Session 6: Enabling technologies

A sensitivity study based on the High-Dimensional Model Representation (HDMR) approach is used to assess the impact of changes in the operating conditions of a strut-braced airframe on the aerodynamic performance. Changes in cruise speed, altitude and angle of attack are considered to quantify the robustness of the airframe design with respect to perturbations to its nominal cruise conditions. A comparative analysis is also presented for the same airframe without a strut, i.e. an equivalent cantilever wing airframe. The comparison indicates that the presence of a strut does not have a major influence on the sensitivity, i.e. the gradients of aerodynamic drag.

With higher wing aspect ratio of a transport aircraft, the wing loads generally also increase and thus the required structural weight. Active load alleviation can help to shift the multidisciplinary optimum towards higher aspect ratios. To study this technology, fluid-structure coupled simulations are performed for quasi-steady pitching maneuvers of a large transport aircraft with a load alleviation system consisting of trailing edge flaps and droop noses at the leading edge. For the fluid part of the simulation, a RANS approach is used, whereas the structural simulation is based on a linear modal model. The selected maneuvers are located on the lift boundary of the maneuver envelope at maximum load factor, as not only are the structural loads high here, but also redistributing lift for load alleviation is especially challenging as the wing is close to stall. For a target value of 33% reduction in wing bending loads, which is derived from the CS-25, the effects of applying load alleviation on wing loads, deformations and aircraft maneuverability are investigated. It is found that the desired reduction of wing bending loads can be achieved for all maneuvers considered, while controlling the torsional moment turns out to be more difficult, especially on the outer wing. A loss of maneuverability due to load alleviation is observed for only one of the maneuvers, while for the other maneuvers the maneuverability could even be increased. Furthermore, also other potential applications of the considered flap system are explored. For example, it is found that the flap system could also be used to achieve a reduction in cruise drag of up to 1.8% by adjusting the spanwise lift distribution.

Modern composite structures, such as an aircraft wingbox, are typically very complex structures 10s of meters long. A single-scale analysis of an aircraft winbox with the level of detail required to represent damage propagation within composite plies is computationally unfeasible. In fact, even successfully modelling a complete aircraft wingbox with the level of detail required to reliably identify damage hotspots is computationally challenging; for instance, a non-linear wingbox simulation, capable of supporting the prediction of failure phenomena, will involve 100's of interacting parts and may exceed 100MDoF in size.  Solution of a single configuration scenario will generate a results database >100Gb in size, containing billions of individual failure indices and damage variables --- manual analysis of data on such a scale is intractable.

In this work, we present a redesign of the traditional failure modelling approaches specifically aimed at very large engineering structures. Specifically, we present (i) a harmonized modelling framework across various scales of analysis, as the same code is accessed via different subroutines that are used for different levels of idealization; (ii) a methodology for the calculation of high-value data directly in the computer cluster during the analysis, so that the output file eventually accessed by the user can be used effectively for decision making, such as identifying hot-spots for a multiscale analysis. We also show ongoing work whereby this high-value data is directly used by the large-scale analysis itself to identify hot-spots and adapt the mesh and idealization concurrently with the simulation.

Finally, we show how the framework described can support underpinning fundamental research with a clear route for industrial application, and how it provides an effective route for design of very large composites structures using physically-based and effective analysis methods.

This presentation will attempt to highlight the efforts of Prof Morlier's group at ISAE-SUPAERO/ICA to add more disciplines into the Multidisciplinary Design Optimization (MDO) of aerospace systems with a focus on HAR Aeroelastic Wing: Adding Control for Active Flutter Suppression [1,2] with Airbus Toulouse Adding Longitudinal stability for Load Alleviation [3] with Airbus Toulouse Adding LCA for CO2 footprint of a HALE [4] and Hybridization of a short range aircraft [5]