Aerodynamic Optimization Design on Supersonic Transports Considering Sonic Boom Intensity

考虑声爆特性的超声速客机气动优化设计

School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China

Received: 11 April 2019

Abstract

It is key points to improve the aerodynamic efficiency and decrease the sonic-boom intensity for the supersonic aircraft design. Sonic-boom prediction method with high precision combining the near-field sonic-boom prediction based on Reynolds-Averaged Navier-Stokes equations and the far-field sonic-boom prediction based on waveform parameter method is firstly established. Then the gradient of sonic boom with respect to the design variables is calculated by the finite difference method and is combined with the gradient of the aerodynamic object by the discrete adjoint technique, acting as the gradient of the weighed object function. Assembling two gradients, the optimization system couples Free Form Deform method、the dynamic mesh technique based on Inverse Distance Weighting interpolation method、the gradient-based optimization algorithm based on the sequential quadratic programming. Using the aerodynamic optimization system considering the sonic boom intensity, the paper conducts a nose angle deflection optimization design and an elaborate aerodynamic optimization including huge design variables and constraints on a supersonic business jet, while the optimization objects are the weighed object and the supersonic cruise drag coefficient. The results show that the nose is deflected downward and the shock wave pattern is changed, leading to a lower far-field maximum overpressure; the drag is decreased by 15.8 counts, and the wing load is moved inboard, also, the pressure drag of the outer wing reduces. Meanwhile, the pressure distribution in the outer wing has a weaker adverse pressure gradient and a more gentle pressure recovery. After optimization, the low-drag and low-sonic boom configuration is obtained, which verified the effectiveness of the optimization system.

摘要

提高巡航气动效率和降低声爆强度是超声速客机设计的关键。首先建立了基于RANS方程的近场CFD预测和基于波形参数法的远场预测相结合的高精度声爆评估方法，然后采用有限差分法求解声爆目标对设计变量的梯度，与由离散伴随方程法求解的气动目标函数的梯度进行组装，作为权重目标值的梯度，并耦合自由型面变形参数化技术、基于逆距离权重插值算法的网格变形技术和序列二次规划算法，搭建了考虑声爆特性的气动优化系统。对超声速公务机翼身组合体构型先后进行了考虑声爆的机头偏转气动优化设计和机翼精细化气动减阻优化设计，优化目标分别为声爆值和阻力系数的权重之和、超声速巡航点阻力系数。结果表明，优化后机头下偏削弱了头部向下传播的激波强度，从而减小了远场声爆最大过压值；机翼精细化设计后阻力减幅达9.5%，载荷内移，外翼段压差阻力减小，同时压力分布形态表现出逆压梯度减弱、压力恢复更加平缓的特征。气动声爆综合特性明显优于初始构型，验证了优化系统的有效性。