Bai Junqiang

Robust Design of Supercritical Wing Aerodynamic Optimization Considering Fuselage Interfering

Abstract Robust optimization approach for aerodynamic design has been developed and applied to supercritical wing aerodynamic design. The aerodynamic robust optimization design system consists of genetic optimization algorithm, improved back propagation (BP) neural network and deformation grid technology. In this article, the BP neural network has been improved in two major aspects to enhance the training speed and precision. Uniformity sampling is adopted to generate samples which will be used to establish surrogate model. The testing results show that the prediction precision of the improved BP neural network is reliable. On the assumption that the law of Mach number obeys normal distribution, supercritical wing configuration considering fuselage interfering of a certain aerobus has been taken as a typical example, and five design sections and twist angles have been optimized. The results show that the optimized wing, which considers robust design, has better aerodynamic characteristics. Whats more, the intensity of shock wave has been reduced.

A High-speed Nature Laminar Flow Airfoil and Its Experimental Study in Wind Tunnel with Nonintrusive Measurement Technique

Abstract This article deals with an experimental study on the aerodynamic characteristics of a low-drag high-speed nature laminar flow (NLF) airfoil for business airplanes in the TST27 wind tunnel at Delft University of Technology, the Netherlands. In this experiment, in an attempt to reduce the errors of measurement and improve its accuracy in high-speed flight, some nonintrusive measurement techniques, such as the quantitative infrared thermography (IRT), the digital particle imaging velocimetry (PIV), and the shadowgraphy, are applied to obtain precise data about transition locations, separation on trailing edges, and lift/drag characteristics. The experimental results reveal that, in the high-speed flight, small angles of attack are helpful in retaining long laminar flows, preventing the vortex at the trailing edge from moving forward and thus imparting the airfoil and the high-lift and low-drag characteristics. The comparison of the measured results to the calculated ones proves the acceptability of the airfoil and its aerodynamic characteristics satisfying the design requirements.

Mechanical and aerodynamic study of 2D trailing edge variable camber system for civil transport aircraft

Trailing edge variable camber (TEVC) system, as one of the new technologies exploited in transport aircraft design, has demonstrated great values in reducing fuel consumption. This paper focuses on mechanical and aerodynamic study of the TEVC system that could be used on the present and future civil aircraft. The TEVC system based on 2D cruise foil has been modeled and mechanism simulation demonstrates the excellence of kinematic characteristics. Besides, TEVC system performance for takeoff and landing has been evaluated. The results show the system could ensure takeoff and landing performance. Finally, TEVC system has been used to change trailing edge camber on the basis of 2D cruise foils. In the entire range of Cl available during cruise, the L/D of initial cruise foil has been improved, which shows great benefits on aerodynamics.

Aerodynamic Optimization Design of Civil Jet Wing-Body-Tail Configuration

针对典型跨声速民用客机的机翼/机身/平尾构型开展了基于离散伴随技术的气动外形优化设计方法研究,并采用自由型面变形（FFD）技术在优化设计过程中进行平尾的整体偏转,以实现最终设计结果全机俯仰力矩配平。采用基于雷诺平均Navier-Stokes（RANS）方程的离散伴随技术求解气动参数对设计变量的梯度,使梯度求解计算量与设计变量个数实现解耦,提高了优化效率。应用FFD技术对全机构型进行整体参数化,可通过FFD控制体控制机翼外形的变化以及平尾偏转,在实现机翼优化设计的同时通过偏转平尾来进行力矩配平,避免了单独优化机翼外形可能带来的额外配平阻力。采用序列二次规划算法进行基于梯度的优化设计并处理大规模的约束条件。以Drag Prediction Workshop IV Common Research Model作为初始构型进行了有/无力矩配平约束的优化设计,并在优化过程中施加升力约束以及几何约束。算例结果表明,优化后的气动外形显著改善了机翼表面压力分布,消除了激波,在力矩配平约束下的算例中,通过平尾的偏转实现了俯仰力矩配平下的机翼优化设计。