悬停状态直升机桨叶扭转分布的优化数值计算

 建立了一套基于高精度计算流体力学(CFD)技术和代理模型优化算法的旋翼气动外形设计方法。在该方法中,旋翼流场气动性能的计算采用了基于Navier-Stokes/Euler方程的CFD方法,并根据流场特点、精度和效率的要求采用Baldwin-Lomax(B-L)湍流模型,通量计算采用Roe-MUSCL格式进行。为提高网格生成质量和便于流场控制方程的求解,将流场分成两个区域,即围绕旋翼的黏性区和无黏的背景网格区。其中,桨叶网格使用了基于二维翼型网格的参数化方法生成,数值计算结果表明该方法有效地提高了网格生成质量及效率。在参考旋翼流场及桨叶细节流动分析的基础上给出设计变量及范围,有效减小了优化问题的规模;为满足优化和机理分析的需要,将基于置换遗传算法优化的拉丁超立方(PermGA LHS)方法和径向基函数(RBF)的代理模型优化方法引入到桨叶外形的优化设计中。首先以Helishape 7A旋翼为算例,检验了数值模拟方法的准确性。然后,应用所建立的优化方法针对旋翼负扭转分布进行了优化计算,结果表明优化后的旋翼悬停气动性能比优化前有了明显提高。

Numerical Optimization of Helicopter Rotor Twist Distribution in Hover

Based on high-accuracy computational fluid dynamics(CFD) methods and surrogate modeling optimization techniques,an optimization procedure for rotor aerodynamic shape design is established.Rotor aerodynamic performance is calculated by the CFD methods based upon Navier-Stokes/Euler equations and a Baldwin-Lomax(B-L) turbulence model is chosen to satisfy the flowfield characteristics,accuracy and efficiency requirements.Additionally,Roe-MUSCL scheme is employed to calculate the flux.In order to improve grid generating quality and facilitate the solution of the governing equations,the whole flowfield is divided into two zones,namely,a viscous zone around the rotor and an inviscous background zone.The blade grids are generated by a parameterized blade based on a 2D airfoil grid,and numerical examples demonstrate that the method can effectively improve grid generating quality and efficiency.By analyzing the flowfield of the reference rotor,design variables and constraints are selected to minimize the size of the optimization.To meet the needs of both optimization and mechanism investigation,an approach of optimization is established from permutated genetic algorithmic latin hypercube sampling(PermGA LHS) design and radial basis function(RBF).The Helishape 7A rotor case is first presented as validation of the numerical simulation method.Then,the optimization procedure is used to optimize rotor twist distribution.The results indicate that the aerodynamic performance of the optimized rotor in hover has been markedly improved.