跨声速层流翼型的混合反设计/优化设计方法

跨声速层流翼型设计须兼顾优良的超临界特性和自然层流特性，因而对设计方法提出了更高的要求。针对现有反设计方法和直接优化设计方法的不足，发展了一种适用于跨声速层流翼型的混合反设计/优化设计方法。该方法引入了基于经验的局部流场特征作为反设计目标，翼型性能指标作为直接优化设计目标，然后加权形成了混合反设计/优化设计总目标，并同时考虑了气动和几何约束。优化算法采用基于自适应并行加点技术的代理优化，流动数值模拟采用耦合基于线性稳定性理论的e^N转捩自动判定的雷诺平均Navier-Stokes（RANS）方程求解器。针对现代中短程民用客机需求，以NPU-LSC-72613翼型为基准，开展了层流翼型减阻的混合反设计/优化设计。分别将局部目标压力分布、总阻力作为反设计和直接优化设计目标，得到了较好的优化结果，验证了方法的有效性。经过2轮优化结果显示混合反设计/优化设计总目标显著下降。所设计翼型吸力面局部压力分布与目标压力分布基本一致，总阻力下降15.5%；吸力面和压力面层流范围均大于55%倍弦长，激波强度显著减弱，说明所设计翼型同时具有优良的超临界和层流特性。将所设计翼型配置到机翼上，通过三维数值模拟进行校验，结果显示所设计跨声速层流机翼升阻比提高了6.64%，在一定升力系数范围内，气动性能均有显著提高，验证了所设计跨声速层流翼型在机翼设计中的适用性。

A hybrid inverse/direct optimization design method for transonic laminar flow airfoil

To reach good qualities of supercritical and laminar characteristics, the design of transonic natural laminar flow airfoil, suitable for short/medium civil aircraft, is much more complex compared to conventional supercritical airfoil. Aimed to overcome the shortcomings of the current inverse and direct methods, a hybrid inverse/direct optimization method suitable for transonic natural laminar flow airfoil is put forward. A hybrid objective is formulated by weighting the objective of inverse design defined by local target flow characteristics based on experience and the objective of direct optimization design defined by the specific performance index. Constraints concerning flow and geometry are considered as well. Optimization algorithm is based on a surrogate model with adaptive parallel infilling techniques. Flow field is simulated by a Reynolds-Averaged Navier-Stokes (RANS) equations solver with functionality of automatic transition prediction. The optimization design of a transonic natural laminar flow airfoil is carried out by setting the prescribed local target pressure distribution as the inverse design objective and the total drag coefficient as the direct optimization objective, yielding satisfactory results and verifying the validity of the method. With two rounds of optimization, the design objective of the hybrid inverse/direct optimization is dramatically decreased:local target pressure distribution is realized on the designed airfoil. And the total drag is reduced by 15.5%. Laminar flow regions on both sides of the designed airfoil are larger than 55% chord. The lift-to-drag ratio of the transonic natural laminar flow wing with the designed airfoil is 6.64% larger than that with the base airfoil. And the designed wing shows better aerodynamic performance within certain range of lift coefficient, which verifies the effectiveness of the hybrid inverse/direct method for natural laminar flow airfoil design problems.