Aerospace Engineering

Abstract

This chapter summarizes the research activities and main outcomes of the groups engaged in the fields of Aerospace Engineering, in the decade 2013–2023. The research topics are Aerodynamics, Aerospace Systems, Design of Aircraft and Flight, Fluid-dynamics, Propulsion and Structural Technologies.

1 Introduction

Aerospace is, by its name, a multidisciplinary discipline with main roots in flight mechanics, light structures, systems, fluid dynamics and propulsion. The strong interaction is increasing day by day with electronics and materials engineering, as well as electrical and informatics, and including basic sciences like mathematics, numerical simulation and state-of-the-art testing methods.

The birth and development of the Department of Industrial Engineering has offered a unique opportunity for the Aerospace group to interact and develop mutual interests with Colleagues of such a new big department, but also practicing collaborations with other professors nationwide and strengthening those worldwide. Since the beginning of the development of the Department of Industrial Engineering, Aerospace has played a driving role in both research and education aspects and recently also ramping up the activities of the third mission strengthening the collaborations with local companies and with the international big players of the aerospace field. The new department, innovatively called Industrial Engineering, maintained, as requested, separate degree programs, but received the duty of managing those bachelor’s and master’s courses, attempting to achieve efficiencies in staffing and class offerings. From the Ph.D. side, the courses were grouped under the umbrella of Ph.D. in Industrial Engineering, but keeping the specialization in Aerospace.

Another important legacy inherited by the Aerospace group and appreciated by other colleagues has been, and still is, the international activities which have been spread out through the other disciplines. A well-established Erasmus program, together with more than two decades of participation in the Pegasus network have paved the way to new and accredited participation with a driving role for other international activities. The tradition and the vision developed during the years before the birth of the actual department have been transferred and improved inside the new academic system by offering experiences and taking opportunities and vision from other sectors from the viewpoint of reciprocal interest. Colleagues from the aerospace group have been selected and served for the benefit of the Department of Industrial Engineering at any level of involvement. Academic, staff, and functional, research committees have always benefitted from the voluntary positive participation and collaboration of several colleagues always including persons from the aerospace team.

Initial difficulties in practising in a new environment have been identified and smoothed by the assumption of common interests and the understanding of the possibility of moving a step forward thanks to the harmonized participation of all the departmental components. Managing a big group of academics is never an easy job, which may become extremely complex when interacting with career expectations, at any level, which requires a list of priorities, and identifications of weaknesses and strengths. Optimization of infrastructures, exploring best practices, and improving general efficiency is the main goal, and the most important objectives of the leadership managing such a big academic department. The evolution of such leadership, for which the aerospace group are still playing a strong role, passing through the experience and moving toward the strength of the new generation has resulted in a key point in the success of the department, accredited, at the time of writing these pages, as Department of Excellence.

The principal contribution, of course, to the development of the Department of Industrial Engineering should be attributed to its graduates. They have distinguished themselves in many activities, not only in aerospace but also in academia, government institutions and military organizations. The increased rate of success of the department’s graduates is the real figure of a tradition of research and teaching which stresses an appreciation for real applications in an extensive and deep base of fundamentals.

2 Background and Legacy

Aerospace (more properly, Aeronautical) Engineering began at Federico II in 1926, with the establishment of a program in Aircraft Structures by Gen. Prof. Umberto Nobile, appointed Full Professor of that discipline. He was the first Director of the “Gabinetto di Costruzioni Aeronautiche”, which became, over time based on the activities of two of his most famous students, Prof. Luigi G. Napolitano and Prof. Luigi Pascale Langer, respectively, the Aerodynamic Institute and the Aircraft Design Institute.

After a period of difficult interactions among the most representative figures of Aerospace Engineering, with further development of the Gasdynamics Institute, those institutions moved toward the birth of two Departments, one more oriented toward the aeronautics and the other with more space attitude. On January 2007 both these Departments finally converge in the Department of Aerospace Engineering (DIAS). The road to reunification has been long and difficult, but in the end, the entire aerospace sector, including some researchers who belonged to other departments, came together in DIAS, to confirm the common identity, the common aerospace root that originates from the founder of Neapolitan School of Aeronautical and Space Engineering, Prof. Umberto Nobile.

This long and well-established aerospace tradition in addition to favouring and promoting a strong push towards the creation and consolidation of scientific and didactic relationships with national and international universities, in particular through the European PEGASUS network, has given also a significant contribution to the creation of two new degree programs in Aerospace Engineering for the Universities of Southern Italy.

The Second University of Naples, now Università degli Studi della Campania Luigi Vanvitelli, established in 1990, began its activities in the 1991–92 academic year by opening some Degree Courses in Engineering, including that of Aerospace Engineering. A certain number of Professors and Researchers of Federico II moved to this new University and trained in Federico II, enriching the Aerospace Engineering teaching staff of this new University.

In the 2006–07 academic year, the University of Salento in Lecce established the Master’s Degree Course in Aerospace Engineering at the Brindisi branch. The Dean of the Faculty of Engineering asked some professors of Federico II and of the SUN to contribute together with other collaborators and researchers to the birth and development of that Degree Course, created with the aim of supporting the development of the Apulian aerospace industry which in those years had strong growth thanks to the Alenia (Grottaglie and Foggia) and AgustaWestland (Brindisi) plants.

Since the birth of the Department of Industrial Engineering, in 2013, the Aerospace section has contributed to its development by sharing interests, perspectives and development paths with colleagues from other groups, seeking synergies both in terms of sharing scientific topics, but also for the multidisciplinary development of the courses, of the laboratory activities and also of the third mission interactions. The requirements created by the new law, especially in organizational and administrative matters, have also permeated at a scientific level without forcing to reject personal attitudes and traditions, but seeking points of contact such as to improve the efficiency of individuals for the benefit of the entire Department. Virtuous examples have been the collaborations of degree courses, and the introduction of new disciplines (Electrical foundations for aeronautics, just to mention one example) which have proved to be important for the achievement of EASA recognition allowing the students to acquire the theoretical part of the aircraft maintenance qualification.

Another very important aspect of academia is managing people’s careers. The Aerospace Engineering group has contributed to a balanced growth of the entire Department, locating sectors with development needs and harmonizing them with others historically more consolidated, trying, within the limits of what could be allowed, to drive a shared growth of the entire Department. The transparency of these operations has allowed the acceptance of wise planning of career progression by collaborating to smooth out sharp edges and facilitate interpersonal relationships.

The results of these operations, culminating with the award of the Department of Excellence seal, have been experienced and appreciated day after day, in teaching activities, laboratory experimentation and in nationwide and international opportunities that have engaged the people who work in the department, also from an administrative point of view, as evidenced by the number of research programs, by international doctoral activities, by the opening of new collaborations with Italian and foreign institutions.

3 Congresses

The aerospace group has hosted and chaired several conferences in Napoli:

• PSFVIP 10, 10th Pacific Symposium on Flow Visualization and Image Processing, 15–18 June 2015; https://psfvip10.unina.it.

• FLUCOME 2019, 15th International Conference on Fluid Control, Measurements and Visualization, May 27–30, 2019; https://flucome2019.unina.it.

• MEDYNA, 2020: 3rd Euro-Mediterranean Conference on Structural Dynamics and Vibroacoustics; https://medyna2020.sciencesconf.org.

• ISSM9, 2022: 9th International Symposium on Scale Modeling; https://issm9.sciencesconf.org.

• CLEAN AVIATION International Workshop: “Toward Sustainable Transport Aircraft”, 6–7 October 2022.

4 Main Research Groups and Programmes

4.1 Design of Aircraft and Flight Technologies (DAF)

Flight mechanics and flight technologies form a comprehensive field that includes a variety of disciplines, such as aircraft design, stability and control assessment, air vehicle aerodynamics modelling, flight performance prediction, flight dynamics and simulation. The professors and researchers of the flight mechanics field, under the acronym ING-IND/03, bring together the tradition of promoting atmospheric and transatmospheric flight technologies in line with modern research findings, promoting exchange and integration with the most accredited national and international universities, research centers and companies.

The Design of Aircraft and Flight Technologies (DAF) research group is mostly focused on atmospheric flight mechanics and is involved in basic and applied research on the following topics: (i) Aircraft Design and Aircraft MDO, (ii) Digital twin, methods and software for aircraft analysis and design, (iii) Aircraft Aerodynamic Design and Optimization (including propeller design), (iv) Flight Mechanics and Aircraft Performance, (v) Aircraft powertrain optimization and powertrain integration, (vi) Wind Tunnel tests, (vii) Flight Tests, (viii) Flight Simulation.

The DAF research group since 2010 has developed research programmes concerning aircraft design and flight technologies. The research field can be also defined as Flight Physics, which encompasses aircraft aerodynamic design and optimization, flight mechanics and performance, aircraft conceptual and preliminary design, experimental aircraft aerodynamics, flight testing, as well as flight simulation. They are well synchronized and merged bringing the focus on the development of innovative flying vehicles.

The research activities performed by the DAF group in the last 10 years, since the Department foundation, have been focused on the design and development of tools, methods and frameworks for innovative aircraft design and parallel relevant applications on design, optimization and testing (especially aerodynamic testing in the low-speed wind tunnel) of new innovative aircraft configurations. For the last 5–6 years, in particular, the group has been involved in research programmes on hybrid/electric aircraft design, with innovative propulsive powertrain architectures and using fuel cells and Liquid Hydrogen (LH2). The main achievements and the related research topics are summarized in what follows.

The DAF group is very active in applied and financed research projects, especially at the European level and it has a very solid and strict collaboration with many relevant Industries, Universities and Research Centers in Europe, Canada, USA. In the last 10 years, the group has been involved in 2 nationally financed research projects (PON), and in 9 European projects (H2020, Clean Sky, Horizon Europe and Clean Aviation) for a global funding amount of about 5M euro. All research activities are highly applied and in collaboration with industrial partners (Leonardo, Piaggio, Airbus, Tecnam, etc.) for the development of new and innovative products (Fig. 1).

Fig. 1

Research activities within the fields of aircraft design and flight technologies

The DAF researchers have been focusing on the design of innovative and green/low-emissions aircraft with new propulsive systems including batteries, fuel cells and Hydrogen [1, 2]. Also for conventional aircraft configuration, the research developed is focused on global aerodynamic optimization, fuel consumption reduction, weight saving, and higher safety [3, 4]. The activities also involve relevant experimental applications, like the wind-tunnel tests (the group is mainly leading the main subsonic wind-tunnel of the Department for aeronautical applications) and flight tests that are developed at full-scale level (flight tests of light and general aviation aircraft, i.e., in collaboration with Tecnam), but recently also at scaled level (scaled flight testing) with small remotely piloted aircraft [5, 6]. The group has been developing in recent years a lot of methods and software for aircraft design. Some implemented methodologies (for example, a new method for the prediction of directional stability and control derivatives) have been also derived from wind-tunnel tests or deep CFD campaigns [7, 8].

The first aircraft design software developed in the group was ADAS. Next, the DAF group has been focusing on the development of advanced frameworks and tools for aircraft design. The software JPAD developed in Java language [9] represents a mature framework for aircraft design and became also the main commercial product of the spin-off company SmartUp Engineering (www.smartup-engineering.com) established by the group in 2020. The development of an advanced framework [10] has been also pushed by three H2020 and Horizon Europe European projects: AGILE (2015–2018), AGILE 4.0 (2019–2023) and COLOSSUS (2023–2026). The projects aimed at the development of an efficient and fast collaborative framework for aircraft design with a focus on commonality, production, and supply chain. Many applications with some relevant design cases covering regional turboprop aircraft, unmanned vehicles, and commuter seaplanes have been performed during these projects [11]. In the last years, since 2017, the research group has been focusing on developing tools and frameworks for the design of hybrid/electric aircraft configurations. The software HEAD has been developed and several interesting applications have been produced during the EU projects IRON, ELICA, and HERA. During the research project ADORNO (in collaboration with MTU) the group has developed advanced methodologies for engine modelling and production of engine performance tables of modern Very-High BPR advanced turbofan engines.

The research group has also developed tools and methods for the aerodynamic analysis of aircraft and aircraft components. The research has been addressing the design of an efficient flap system for the ATR, the design of the Karman for the ATR aircraft, and the design of winglets for light aircraft and regional transport aircraft. The research group has developed a methodology for wing analysis in non-linear conditions to quickly estimate the high-lift characteristics of wings in clean and flapped configurations. Many CFD-dedicated activities are performed for the analysis and optimization of aircraft. Several automatic tools for the generation of geometries and the automatic optimization of aircraft components have been developed. In 2015–2017 the research group has been working on the use of CFD and wind-tunnel tests for the analysis of several different tail and fuselage configurations to build new advanced design methodologies for the design of innovative turboprop aircraft.

During the last 10 years, the DAF group has been extensively operating the main low-speed wind tunnel facility belonging to the Department of Industrial Engineering. Some relevant applications concerning dedicated research contracts or research projects have been performed. In 2013 there was the wind-tunnel test campaign of the Tecnam P2012 Traveler aircraft. Other recent wind-tunnel experimental activities were dealing with the project IRON (wind-tunnel test of the advanced turboprop configuration with 3 lifting surfaces, including some relevant tests concerning indirect propulsive effects on stability and control). In 2020 There were some relevant and interesting tests of a wing model equipped with 4 electric engines to test the effectiveness of a Distributed Propulsive architecture (DEP). In the project PROSIB we covered also wind-tunnel tests of a commuter configuration. Several interesting tests are ongoing (2023) for the project IMPACT (wind tunnel tests of a rear-end and innovative horizontal tailplane).

Flight simulation is an important discipline where DAF researchers have been active for years. A notable contribution to the field is the ongoing support for the development and maintenance of the widely used open-source flight dynamics model library JSBSim (https://github.com/JSBSim-Team/jsbsim). A line of research on AI-based flight control for fixed-wing aircraft and missiles has been pursued in the past few years. Both consolidated and more recent results in artificial intelligence and Deep Reinforcement Learning (DRL) research have been used—also through joint research agreements with CIRA (Italian Center for Aerospace Research) and MBDA—to design AI-based controllers that make high-performance military aircraft or hypersonic vehicles fully autonomous [12].

4.2 Structural Technologies, Methods and Applications

Structural technologies encompass and integrate a broad range of disciplines, from materials development to analysis, design, testing, manufacturing and maintenance of complete aircraft. Materials and structures have traditionally been the key element enabling progress and major performance improvements in many aerospace systems [13]. The development of the computational power of structures, the improvement of the possibilities of experimentation, research in the sector of intelligent structures together with the evolution of advanced composite materials, now a heritage of daily life, have improved structural performance, reduced operational risks and lowered times of development. In addition to enabling technologies for future aeronautical and space systems, materials and structures continue to be key elements in determining the reliability, performance, testability and cost-effectiveness of these systems [14].

The professors and researchers of the Aerospace Structures field, under the acronym ING-IND/04, bring together the tradition of promoting Aerospace Engineering, and developing the methodologies and applications in line with modern technologies, promoting exchange and integration with the most accredited national and international universities, research centers and companies.

Starting from a common base and to keep pace with the high developments of world research, all researchers in the Aerospace Structures field have diversified and specialized their research interests by creating specific laboratories following a historical strong link between research activities, industrial needs of the aerospace sector and the subjects of the teachings offered to students [15].

The backbone of the study of light aerospace structures is represented by the elasticity of its components which makes the difference compared to other structural disciplines. Rotor blades of a helicopter, wings of a sailplane, and thermoelastic and shock-resistant satellites are just simple examples of the complexity of reaching the efficiency of structural solutions [16]. Aircraft safety has been another important topic developed by the structural aerospace group [17,18,19]. Moreover, in aerospace engineering, the shape is associated with multiple design parameters: aerodynamic efficiency, effectiveness of controls, stability of an aircraft, handling qualities, and so on (Fig. 2).

Fig. 2

Testing the acoustic comfort of a medium-range commercial airplane full-scale fuselage

The structural aerospace topics, inheriting what was already being defined, have been subdivided through mandatory and elective courses and offering all the students the basic principles of the theory of elasticity and methods for solving complex structures while leaving specialized aspects to the elective courses which sometimes are also taken by students of branches different from aerospace. The main idea behind the aerospace structural organization is oriented to transfer approaches that can be used to understand and to analyze the different structural behaviors. The result of such deep knowledge should end up with an efficient structural sizing which enables safety and minimizes the probability of occurrence, during the operational life of any structural element, of any catastrophic event. In a simplified overview, this will be the result of a perfect interaction of theoretical formulations, numerical methodologies and experimental observations which represent the tools for reaching the best fit for complying with assumed structural requirements [20] (Fig. 3).

Fig. 3

Application of guided waves based Structural Health Monitoring (SHM) on a full wing composite upper panel (EU funded SARISTU Research Project). Upper row: sensorised wing panel; middle row: SHM implementation on a skin bay; lower row: Impacted location C-Scan

The aerospace structural team has traditionally spent great interest and reserved strong sensitivity in experimental and laboratory activities [21, 22]. With the development of experimentation technologies, of structural identification algorithms [23, 24], of increasingly sophisticated sensors, they have moved from the use of strain-gauges, still widely used, to the use of MEMS accelerometers, piezoelectric patches, fibers optics, non-contact laser sensors, together with beamforming and non-destructive ultrasound techniques, [25,26,27], for monitoring the health of a structure. The topic of structural health monitoring (SHM) has become an important research line with solid international interactions and continuous participation to the most accredited congresses and strong leadership in international research projects [28, 29]. The use of these, and other, measurement technologies has led to the development of specific skills in the field of structural testing, with the creation of research groups interested in each of these technologies and their integration [30]. By virtue of these interests, and the need for suitable laboratory spaces, some of the group’s activities have been moved to the new Federico II campus in San Giovanni a Teduccio, particularly those related to vibroacoustic testing [31, 32] and researches for passenger comfort [33,34,35,36]. The constant commitment of the members of the structural aerospace group has driven a significant contribution to the growth and development of the activities headed by the San Giovanni campus, also with the organization of international conferences, student activities and the promotion and assessment of relationships and interactions with national and international interested companies.

The list of international projects including persons in the aerospace structural field would be very long, being them participating to the European Framework programs since 1990. Many other research projects have been developed locally or nationwide with close collaboration with other universities and research centers. Moreover, members of the aerospace structural group have been involved in industrial programs, international bodies for setting up certification guidelines, and scientific committees for editing papers, journals and research projects. Just to name a few of them, European funded research project on a competitive basis are CASTLE addressing the well-being of the in-flight passenger, T-WING for the design and manufacturing of the wing of the Next Generation Tilt Rotor (NGTR), SOLIFLY for the basic research on structural batteries. A companion example is also represented by a new book on Structural Dynamics [37], which is going to be published in 2024. All this demonstrates continuity in the group’s activities as well as their importance and international impact with an open view to the future of aircraft transportation [38].

Some specific topics have been addressed during the last decade. They are related to (i) the scaling laws and similitudes for vibroacoustic systems, [39] (an example is in Fig. 4); (ii) the stochastic response of the elastic structure to the turbulent boundary layer (TBL) excitation [40]; (iii) the application of machine learning to the vibroacoustic problems [41]; (iv) the propagation of the elastic waves in structural components [42] (see Fig. 3); (v) the application of the finite element method (FEM), spectral finite element method (SFEM), the wave and finite element method (WFEM) and the statistical energy analysis (SEA) for the vibroacoustics of complex systems [43] (see Fig. 4);

Fig. 4

Acoustic radiated power by two different aluminum plates after having remodulated the response of one over the other: Watt versus Hz

(vi) the analysis and the design of meta-components [44]. (vii) Around these themes a spin-off was also established: https://wavesetconsulting.wordpress.com.

During the years a community (and a series of four symposia) was created around the themes of measurement, modelling, simulation and reproduction of the flow excitation and flow induced structural response (www.flinovia.org, FLow Induced NOise and Vibration Issues and Aspects). These topics are relevant for all the high speed transportation engineering. This community has produced a series of books which represent the evolving state-of-the-art about those topics [45,46,47].

The fourth volume is to appear during 2024 while the fifth symposium was planned in Napoli during the spring of 2026. The previous editions were held in Rome 2013, Penn State 2017, Lyon 2019 and Sydney 2023.

Fig. 5

Rayleigh Benard convection: experimental apparatus and 3D flow field evolution

4.3 Fluid-Dynamics, Aerodynamics and Propulsion

Professors and researchers in the fluid dynamics sector, continuing a long tradition of the University of Naples, have been very active in the last decade in developing methodologies and application in the field of fluid dynamics with particular attention to Aerodynamic (Theoretical and Applied), Aerothermodynamics, Computational Fluid Dynamics, Experimental Thermo-Fluid-Dynamics, Flow control, Fluid dynamic stability, Micro-gravity, Modal analysis and Propulsion. The research activity is organized into five research group.

The Theoretical and Applied Aerodynamic Research Group (TAARG) is involved in both Theoretical and Applied Aerodynamics research fields. Aircraft Aerodynamics, Rotary Wing and Wind Turbine Aerodynamics are the macro contents where the group is performing its main research activity. During last decade TAARG cooperated with many Universities and Research Centers. From the academic side, the cooperation with University of Beijing, San Diego State University and, more recently, Stanford University should be recalled. In addition, TAARG developed joint research programs with CIRA (the Italian Research Center), JAXA (Japan Aerospace Agency) and ONERA (the French Aerospace Labs). It was involved in EU funded Research programs (Clean Sky and Clean Sky 2) and is also active in GARTEUR Projects. During the last ten years visiting researchers coming from China, Japan, France and USA joined the team. Concerning the main scientific activity of the group, it must be cited the fundamental contribution to the development of an Advanced Aerodynamic Force theory which also led to important technology advances in aerodynamic design applications. In particular, the development of a thermodynamic and, more recently, vorticity-based theory [48] allowed for the analysis and decomposition of the Aerodynamic force acting on flying bodies, thus giving the chance of identifying the main physical contributions of the aerodynamic drag (viscous, wave and lift induced), a main concern for the aerodynamic designer. TAARG is world leader in this technology (together with ONERA and Beijing University). The thermodynamic method in particular has been adopted during the design of last generation commercial aircraft. More recently TAARG is dedicating its efforts, together with CIRA, in the still unsolved problem of drag/thrust bookkeeping in steady and unsteady flows. Another important contribution has been given by the understanding of second order effects of riblets. Riblets are streamwise micro-grooves that mimic shark skin and can reduce friction drag in turbulent flows. The models developed by TAARG give now the chance to the scientific community to predict riblet performance on complex aerodynamic surfaces by numerical analyses [49]. The last frontier in which TAARG is now involved is the application of Machine Learning tools in Fluid Dynamics. Together with Stanford University it is focusing on the possibility to adopt Machine Learning in order to finally obtain “exact” virtual aerodynamic, a long time expected results of Computational Fluid Dynamics still far to be reached [50]. Recent activity of the Computational Fluid Dynamics research group has been focused on the design and assessment of robust and accurate numerical methods for both compressible and incompressible flows. As regards incompressible flows, has been developed and tested pseudo-symplectic Runge–Kutta time-integration methods for the incompressible Navier–Stokes equations with applications to the numerical simulation of turbulent flows. In contrast to fully energy-conserving, implicit methods, these are explicit schemes of order p that preserve kinetic energy to order q, with $q>p$. Use of explicit methods with improved energy-conservation properties is appealing for convection-dominated problems, especially in case of direct and large-eddy simulation of turbulent flows [51] (Fig. 6).

Fig. 6

IR 3D temperature map of turbine blades’ ceramic shell mold in industrial environment (METEMI project)

Other contributions are focused on the development of Fast-Projection methods for the discretization of incompressible Navier–Stokes methods. Fast-projection methods are based on the explicit time integration of the semi-discretized Navier–Stokes equations with a Runge–Kutta (RK) method, in which only one Pressure Poisson Equation is solved at each time step. The methods proposed by the group are based on a class of interpolation formulas for the pseudo-pressure computed inside the stages of the RK procedure to enforce the divergence-free constraint on the velocity field. The procedure is independent of the particular multi-stage method and have been applied to some of the most commonly employed RK schemes. As regards compressible flows, the most important contributions [51, 52] have been made in the broad field of structure-preserving numerical methods, with the aim of design robust and accurate methods for turbulent simulations. General conditions for the local and global conservation of primary (mass and momentum) and secondary (kinetic energy) invariants for finite-difference and finite-volume type formulations have been recently derived in a general setting for transport equations relevant to fluid-dynamics problems. This activity completes a systematic analysis of the discrete conservation properties of non-dissipative, central-difference approximations of the convective terms in the compressible flow equations which was previously conducted by the group, and which provides a quite complete characterization of kinetic energy preserving discrete formulations for compressible Euler equations. This analysis has also conducted to novel splittings with exact discrete preservation of kinetic energy. Other recent contributions have been made on the conservation properties of the discretizations of various formulations of the system of compressible Euler equations for shock-free flows, with special focus on the treatment of the energy equation and on the induced discrete equations for other thermodynamic quantities (e.g., entropy) (Fig. 7).

Fig. 7

Numerical simulation of hole-induced dynamics of three-dimensional vertical liquid curtain

The Experimental Thermo-Fluid-Dynamics group (ETFD) undertakes research on a wide variety of fluid flow phenomena, both fundamental and applied, using state-of-the-art experimental methods. The main objectives of fundamental research are the analysis and understanding of the evolution of both transitional and turbulent flows, including boundary layers, jets, swirling flows and natural convection, and hypersonic flows. On the other side, applied research is carried out on the enhancement of the convective heat transfer from different fluidic actuators, such as devices based on synthetic, fractal, swirling and sweeping jets, and flow control of separated flows behind both bluff and aerodynamic geometries. The ETFD group works also in the field of fluid metrology, with focus on the development of Particle Image Velocimetry (PIV) and Infrared (IR) thermography methods. Such advanced techniques are applied via state-of-the-art equipment, including both low-speed and high-speed tomographic PIV systems and cutting-edge IR cameras (high-speed MW and LW cameras). More specifically, in the last decade the ETFD research group has given many substantial contributions to the development of: laser diagnostic techniques as PIV, stereoscopic PIV and tomographic PIV. In particular, it has been co-organizer of the 4th International PIV Challenge https://www.pivchallenge.org/pivchallenge4.html [53]. The tomographic PIV has been applied to a large variety of challenging experiments such as: the study of the three-dimensional organization of the flow structure in a non-reactive model aero engine lean burn injection system, Rayleigh–Benard convection in a cylindrical sample and fractal grid turbulence [54,55,56]; (Fig. 5) Infrared Thermography for 3D surface temperature reconstruction (Fig. 6), heat transfer measurements in fluid flows and transition detection from low-speed to hypersonic flows [57,58,59]; fundamental understanding of jet flows, such as synthetic, swirling, fractal and chevron jets. In general, the free and impinging flow fields and the wall heat transfer distributions have been investigated [60,61,62,63]; technologies for active flow control of wing-tip vortices and bluff bodies wakes [64]. Most of the above scientific research activities are developed within international/national scientific projects: The Advanced Flow Diagnostics for Aeronautical Research (AFDAR); MAteriali e TEcnologie di processo ad alta efficienza per Microfusioni Innovative (MATEMI); Hypersonic Boundary-Layer Transition Prediction, NATO AGARD AVT-RTG; Convective heat Transfer and coherent Structures in Turbulent boundary layers (CONTRAST); High Dynamic Range Measurements in Pipe Flows at High Reynolds Numbers (HIDRA). The ETFD research group has carried out many of its scientific research activities and projects in collaborations with both national and international research institutes, industries and universities, including: Centro Italiano di Ricerche Aerospaziali (IT); Delft University of Technology (The Netherlands); DLR (Germany); Europea Microfusioni Aerospaziali (IT); Imperial Collage (UK); KTH Royal Institute of Technology (Sweden); Lavision GMBH (Germany); Monash University (Australia); Politecnico di Torino (IT); Purdue University (USA); Universidad Carlos III de Madrid (Spain); Universität der Bundeswehr München (Germany); University of Lille (France); University of Twente (The Netherlands) (Fig. 8).

Fig. 8

Left: Technological demonstrator of a nanosatellite propulsion unit. Right: example of tests in arc-jet wind tunnel and rocket propulsion laboratory

The Modal analysis, Stability and Numerical Simulation for Flow Control group is currently active in both theoretical and computational research fields of fluid mechanics stability and flow control as well as numerical simulation in thermo-fluid-dynamics. The group has a consolidated background in theory and methods of hydrodynamic stability and in modal decomposition methods of flow fields (Reduced Order Models with POD, SPOD, DMD techniques). The first focus is on linear stability based on the eigenvalues analysis, applied to the study of shear flows [65] and capillary instabilities of two-phase flows, such as the gravitational liquid curtain subjected to surface tension [66], employed in the technology of coating deposition. Recent research has focused on the experimental characterization of air-water mixing layer flow behind a splitter plate, for atomization processes in combustors. Another research regards the design and application of micro-devices for flow control, i.e., piezo-driven [65, 67] and plasma synthetic jet actuators. A lumped-element physical model to predict the frequency response of both kinds of devices has been developed. The model was validated through experimental tests carried out on home-made devices. Applications have been carried out to control the flow over backward facing ramp, morphing flap, and vertical tail of aircraft. The modal decomposition methods have been used to characterize the spatial and temporal properties of flow fields, extracting both spatial structures and dominant frequencies. The flow control devices have been analyzed by direct numerical simulation and data-driven modal decomposition techniques, with the formulation of Reduced Order Models (ROM) to carry out fast predictions regarding the effectiveness of the control strategies. These techniques have been applied to: two-phase liquid jets; backward facing ramp [67] and curved cylinders [68] piezo-driven and plasma synthetic jets. The numerical simulation work is conducted along three main research directions. The first one is the use of Volume of Fluid (VOF) techniques to complex two-fluid systems. A recent application is the study of 3D vertical liquid jets [69] (Fig. 7). The second topic is relative to the flow through small orifices of particular shaped geometry of thin plates used in the film cooling technology of aeronautic combustors. The third topic regards the simulation of the flow field produced by both piezo-driven and plasma synthetic jet actuators [65], without and with crossflow. Collaborations: University of Princeton, USA; DynFluid Laboratory, Arts et Métiers ParisTech, Paris, France; Harbin Institute of Technology, Shenzhen, China; Rochester Institute of Technology, USA; Delft University of Technology, Delft, The Netherlands; TU Berlin, Germany; University of California San Diego, USA; AVIO AERO GE, Pomigliano; CIRA, Capua; Recent Synergic Research Projects: Distretto Aerospaziale Campano DAC, regional project MISTRAL “Thermal control of a small satellite”, WP 1B-ABBB Thermal Analysis Support, 2015–2020; European Project Clean Sky Air Green, JTI-CS2 CPW1-REG-01-02 “Plasma Synthetic Jet Actuators for High Lift Devices”, 2015–2022; C.I.R.A. contract SHAFT (Synthetic Jet Actuators for flow control) 2017–2020; AVIO AERO GE, contract “CFD Analysis to estimate the sensitivity of the pressure drop, measured through a shaped hole, by a proper pneumatic gauge, as the geometrical parameters are changed”;

The Aerothermodynamics, Propulson and Microgravity research group is devoted to the areas that include access to and re-entry from Space (propulsion and aerothermodynamics), as well as the use of space platforms for experimentation in microgravity. Long-term collaborations are established with national research institutions such as CNR, CIRA (Italian Center for Aerospace Research), with numerous Italian universities (La Sapienza University of Rome, Milan Turin and Bari Polytechnics, University of Padua), large and small companies in the aerospace sector (AVIO, Thales Alenia Space Italia, ALI, T4i, Petroceramics). International collaborations include research projects managed by the Italian (ASI), European (ESA) and American (NASA) Space Agencies and the European Community. International research partners include (DLR, ArianeGroup, Airbus, Trinity College Dublin, University of Birmingham, OHB, Université Libre de Bruxelles. In the field of aerothermodynamics, research is currently aimed at the study of innovative re-entry capsules with variable geometry [70] and new-generation hypersonic aircraft. In particular, a program funded by the Italian Ministry of Defense called Hyperion is in progress on this issue, dedicated to the design of an innovative super/hypersonic aircraft. Research is also carried out aimed at the development of thermal protection systems in ultra-refractory ceramic materials for wing leading edges and for aero-propulsive applications [71,72,73,74]. In this field, a European Horizon 2020 project (C3HARME) was recently concluded, and an ASI project is now underway with CNR, Milan Polytechnic, CIRA and Petroceramics for the aerothermodynamic characterization of ceramic and composite materials for space applications. Among other things, at the Aerothermodynamics laboratory, a hypersonic arc-jet wind tunnel is available for investigations on hypersonic flows and new classes of materials for extreme environments (Fig. 8). In the field of Space Propulsion, the research concerns numerical and experimental studies on the internal ballistics of rocket engines powered by hybrid and monopropellants [75]; experimental developments are possible thanks to the unique laboratory available inside the Military Airport F. Baracca, in Grazzanise (CE). Various research programs are currently in progress on the subject, including research and development projects on paraffin-based fuels funded by the Italian Ministry of Research, and a specific project coordinated by ASI with the participation of all the main Italian private and public players involved in hybrid propulsion. Other national projects (FORCE, RODiO) are dedicated to the development of miniaturized propulsion units for Cubesat applications (Fig. 8).

4.4 Aerospace Systems

With more than 30 years track record of funded projects in aerospace systems technology and applications, the professors and researchers of the Aerospace Systems Team, under the acronym ING-IND/05, develop innovative methodologies and applications in line with the most recent developments in the aerospace systems field. Topics can be grouped in four macro areas:

• GNC technologies for formation flying (FF) and Close-Proximity operations

• Remote sensing systems and solutions

• Unmanned Aircraft Systems and Aeronautics

• Space Awareness

In these areas, Team members lead or participate in competitive research projects promoting cooperation with national and international universities, research centers and companies, as CIRA (Italian Center for Aerospace Research), CNIT (National, Inter-University Consortium for Telecommunications), CNR (National Research Council of Italy), the Italian Air Force (Aeronautical and Space Test Division, Air Force Academy), international universities (University of Stanford USA, University of Colorado, Cranfield University UK, Delft University NL, Universitat Politècnica de Catalunya, Technische Universität Braunschweig, University of Pernambuco), large and small companies (Telespazio, AVIO, Leonardo, MBDA, ST Microelectronics, TIM, Thales Alenia Space Italia, Hitachi, Atitech, Autostrade per l’Italia, Ente Autonomo Volturno, Planetek, D-Orbit), and international entities (AIAA, IEEE, DLR, MITRE Corp., NASA, ONERA, Collins Aerospace, NATO Center for Maritime Research and Experimentation). The group is also actively involved in the organization of top-level International Conferences and Forums such as International Astronautical Congress, AIAA Scitech Forum, IEEE Aerospace Conference, IEEE Metroaerospace Conference (Fig. 9).

Fig. 9

Aerospace systems team areas of interest

Concerning GNC technologies for formation flying and Close-Proximity operations, the Team promote the design, development and experimental/numerical validation of innovative techniques for relative navigation in highly varied mission scenarios, from formation flying to on-orbit servicing (OOS) and active debris removal (ADR). In FF applications, the Team has developed innovative relative positioning techniques based on GNSS data processing, tested with in-flight data, demonstrating real-time centimeter-level relative positioning accuracy. The Team has also developed innovative analytical models for relative motion design, applicable to both FF (e.g., to enable Distributed Synthetic Aperture Radar applications, DSAR) and missions scenarios involving close-proximity operations. Concerning OOS and ADR, which require relative navigation skills with respect to passively cooperative (i.e., equipped with fiducial markers designed to be easily detected and identified within the raw data produced by an electro-optical sensor) and non-cooperative space targets, the Team has developed innovative techniques based on data processing from passive (monocular and stereo cameras) and active (Lidar and Time of Flight cameras) electro-optical (EO) sensors. The above-mentioned techniques have been developed in important projects, as LIDAR-based uncooperative spacecraft relative navigation project (2014–ongoing), funded by Italian Ministry of University and Research (MUR), in which techniques have been tested in cooperation with foreign partners, like Embry Riddle Aeronautical University and Jena Optronik Gmbh; Project GRACC (2020–2022), funded by the European Space Agency (ESA), in which innovative techniques were developed for pose determination and relative state estimation for a satellited equipped with a robotic arm during the reach and capture phases of passively cooperative and non-cooperative targets; Project FORCE (2020–2022), funded by MUR, where a prototype of a relative positioning module compatible with the installation within 1–2 CubeSat-units has been developed and demonstrated in laboratory environment. Most relevant publications in this domain are [76,77,78,79,80,81]. In the field of remote sensing, investigated topics include bistatic and distributed SAR relying on FF satellites, algorithms and techniques for marine and maritime SAR applications, Artificial Intelligence (AI) techniques and solutions for image analysis, within important projects as “Distributed Micro-satellite-based SAR performance study” (2017–2018), commissioned by DSO National Labs, Singapore; “Highly Sensitive Radar Change Detection” (2019–2021), funded by the Italian Ministry of Defense, in cooperation with RaSS-CNIT National Laboratory and Israel Aerospace Industries, aimed at DSAR applications in the field of differential Interferometry; RODiO, an innovative mission funded by the Italian Space Agency (ASI) relying on a cluster of 4 passive CubeSats flying in formation with ASI PLATiNO-1 (PLT-1), aimed at demonstrating space-based DSAR with multi-platform image synthesis; IntSen2, (2023–2025), funded by European Commission, aimed at exploiting Imagery Intelligence (IMINT) in Earth Observation, for the defense and security community; Ueikap, (2023–2025), funded by MUR, aimed at accomplishing several tasks, including the development of a sea imaging model to overcome the existing limitation of the discrimination capability between wake and other natural features, the development of wake imaging model and the definition of a novel AI architecture exploiting suitable datasets based on both archived and simulated data; Mercurio, (2023–2026), funded by Italian Ministry of Enterprises and Made in Italy, aimed at monitoring railway infrastructure, exploiting AI and fusion of satellite data, distributed sensors, and aerial inspections. Most relevant publications in this domain are [82,83,84,85,86,87,88,89,90] .

In the Unmanned Aircraft System (UAS) and Aeronautics domain, numerical and experimental activities are carried out in synergy at the Laboratory for Innovative Flight Technologies (LIFT), located in San Giovanni a Teduccio, and at the Guidance Navigation and Control (GNC) Lab, located in Naples.

With the theoretical and experimental activities carried out at LIFT, the team contributes to CeSMA (the Federico II Center for Advanced Metrological and Technological Services). LIFT is ENAC recognized drone operator with a netted area for safe outdoor operation, at the CeSMA location in San Giovanni a Teduccio, and a reserved volume of Low-Level airspace, under a NOTAM issued by ENAC, at the Pilot Farm of Castel Volturno of the Federico II Department of Agricultural Sciences. The laboratory is a full member of the Association for Scientific Development of Air Traffic Management in Europe ASDA (asda.aero) sponsored by SESAR joint undertaking. The main activities carried out at LIFT concern innovative solutions for Small (100–150 kg MTOW) fixed-wing UAS systems (projects GANNET, for innovative MEMS based inertial navigation avionics, and project DAPHNE, for full-electric hydrogen-fuel-cell on board power generation UAV platform for low-impact environmental monitoring, both funded by the Italian Ministry of Industry and Made in Italy); innovative sensing configurations including Machine-Learning-based solutions for aerospace; Air-Data-System integrity check; Bio-inspired navigation technique exploiting the skylight polarization; characterization of radar observation of multi-rotor drones for detection and identification, as well as for countermeasures in cooperation with Air Division of Aeronautical and Space Experimentation of Italian Air Force (Project CUTE LAB); payloads and procedures for drones (e.g., projects FOCUS and COVID-19, funded by Regione Campania); development of innovative tools for risk analysis of airport routes in cooperation with Toscana Aeroporti; solutions for exploiting the innovative 5G mobile communication network for application of navigation, surveillance, TLC and TLM, remote piloting, traffic management of drones, in challenging conditions, in cooperation with TIM. Most relevant publications in this domain are [91,92,93,94,95,96]. Concerning the GNC Lab, UAS-related research involves several interconnected topics, ranging from multi-drone operations and cooperative techniques, to path planning with emphasis on Urban and Advanced Aerial Mobility frameworks, sense and avoid and airspace surveillance, multi-sensor-based navigation and highly autonomous approach and landing. These research paths are followed for civilian and defense applications in collaboration with national and international partners including NASA, ASI, Collins Aerospace, Raytheon, MBDA, Civitanavi Systems, and local SME. Main activities and projects conducted at GNC Lab are: CREATEFORUAS (2019–2023) and 4IPLAY (2023–2025), both funded by MIUR, with a focus on multi-drone cooperation, sense and avoid technologies and swarming techniques for infrastructure inspection; AMPERE (2020–2022), funded by EUSPA within the Horizon 2020 Programme, aimed at dedicated solutions for electrical power network information gathering; SKYNET (2022–2023) and EVOLVE (2021–2024), in collaboration with Collins Aerospace, aimed at low altitude airspace surveillance with ground-based radars and at extending to highly autonomous UAM/AAM frameworks the enhanced sensing technologies and algorithms adopted for low visibility approach and landing; HISENSE (2023–2025), in collaboration with Civitanavi Systems under funding of the Ministry for Economic Development, concerning architectures and algorithms to fuse exteroceptive and inertial sensors information for safety critical applications. Most relevant publications in this domain are [97,98,99].

In the Space Awareness domain, innovative methods and solutions are developed within a dual use framework, including both Space Traffic Management and Space Situational Awareness for security and defense. Recent developments include ad hoc models for in orbit fragmentation and medium term collision risk assessment, machine learning-based approaches for resident space object characterization, algorithms for light curve inversion and rotational state determination, agile multi-satellite maneuvering logics for responsive Earth observation. The main projects are: INTEGRAL (2021–2024), funded by the European Defense Agency and carried out in cooperation with the most important European SSA industries, under coordination by Leonardo; ISTAR (2023–2026), research project funded by ASI, concerning various machine learning-techniques and integrated approaches with emphasis on fragmentation, space object characterization, space-based SSA, sensor tasking, and cooperative approaches to Space Traffic Management; IHS (2023–2026), funded by ASI, to realize the Italian civilian infrastructure for SSA/STM, concerning fragmentation and SSA services related to In-Orbit Servicing missions.

5 Future

The aerospace sector’s future is brimming with thrilling prospects. These encompass both low-velocity, low-atmosphere flight and high-speed transportation in space, all underpinned by a shared commitment to environmental sustainability and respect for our planet for future generations. Military applications have also received a boost in the research and development from the actual international scenario, but a specific interest is outside the scope of this review.

All the research groups of the aerospace community of the Department of Industrial Engineering are strongly involved in such mid/long-term research and development following a multidisciplinary approach not only among the classical aerospace disciplines but including many others and not necessarily from the engineering side, but including biosciences, medicine, agronomy and so on. Specific research lines for the next decade are driven by the decarbonization expected to reach the goal of zero CO${}_2$ by 2050. According to this objective set by the European Commission, the studies of hybrid-electric and full electric airplane will be continued, passing from the use of SAF (Sustainable Aviation Fuel) and hopefully arriving to the hydrogen engine. Meantime the application of the electric propulsion will drive the urban air mobility systems, from small drone to people transportation, which are expected to become normal by the end of this decade. A long list of potential applications is under study in this field. The supersonic and eventually the hypersonic transportation are expected to play an important role, driven by the space transportation activities and by the space tourism activities, which is almost a mature reality.

Space exploration and human settlement on the Moon and on the planet Mars are a challenge which will involve all the scientific community for the next years and, again, the aerospace group of the department has numerous and highly accredited worldwide collaborations.

These activities will also have a direct relationship with the courses offered to the students. The aerospace syllabus has always shown great flexibility, incorporating knowledge from other colleagues, as in the electrical field or for the risk management course, and exporting also courses toward other disciplines. By virtue of this attitude, we can easily forecast an increase of the international contacts with other universities by increasing the students’ exchange programs and the number of double degree collaborations. The ability and the recognition of the professors of the aerospace sector in dealing with research institutions and the industrial world will speed-up the third-mission activities, with the support of spin-off companies, student associations and contests.

To be awarded with the seal of Department of Excellence has been an honor, but also a responsibility and the attitude of the aerospace group is to consider the honor for what it has been, and a responsibility for what it will be.

6 Awards

Best Paper by young researcher, 2015 IEEE Metrology for Aerospace—“Large space debris pose acquisition in close-proximity operations” by Opromolla, R. et al.

Yasuki Nakayama Medal, 14th International Conference on Fluid Control, Measurements and Visualization (FLUCOME 2017)—For Keynote speech “Thermo-fluid-dynamic analysis of innovative synthetic jet devices” by Carlo Salvatore Greco, Gerardo Paolillo and Gennaro Cardone. 2017 IOP Conf. Ser.: Mater. Sci. Eng. 249 011001.

ICAS Award for Innovation in Aeronautics, 2018—Awarded to the AGILE Consortium for outstanding and innovative contributions to the development of advanced aeronautical systems. 31st ICAS (International Council of Aeronauticakl Sciences) Congress, September 9–14, 2018, Belo Horizonte, Brazil.

Best Paper Award, 2019 AIDAA XXV International Congress—Awarded by AIDAA (Italian Association of Aeronautics and Astronautics) to the article by Di Martino G. D., Gallo G., Mungiguerra S., Carmicino C., and Savino R., “Modelling of Paraffin-based Fuel Combustion in Hybrid Rockets”, AIDAA XXV International Congress of Aeronautics and Astronautics, Rome, Italy, September 2019.

Leonardo da Vinci Award 2019—In 2019 the DII participated to the Leonardo da Vinci announcement, a MAECI-MIUR framework 2017/2020 funded by CRUI and MUR, proposing as unique candidature Giuseppe Petrone, young researcher belonging to Aerospace Structures field (ING-IND/04), for the task 2 “Mobility of young researchers”. Dr. Petrone was one of the winners (Proposal ID 158152) and this award gave him the possibility to spend time at Universidad de Chile to conduct some joint research activities.

Measurement Science and Technology’s Outstanding Paper Award for 2021 in the field of Fluid mechanics—“On the PIV/PTV uncertainty related to calibration of camera systems with refractive surfaces” by Gerardo Paolillo and Tommaso Astarita, 2021 Meas. Sci. Technol. 32, 094006. DOI 10.1088/1361-6501/abf3fc.

Featured by Physics of Fluids—Article: “Receptivity to forcing disturbances in subcritical liquid sheet flows” by Alessandro Della Pia et al. (2021), Physics of Fluids, 33 (3), art. 032113, DOI: 10.1063/5.0044322.

Featured by Physics of Fluids—Article: “Modal decomposition analysis of unsteady viscous liquid sheet flows” by Antonio Colanera et al. (2021), Physics of Fluids, 33 (9), 092117, DOI: 10.1063/5.0065683.

Best Paper, 2022 AIAA Sensor Systems and Information Fusion—“Using Drone Swarms as Countermeasure of Radar Detection” by Claudia Conte et al., AIAA 2022-0855.

Best Paper, 2023 IEEE Metrology for AeroSpace (MetroAeroSpace)—“Experimental Assessment of a Visual-Laser Relative Navigation Module for CubeSats” by G. Napolano, et al.

Fulbright fellowship—“SPOD and reduced order modeling of separated flows (SPARROW),” carried out at the Princeton University, under the cooperation of professors H. Stone, F. Grasso, and M. Hultmark, from 01/05/2023 to 31/08/2023.