Parametric modelling of the iGREEN configuration
Aeroelasticity usually pursues the aim of predicting possible problems at an early stage of development to reduce development risks. The objective of using aeroelastic effects to optimise entire aircraft is more ambitious. In this case, the availability of appropriate global structural models – even at an early stage of the design – is a prerequisite. But, in many cases, such models are not available. For this reason, the fully parameterised model generation and design process MONA (ModGen & NASTRAN) was developed at the Institute of Aeroelasticity. This process consists of two components. First of all, the ModGen tool, which was developed by the Institute, is used to generate ‘modules’ for the required parametric simulation and optimisation models in the design process (for example, FE models, aerodynamic model, coupling model for aerodynamic, structural and mass models). After this, the manoeuvre and gust loads are determined with MSC.NASTRAN and sizing is carried out with structural optimisation methods.
The main focus of the ModGen program is the generation of complete aeroelastic analysis models for aircraft, with the focus on wing modelling. The design process aims for parametric structural models that are sufficiently global to enable statements with regard to the dynamic characteristics of the aircraft to be made quickly, but which are also realistic and detailed enough to take relevant local effects such as attachment stiffness into account. For the construction of the model, internal, realistic structures as well as the external geometry are defined. Modelling of stiffness and masses initially concentrates on the load-bearing structure. The systems, freight, passengers and fuel are defined as additional individually distributed masses. The output for the full model (see image) includes the finite element model of the structure, aerodynamic modelling for doublet lattice analyses, interfaces for the connection of various model components (wings, fuselage and empennage), as well as the definition of optimisation variables and the restrictions for the following sizing stage. Both isotropic as well as fibre-reinforced composite materials can be taken into account in the model.