1. Hybrid inverse/optimization design method for rigid coaxial rotor airfoils considering reverse flow
- Author
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Shang-Bin Li, Wenping Song, Shao-Qiang Han, Yong-Feng Lin, and Zhong-Hua Han
- Subjects
Airfoil ,0209 industrial biotechnology ,Computer science ,Aerospace Engineering ,Inverse ,Stall (fluid mechanics) ,02 engineering and technology ,Aerodynamics ,01 natural sciences ,010305 fluids & plasmas ,symbols.namesake ,020901 industrial engineering & automation ,Mach number ,Drag ,Control theory ,0103 physical sciences ,symbols ,Inverse optimization ,Coaxial - Abstract
Double-ended airfoils with round leading and trailing edges outperform conventional round-nose and sharp trailing-edge airfoils when used for the inboard part of a rigid coaxial rotor operating in forward flight, as reverse flow can occupy 80% surface of the retreating blade. However, aerodynamic design optimization for this kind of airfoils is challenging, since it is required to achieve drag reduction over a wider lift range in both forward and reverse flows but there is no method available currently. To address this problem, this article proposes an efficient hybrid inverse/optimization design method that combines inverse design and direct optimization within a surrogate-based optimization (SBO) framework. The weighted objective function consists of two components: prescribed pressure distributions and total drag. The resulting constrained optimization problem is solved by using kriging surrogate model and dedicated infill-sampling method. The proposed method is demonstrated by aerodynamic shape optimizations of a DBLN-526 airfoil and an elliptical airfoil and compared with direct optimization method. For DBLN-526 airfoil case, 7%–30% drag reduction is achieved in the range from zero lift to maximum lift and the optimum airfoil features better stall characteristics. For the case of elliptical airfoil of 40% thickness, significant drag reduction is achieved in both forward and reverse flows and the optimum airfoil features more robust aerodynamic performance at off-design Mach numbers. The results confirm that the proposed method outperforms the conventional direct optimization method and more practical for aerodynamic shape optimization of double-ended airfoils.
- Published
- 2019