This paper describes the work performed by ONERA and Airbus to solve several aerodynamic optimization problems proposed in 2013 by the AIAA Optimization Discussion Group (ADODG). Three of the four test cases defined by this group have been addressed, respectively a 2D invicid, non-lifting, transonic airfoil optimization problem, a 2D RANS transonic airfoil optimization problem and a 3D RANS transonic wing optimization problem. All three problems have been investigated using local, gradient-based, optimization techniques and the elsA[1][2] CFD software and its adjoint capability. Through these three optimization exercises, several generic issues introduced by aerodynamic gradient-based optimization have been investigated. Among the investigated aspects are the impact of the geometry parameterization (nature and dimension), of the accuracy of the gradient calculation method, optimization algorithm and presence of constraints in the optimization problem. NomenclatureC p = pressure coefficient CD = total drag coefficient CDp = pressure drag coefficient CDf = friction drag coefficient CDw = wave drag coefficient CDvp = viscous pressure drag coefficient CL = lift coefficient CM = pitching moment coefficient c ref = chord reference d.c. = drag counts (0.0001) Ma = Mach number Re = Reynolds number AoA = Angle of attack f = objective function g = inequality constraint 1

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In the present work, the CFD analysis and local shape optimization of a boxwing architecture designed during the early stages of the PARSIFAL project are addressed in order to assess and improve its transonic aerodynamic performance. The assessment of the baseline configuration is carried out by means of highfidelity RANS computations while an Euler-based workflow is employed for the optimization study. In both cases, CFD computations are supplemented by a far-field drag post-processing to inspect the behavior and the impact of the different drag sources (induced, wave, pressure and viscous dissipation) on the aerodynamic performance. Results obtained from the optimization of local twist and camber parameters for the isolated boxwing lifting-system are presented and discussed. The optimization successfully achieves a great reduction of the compressibility effects affecting the baseline configuration, leading to a substantial improvement of the aerodynamic performance at cruise and higher values of the lift coefficient.

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