A Transition Model Based Aerodynamic Adjoint Optimization Design Method for Aircraft
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Laminar flow is one of the key technologies for the development of green aviation in the future. An efficient and robust optimization design method capable of handling large-scale design variables is one of the key links to promote the engineering application and transformation of laminar flow technology. Based on a high-fidelity Reynolds-Averaged Navier-Stokes (RANS) solver, combined with the Shear-Stress Transport (SST) turbulence model and the Gamma-Theta transition model, accurate simulation of the transition-turbulence phenomenon on the wing surface is achieved. Through the variation of the residual terms of the transition-turbulence model, the establishment of the left-hand side terms of the coupled adjoint equation considering the transition-turbulence effect is realized. Furthermore, combined with the chain rule of differentiation and the LU-SGS implicit time-marching algorithm, an efficient solution method for the coupled adjoint equation is developed. Eventually, a discrete adjoint-based optimization design method for aircraft laminar flow is established. Laminar flow optimization design is carried out for configurations such as high-altitude long-endurance (HALE) unmanned aerial vehicles (UAVs), which significantly delays the transition positions of each section. The optimization results demonstrate that the established gradient-based optimization method for laminar flow wings can effectively address complex three-dimensional laminar flow wing optimization problems.
