跨声速层流翼型的混合反设计/优化设计方法

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.