Structural validation of a realistic wing structure: the RIBES test article

Several experimental test cases are available in literature to study and validate fluid structure interaction methods. They, however, focus the attention mainly on replicating typical cruising aerodynamic conditions forcing the adoption of fully steel made models able to operate with the high loads generated in high speed facilities. This translates in a complete loss of similitude with typical realistic aeronautical wing structures configurations. To reverse this trend, and to better study the aerolastic mechanism from a structural point of view, an aeroelastic measurement campaign was carried within the EU RIBES project. A half wing model for wind tunnel tests was designed and manufactured replicating a typical metallic wing box structure, producing a database of loads, pressure, stress and deformation measurements. In this paper the design, manufacturing and validation activities performed within the RIBES project are described, with a focus on the structural behavior of the test article. All experimental data and numerical models are made freely available to the scientific community

Performance evaluation of a piezoelectric energy harvester based on flag-flutter

In the last few decades, piezoelectric (PZT) materials have played a vital role in the aerospace industry because of their energy harvesting capability. PZT energy harvesters (PEH) absorb the energy from an operational environment and can transform it into useful energy to drive nano/micro-electronic components. In this research work, a PEH based on the flag-flutter mechanism is presented. This mechanism is based on fluid-structure interaction (FSI). The flag is subjected to the axial airflow in the subsonic wind tunnel. The performance evaluation of the harvester and aeroelastic analysis is investigated numerically and experimentally. A novel solution is presented to extract energy from Limit Cycle Oscillations (LCOs) phenomenon by means of PZT transduction. The PZT patch absorbs the flow-induced structural vibrations and transforms it into electrical energy. Furthermore, the optimal resistance and length of the flag is predicted to maximize the energy harvesting. Different configurations of flag i.e., with Aluminium (Al) patch and PZT patch for flutter mode vibration mode are studied numerically and experimentally. The bifurcation diagram is constructed for the experimental campaign for the flutter instability of a cantilevered flag in subsonic wind-tunnel. Moreover, the flutter boundary conditions are analysed for reduced critical velocity and frequency. The designed PZT energy harvester via flag-flutter mechanism is suitable for energy harvesting in aerospace engineering applications to drive wireless sensors. The maximum output power that can be generated from the designed harvester is 6.72 mW and the optimal resistance is predicted to be 0.33 MΩ

Multi‑disciplinary and multi‑objective optimization of an over‑wing‑nacelle aircraft concept

In this paper a Multi-Disciplinary and Multi-Objective Optimization (MDO-MOO) of a baseline Over-Wing-Nacelle (OWN) concept design is presented. The present study extends previous works, which considered only aerodynamic optimization, to include structural and mission design parameters. The competing objectives of minimum empty weight and minimum fuel weight for a design mission are considered in the multi-objective formulation as well as the single objective problem of minimizing takeoff gross weight, one of many compromises possible for the multi-objective problem. An integrated computational environment has been implemented. High-fidelity analyses for the structural and aeroelastic assessment, together with middle-fidelity analyses for aerodynamic, mission, and performance analyses are performed. A complex multi-disciplinary analysis framework is proposed, in order to account for the interdisciplinary interaction and to provide a consistent computational framework. Optimization results with a Multi Objective Genetic Algorithm (MOGA) show Pareto frontiers accounting for structural, aeroelastic, and mission design constraints. The disciplines coupling is quantified, in terms of constraints, design variables influences, and possible trade-offs among the objectives

Damping modelling in aircraft flutter analyses

The aeronautic industry is moving towards the research for more and more performing materials in order to make the aircrafts increasingly lightweight, and to get a decrease in consumption and atmospheric pollution. These materials result in viscoelastic behavior that is difficult to analyze with traditional structural damping models typically used in design stage. In particular, appropriate description of the damping may become critical for the study of flutter stability margins which may ultimately lead to the initiation of limit-cycle behavior. This paper aims to introduce a first-principle-based viscoelastic damping formulation to be applied to aeroelastic systems describing highly flexible aircraft in order to critically assess its influence into flutter and stability analyses