A high-lift multi-element airfoil is optimized using a discrete adjoint method. The unstructured mesh RANS solver NSU2D is used as the flow and adjoint solver, and LBFGS-B, which is an optimization algorithm based on a quasi-Newton method, is used for driving shape optimization. In order to achieve a larger design space, the mesh deformation solver in NSU2D is modified by re-computing the mesh stiffness matrix during the mesh deformation process. Design variables consist of rigging parameters such as flap and slat gap, overlap and deflections, as well as surface shape parameters. Two kinds of objective functions are optimized, a drag coefficient constrained by a target lift coefficient and a maximum lift coefficient. In the first case, the optimized shape reduces drag by 64 counts, and in the second case, the maximum lift coefficient of the optimized shape is increased from the baseline value of 4.340 to 4.602.
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