Global Aero-Structural Design Optimization of More Flexible Wings for Commercial Aircraft

In the scope of the DLR project VicToria (Virtual Aircraft Technology Integration Platform), an integrated process for aero-structural wing optimization based on high fidelity simulation methods is continuously developed and applied. Based upon a parametric CAD model, flight performance under transonic flight conditions and maneuver loads are computed by solving the Reynolds-averaged Navier--Stokes equations (RANS). Structural mass and elastic characteristics of the wing are determined from structural sizing of the composite wing box for essential maneuver load cases using computational structural mechanics. Static aeroelastic effects are considered in all flight conditions by direct iterative coupling between the flow solver and the structural mechanics solver. Active maneuver load alleviation (MLA) is integrated in the process by a simplified modeling of control surface deflections by using a mesh deformation technique. Landing gear and control surface integration constraints were added compared to previous versions of the optimization process. Global aero-structural wing optimizations are successfully performed for wings with conventional composite wing box structure and for more flexible wings. The latter is accomplished by introducing modifications of the structural concept and the strain allowable. To reduce the CO2 emissions per passenger kilometer, the minimization of the combined fuel consumption for three typical flight missions represents the objective function. Wing optimizations are performed for variable and constant planform parameters as well as with and without consideration of MLA. A significant mass reduction of the optimized wing box is obtained with the more flexible wing concept, resulting in a drop in combined fuel consumption of about 3%. For wing optimizations with MLA the more flexible wing concept shows an additional reduction of the combined fuel consumption in the order of 2%. The more flexible wing concept results in optimized wing geometries with increased aspect ratio and reduced taper ratio