The continuous growth of global air traffic, the limited availability of oil reserves and the need to reduce the environmental impact of using fossil fuels demand innovative technological solutions to guarantee economic and environmental sustainability of air transport. Sustainability requires, among others endeavors, designing more and more efficient aircrafts, through either a weight reduction (which allows the induced drag to be reduced) or a reduction of the skin-friction drag (the viscous drag that generates when a solid body is in relative motion with a viscous fluid). STREAM intends to attack the problem from both sides, in view of a general reduction of the operating costs for a better environmental and economical sustainability, by improving upon some of the available technological solutions and aiming towards their integration into a functionalized aerodynamic surface.

As far as the skin-friction drag is concerned, it is known that microstructures surfaces equipped with riblets (biomimetic protuberances that can be found on the skin of some fast sharks) are an effective technological solution, which to date still is not used mainly for technological reasons. In fact riblets have a problem with durability of the surface, related to the impact of small particles and dust floating in the atmosphere mainly in the take-off and landing phases. This implies frequent maintenance actions which render the economic budget negative. As far as weight and operating cost are concerned, STREAM targets the two problems of ice formation and accretion on the outer structure of the airplane, and the monitoring of structural health. Ice formation is a critical aspect which carries implications on the aerodynamic efficiency of the external surfaces.

Available solutions to address this problem are based on devices and technologies which not always correspond to the best efficiency in terms of weight, complexity and need for power and energy. Innovative solutions are available in this case too, but technical barriers still prevent their application. Last, monitoring of structural health (SHM) is a further opportunity for improved performance, as it positively impacts on weight and operating costs. Recently proposed technological solutions require further study before reaching application level, and novel technologies could be adopted. Thanks to a well qualified team, STREAM aims at improving existing solutions and at proposing novel strategies towards removal of the key-holes in the abovementioned applications. Moreover, with some ambition, STREAM intends to preliminary address the topic of system integration, which is considered as an opportunity to further increase the solutions’ efficiency through suitable synergies. The advanced technological solutions that emerge would put the aeronautical sector in Campania and in the areas targeted by the PON-MIUR action to achieve and keep competitive advantage. Development of smart technological solutions capable to equip standard structures with technological ingredients to enrich their functionality besides their primary function and to reduce environmental impact as well as operating and maintenance costs would be a break-through for the Italian aeronautical sector. Hence STREAM will focus on the following 3 specific goals:

A) innovative methods for the functionalization of aerodynamic surfaces for drag reduction based on riblets. The project will: design innovative three-dimensional riblets to improve their performance beyond the state of the art; in-depth study the effects of riblets on aircrafts in cruise (e.g. riblets with shock waves); acquire manufacturing capabilities and develop a novel production technology; study and characterize a new concept for riblets deployable on-demand to improve their durability.

B) innovative system for Structural Health Management via the development and set up of specific algorithms to reduce weight, increase operating efficiency, reduction of maintenance times and costs (Condition Based Maintenance)

C) innovative methods for super-hydrophobic and de- and anti-icing surface functionalization, both static and dynamical, based on surface treatment, shape-memory materials and nanotechnology / nanomaterials to provide surfaces with self-cleaning e self-healing properties.

Systems to contrast the icing problem will be studied with weight reduction, based less critical and integrated components. To achieve the whole set of objectives a balanced mix of numerical studies and laboratory experiments will be planned, with RI activities prevailing over SS, to arrive in the final stage at technology demonstrators for systems (A+C) and (B+C), where an innovative SHM will integrate both the other systems.

PURPOSE

The National and European objectives of the air transport can be schematized through the key words of sustainability, efficiency, security, with the utmost priority in seeking benefits for citizens, economy and society as a whole. In parallel, the aeronautical sector must also give an important contribution to the objectives of the COP 21 Paris Agreement implemented within the United Nations (UN) Sustainable Development Goals SDG, resulting in a commitment to reducing pollutants and a general increase in the efficiency and rationalization of the consumption. The international priority challenge is therefore focused on the development of technological solutions to design new, low-impact, resilient aircraft with a view to maintaining safety and cost-effectiveness over time, and with "smart" implementations of new materials, surfaces, profiles, etc.

Within the National Strategic Intelligence Strategy, the Aerospace Area is represented by different development technology trajectories with national priority, where environmental impact reduction is of fundamental importance. This technological trajectory must be pursued through combined and interlaced interventions between national and European initiatives, in collaboration between the public and private sectors.

In this scenario, the search for "smart" solutions, possibly integrated between them, within the Aerospace area is strategic for a number of objectives that can be listed as follows: i) reduce aircraft costs, in terms of investment and use, as well as related to maintenance; (ii) improving performance and reliability of components and systems; iii) develop hybridization and integration solutions of components and systems with traditional and "smart" technology. In this context, the STREAM project is aimed at the development and optimization of advanced technologies, components and systems with "smart" features with priority applications in the field of aircraft functional surfaces. The project's main research lines, integrated with each other, include the study of solutions for the functionalization of aerodynamic surfaces with riblet application, the definition of intelligent algorithms applicable to Structural Health Monitoring solutions, and the development of hydrophobic and de-icing. The project intends to develop the above-mentioned research lines in order to achieve the following goals:

• the identification and development of advanced technological solutions to improve the performance and safety of aeronautical components and systems, with a view to reducing energy consumption and emissions;

• modeling and testing of new functionalized surfaces with integrated capacities (SHM, anti and de-icing, reduction of aerodynamic friction).

Developed technological solutions, components and systems will be experimentally validated by using specific functional demonstrators and integrated solutions that will be specifically designed within the project.

STREAM TEAM

Maurizio Quadrio (DAER)
Giuseppe Sala (DAER)
Alberto Matteo Attilio Guardone (DAER)
Marco Giglio (DMECC)