基于DFFD技术的翼型气动优化设计

开展了直接操作自由变形（DFFD）技术在翼型参数化及翼型气动外形优化设计中的应用研究，应用该方法可以对翼型形状进行直接操纵和精细的局部修型，从而在一定程度上克服了自由变形（FFD）技术无法直接指定几何外形变形量的局限性。通过最小二乘模式根据翼型表面直接操作点的位移求解各个FFD控制点相应的位移，将翼型设计参数从FFD控制点转化为翼型表面的直接操作点，从而有效地减少了高阶FFD控制体进行翼型参数化时的设计参数个数。算例表明，相比于FFD方法，DFFD方法不仅具备直接操纵翼型几何外形的能力，更具物理直观性，并且比FFD方法具有更好的局部变形特性。运用该技术结合遗传算法对RAE2822翼型进行了气动减阻设计，显著减小了设计状态下翼型的阻力，并且可以有效施加如前后梁位置翼型厚度等工程实用的几何约束，证明了该方法的有效性。

Aerodynamic Optimization Design of Airfoil Using DFFD Technique

This paper studies the directly manipulated free form deformation (DFFD) technique applied to airfoil geometry parameterization and aerodynamic shape optimization. By this method the direct manipulation and refined local shaping of an airfoil can be achieved, which overcomes the disadvantage of the traditional free form deformation (FFD) technique. The displacements of the FFD control points are computed by the least-square method using the specified displacements of some pilot points of the airfoil, so that the design variables are transformed from the FFD control points to the pilot points, which reduces the number of design variables when using a high order FFD control volume to achieve shape optimization. The case study shows that, compared with FFD, DFFD is of better physical intuition and geometry deforming capability. Finally, DFFD is applied to the aerodynamic shape optimization of RAE2822 airfoil together with a genetic algorithm, which shows that this approach is feasible and efficient, and it can be coupled with effective geometrical constraints.