CFD based loads: Why and How

Abstract

The lecture motivates the use of Computational Fluid Dynamics for flight loads computations and highlights the necessary ingredients to achieve those simulations. CFD based aerodynamics account for aerodynamic nonlinearities such as flow separation and shock motion, which both occur in quasi-steady as well as in dynamic flight states. If no experimental data is available and no other means to correct potential based methods, it is the often the only option to quantify those aerodynamic nonlinearities. Also, less geometric simplifications are necessary in order to setup the physical models. The necessary ingredients are the spatial and temporal coupling of disciplines such as aerodynamics, flight dynamics and structural dynamics. Furthermore, a volume mesh deformation algorithm is required for the structural deformations as well as for control surface motion, with special care at junctions such as elevator/fuselage. Requirements for the CFD solver are outlined. The orchestration of all modules is done in the Software UltraFLoads, which relies on the FlowSimulator modules. The different scenarios show cased by virtual flight tests with the DLR-ATRA, DLR-ISTAR, fully nonlinear aerostructural analysis of very flexible transport aircraft wing, and closed loop discrete gust encounter simulations with a high aspect ratio wing aircraft.