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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2018, Vol. 39 ›› Issue (12): 122219-122219.doi: 10.7527/S1000-6893.2018.22219

• Fluid Mechanics and Flight Mechanics • Previous Articles     Next Articles

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

CHEN Jing1,2, SONG Wenping1, ZHU Zhen1, XU Zhenming1, HAN Zhonghua1   

  1. 1. National Key Laboratory of Science and Technology on Aerodynamic Design and Research, School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China;
    2. Wuhan Second Ship Design and Research Institute, Wuhan 430064, China
  • Received:2018-04-18 Revised:2018-05-30 Online:2018-12-15 Published:2018-07-20
  • Supported by:
    National Natural Science Foundation of China (11772261); Aeronautical Science Foundation of China (2016ZA53011); ATCFD Project (2015-F-016)

Abstract: 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.

Key words: laminar flow airfoil, surrogate optimization, inverse design, direct optimization design, transition automatic prediction

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