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几何参数化和网格变形是飞行器气动外形数值优化迭代过程中的两个关键技术。基于非均匀有理B样条(NURBS)的自由型面变形(NFFD)技术对几何表示形式具有普适性,距离权函数(DWF)网格变形技术具有计算快速和网格拓扑无关性,两者广泛应用于曲面优化。基于NFFD技术改进了反求参数的Newton迭代算法,并通过提高物面附近网格刚度改进的距离权函数(IDWF)技术使其适用于更大程度的网格变形。还提出了改进后的参数化和网格变形两种技术并行计算的具体实现算法。结合离散伴随方法,使用参数化和网格变形技术,实现了由NACA0012初始翼型到飞翼标准翼型EH1590的反设计;针对某飞翼标模完成了单点全机升阻比优化,升阻比提高约18%。数值结果表明,建立的NFFD和IDWF动网格技术可满足飞翼气动外形优化参数化和快速网格变形的需求。
Geometrical parameterization and grid deformation are two key technologies in numerical optimization iteration of aerodynamic shape of aircraft. Free-form surface deformation (NFFD) based on NURBS is universal for geometric representations. Distance weighting (DWF) grid deformation techniques are computationally fast and grid topological independent, both Widely used in surface optimization. The Newton iterative algorithm based on NFFD technique is improved and the improved inverse distance function (IDWF) technique is proposed to improve the mesh deformation by increasing the stiffness of the mesh around the object plane. Also put forward the improved parameterization and grid deformation two kinds of technology parallel computing algorithm. Combined with the discrete adjoint method, using the parameterization and the grid deformation technique, the inverse design of the NACA0012 initial airfoil to the flying wing standard airfoil EH1590 was realized. For a flying wing model, the single point full-lift / Resistance increased by about 18%. The numerical results show that the established NFFD and IDWF moving grid technology can meet the aerodynamic profile optimization parameterization and rapid grid deformation requirements.