtained with better performance than the baseline setting in each objective function. Functional Analysis of Variance (ANOVA) which is one of the data mining techniques showing the effect of each design variable on the objectives is applied. Main-effects of the design variables are calculated to recognize which design variable has the effect on the objective functions. This result suggests that the gap and the deflection of the flap have a remarkable effect on each objective function and the gap of the slat has an effect on Cl20.

High-lift Wing Design in Consideration of Sweep Angle Effect Using Kriging Model

In this paper, a multi-objective design exploration for a three-element airfoil which consists of a slat, a main wing, and a flap was carried out by paying attention to the span wise sweep angle effect for a civil aircraft. Reynolds Averaged Navier-Stokes Solver (RANS) was used for the evaluation during the design process. In this study, sweep angle effect is focused, and 2.5-dimensional span wise design was developed. In this calculation, two same planes were arranged along span wise direction. They were diagonally arranged to represent the sweep angle and periodic boundary condition was used for the simplified 2.5 dimensional span wise calculation. Kriging based Multi-objective Genetic Algorithm (MOGA) called efficient global optimization (EGO) and Analysis of Variance (ANOVA) were used for the design exploration. The objective functions were defined as the maximization of lift coefficient at landing and near stall conditions simultaneously. 90 sample points were evaluated for the construction of the Kriging model. Based on present evaluation method, the span wise flow was observed and it has an influence on the separation on the wing. Through the design exploration process, the differences of the designed results between 2.5D and 2D evaluation were observed by visualizing the design space. It was also observed that the span wise flow influences the separation point and suction peak on the wing elements.

Efficient Design Exploration of Nacelle Chine Installation in Wind Tunnel Testing

Design exploration of a nacelle chine installation was crried out. The nacelle chine is a device to improve the stall performance when multi-element high-lift devices were deployed. In this study, an efficient design process using Kriging surrogate model was proposed to decide the nacelle chine installation point in wind tunnel tests. The design process called ‘efficient design optimization (EGO)’ was conducted in the wind tunnel testing of JAXA high-lift aircraft model at JAXA Large-scale Lowspeed Wind Tunnel. The objective function for the EGO was to maximize the maximum lift. The installation points of the chine on the engine nacelle in the axial and chord-wise direction were designed, while the geometry of the chine was fixed. Through the design process in the wind tunnel test, an accurate surrogate model of the maximum lift by the chine location was efficiently obtained using expected improvement values as a criterion to select additional evaluation points. This method makes it possible not only to improve the accuracy of the response surface but also to explore the global optimum efficiently. Through this test, EGO process could be successfully applied to the design based on the wind tunnel test result.