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Variable camber wing technology stands out as the most promising morphing technology currently available in green aviation. Despite the ongoing advancements in smart materials and compliant structures, they still fall short in terms of driving force, power, and speed, rendering mechanical structures based on kinematics the preferred choice for large long-range civilian aircraft. In line with this principle, this paper introduces a linkage-based variable camber trailing edge design approach. Covering coordinated design, internal skeleton design, flexible skin design, and drive structure design, the method leverages a two-dimensional supercritical airfoil to craft a seamless, continuous two-dimensional wing full-size variable camber trailing edge structure, boasting a 2.7 m span and 4.3 m chord. Given the significant changes in aerodynamic load direction, ground tests under cruise load utilize a tracking-loading system based on tape and lever. Results indicate that the designed single-degree-of-freedom Watt I mechanism and Stephenson III drive mechanism adeptly accommodate the slender trailing edge of the supercritical airfoil. Under a maximum cruise vertical aerodynamic load of 17,072 N, the structure meets strength requirements when deflected to 5°. The research in this paper can provide some insights into the engineering design of variable camber wings. [ABSTRACT FROM AUTHOR]

There are flapping wing-style systems being developed by various institutions around the world. However, despite there being many systems that superficially appear robust, there is no viable flapping wing flying system at this time. We identified a gap in knowledge and capability, which is that the lack of appropriate instrumentation seems to be a major roadblock in further developing flapping wing flying systems. There is no complete solution in regards to instrumentation and sensing at the appropriate scales. This paper seeks to critically examine and classify the existing instrumentation utilized and reported in the literature and attempts to identify the path forward for flapping wing-style instrumentation. [ABSTRACT FROM AUTHOR]

Purpose: Endurance time is an important factor limiting the progress of flapping-wing aircraft. In this study, this paper developed a prototype of a double-wing flapping-wing micro air vehicle (FMAV) that mimics insect-scale flapping wing for flight. Besides, novel methods for optimal selection of motor, wing length and battery to achieve prolonged endurance are proposed. The purpose of this study is increasing the flight time of double-wing FMAV by optimizing the flapping mechanism, wings, power sources, and energy sources. Design/methodology/approach: The 20.4 g FMAV prototype with wingspan of 21.5 cm used an incomplete gear flapping wing mechanism. The motor parameters related to the lift-to-power ratio of the prototype were first identified and analyzed, then theoretical analysis was conducted to analyze the impact of wing length and flapping frequency on the lift-to-power ratio, followed by practical testing to validate the theoretical findings. After that, analysis and testing examined the impact of battery energy density and efficiency on endurance. Finally, the prototype's endurance duration was calculated and tested. Findings: The incomplete gear facilitated 180° symmetric flapping. The motor torque constant showed a positive correlation with the prototype's lift-to-power ratio. It was also found that the prototype achieved the best lift-to-power ratio when using 100 mm wings. Originality/value: A gear-driven flapping mechanism was designed, capable of smoothly achieving 180° symmetric flapping. Besides, factors affecting long-duration flight – motor, wings and battery – were identified and a theoretical flight duration analysis method was developed. The experimental result proves that the FMAV could achieve the longest hovering time of 705 s, outperforming other existing research on double-wing FMAV for improving endurance. [ABSTRACT FROM AUTHOR]

This paper introduces three new gust load alleviation control strategies, which are based on variable camber technology, to achieve the design requirements for the safety, economy, and comfort of modern civil aircraft. These strategies involve adjusting the inner and outer flap differential of wings, spoilers, and ailerons to alter the aerodynamic shape of the aircraft structure, resulting in drag reduction and gust load alleviation during stepped cruise flights. Furthermore, a logic design is provided for both the cruise drag reduction function and the gust load alleviation function. To validate the effectiveness of the proposed gust load alleviation control strategies, simulation results are presented, utilizing ride quality and wing root bending moment changes as the evaluation criteria. The presented approaches ultimately lead to the development of an optimal scheme that meets the desired design requirements. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a structural sizing approach of an unmanned aerial vehicle (UAV) wing that takes into account the aeroelasticity effects through a fluid–structure interaction analysis. Design/methodology/approach: The sizing approach proposed in this study is an iterative process, each iteration of which consists of two sub-loops, a multidisciplinary analysis (MDA) loop followed by a structural optimization loop. The MDA loop seeks the aeroelastic equilibrium between aerodynamic forces and structural displacements using a fixed-point iteration scheme. Once the equilibrium is reached, the converged pressure loads are used for the structural optimization, which aims to find the structural thicknesses that minimize the wing weight under failure criteria. The two sub-loops are run sequentially in an iterative process until the mass is converged. The analysis models are implemented in open-source software, namely, PANUKL for aerodynamics and MYSTRAN for structures, while the whole process is automated with Python and integrated in the open-source optimization framework OpenMDAO. Findings: The approach was applied to the design of the Predator MQ-1 wing. The results of the MDAs show the convergence of the wing deformations to the flight shape after few iterations. At the end of the aeroelastic sizing loop, the result is a structurally sized wing with minimal weight considering the aeroelasticity effects. Originality/value: The approach proposed takes into account the wing aero-structural coupling effects while sizing its structure instead of a fixed load distribution. In addition, the approach is fully based on open-source codes, which are freely available for public use and can be fully reproducible. [ABSTRACT FROM AUTHOR]

Within the double-sided countersunk riveting process of aircraft wings with a composite wedge structure, riveting consistency is poor, and composite damage is severe, which seriously affects the performance and reliability of the aircraft structure. This paper used the principal stress method to establish a stress model of countersunk riveting, and, based on the analysis of the stress on the structure during the pressure-riveting process, a composite structure rivet was designed. A finite element simulation model of the double-sided countersunk riveting of composite wedge structures' composite rivets was established. The influences of the structure and the matching parameters of composite rivets on both the plastic flow of pressure riveting and the compressive stress of the structure during the pressure-riveting process were analyzed. The structural parameters and riveting process of composite rivets were optimized. The results show that the composite rivet structure could significantly reduce the contact-compressive stress at the riveting joint by more than 20%, thereby reducing the damage caused by the riveting to the composite material. For 4 mm rivets, an aperture of 4.04~4.06 mm can achieve precise relative interference riveting at 0.6% to 1.0%. Employing a 2.6 mm rivet elongation can exactly fill the countersunk hole of the wedge. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to assess the feasibility of additively manufactured wind tunnel models. The additively manufactured model was used to validate a computational framework allowing the evaluation of the performance of five wing models. Design/methodology/approach: An optimized fighter wing was additively manufactured and tested in a low-speed wind tunnel to obtain the aerodynamic coefficients and deflections at different speeds and angles of attack. The flexible wing model with optimized curvilinear spars and ribs was used to validate a finite element framework that was used to study the aeroelastic performance of five wing models. As a computationally efficient optimization method, homogenization-based topology optimization was used to generate four different lattice internal structures for the wing in this study. The efficiency of the spline-based optimization used for the spar-rib model and the lattice-based optimization used for the other four wings were compared. Findings: The aerodynamic loads and displacements obtained experimentally and computationally were in good agreement, proving that additive manufacture can be used to create complex accurate models. The study also shows the efficiency of the homogenization-based topology optimization framework in generating designs with superior stiffness. Originality/value: To the best of the authors' knowledge, this is the first time a wing model with curvilinear spars and ribs was additively manufactured as a single piece and tested in a wind tunnel. This research also demonstrates the efficiency of homogenization-based topology optimization in generating enhanced models of different complexity. [ABSTRACT FROM AUTHOR]

In this paper, a numerical analysis of a biomimetic unmanned aerial vehicle (UAV) is presented. Its wings feature three grids at the tip similar to the primary feathers of birds in order to modify the lift distribution over the wing and help in reducing the induced drag. Numerical analysis using computational fluid dynamics (CFD) is presented to analyze the aerodynamic effects of the changes in dihedral and angle of attack (with respect of the rest of the wing) of these small grids at the tip. The aerodynamic performances (lift, drag, and efficiency) and rolling capabilities are obtained under different flight conditions. The effects of changing the dihedral are small. However, the change in the grid angle of attack increases aerodynamic efficiency by up to 2.5 times when the UAV is under cruise flight conditions. Changes to the angle of attack of the grids also provide increased capabilities for rolling. Finally, boundary values of the pressure coefficient and non-dimensional velocity contours are presented on the surfaces of the UAV, in order to relate the aerodynamic results to the aerodynamic patterns observed over the wing. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this research paper is to recover the autonomous flight performance of a mini unmanned aerial vehicle (UAV) via stochastically optimizing the wing over certain parameters (i.e. wing taper ratio and wing aspect ratio) while there are lower and upper constraints on these redesign parameters. Design/methodology/approach: A mini UAV is produced in the Iskenderun Technical University (ISTE) Unmanned Aerial Vehicle Laboratory. Its complete wing can vary passively before the flight with respect to the result of the stochastic redesign of the wing while maximizing autonomous flight performance. Flight control system (FCS) parameters (i.e. gains of longitudinal and lateral proportional-integral-derivative controllers) and wing redesign parameters mentioned before are simultaneously designed to maximize autonomous flight performance index using a certain stochastic optimization strategy named as simultaneous perturbation stochastic approximation (SPSA). Found results are used while composing UAV flight simulations. Findings: Using stochastic redesign of mini UAV and simultaneously designing mini ISTE UAV over previously mentioned wing parameters and FCS, it obtained a maximum UAV autonomous flight performance. Research limitations/implications: Permission of the directorate general of civil aviation in the Republic of Türkiye is essential for real-time UAV autonomous flights. Practical implications: Stochastic redesign of mini UAV and simultaneously designing mini ISTE UAV wing parameters and FCS approach is very useful for improving any mini UAV autonomous flight performance cost index. Social implications: Stochastic redesign of mini UAV and simultaneously designing mini ISTE UAV wing parameters and FCS approach succeeds confidence, highly improved autonomous flight performance cost index and easy service demands of mini UAV operators. Originality/value: Creating a new approach to recover autonomous flight performance cost index (e.g. satisfying less settling time and less rise time, less overshoot during flight trajectory tracking) of a mini UAV and composing a novel procedure performing simultaneous mini UAV having passively morphing wing over certain parameters while there are upper and lower constraints and FCS design idea. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of the chordwise fence on the spanwise change in aerodynamic characteristics of an aircraft wing with a different taper ratio for varying angles of attack. The investigation was carried out for the tapered wing with different taper ratios of 0.41, 0.6, and 0.75. The wing is tested in a subsonic, low turbulence wind tunnel at the free stream Reynolds number of 2.3×105 for various angles of attack ranging from α = 0° to 45°. The baseline wing model is attached to a fence of different diameters of 1.5 and 2.5 mm at a plane equal to the root and tip chord. There are pressure ports spread across the span of the wing, and the corresponding surface pressure is measured using the MPS 4264 miniature pressure scanner. The surface pressure measured is analyzed further for the variation of the aerodynamic characteristics of the wing. The presence of a fence on the tapered wing forms an efficient flow control device that delays the flow separation, thereby delaying stall angles and preventing the steep transition of the favorable pressure gradient to the adverse pressure gradient at the stall. The presence of a fence on the wing surface has considerably increased the lift coefficient, and the stall is significantly delayed for a least taper ratio wing. The fence has suppressed the interaction of the leading-edge vortices with the tip vortices; thereby, the spanwise flow from the root chord to the tip chord is controlled. [ABSTRACT FROM AUTHOR]

The occurrence of probabilistic common cause errors (PCCEs) in man‐machine systems can lead to multiple human errors being affected by common causes and will contribute greatly to the reliability of the system. In this paper, A reliability modeling method based on event tree (ET)‐fault tree (FT) model for man‐machine systems subjected to PCCEs is proposed. Under the influence of PCCEs, risk factors in the system are not independent, and human errors affected by the same common cause will occur with different probabilities. To describe the dependencies among risk factors, a PCCE gate is proposed to extend FTs in the ET‐FT model. To analyze the impact of common causes on the human error probabilities and quantify the extended FT, an explicit method and an implicit method based on the Cognitive Reliability and Error Analysis Method are proposed. The proposed quantification methods consider the different relationships among multiple common causes in a single model. Finally, the proposed methods are validated in the reliability assessment of the emergency response system under malfunction of the solar wing mechanism. [ABSTRACT FROM AUTHOR]

As the population of the world's major cities increases, urban ground transportation capability reaches its limits. Consequently, electric vertical takeoff and landing aircraft have been developed to address this issue. Modern vertical takeoff and landing designs vary in configurations, each possessing distinct aerodynamic properties. In this work, we focus on the interaction between rotors and fixed wings in a parallel layout, using a prototype with an unconventional configuration as an example. The interaction between the slipstream of rotors and the wake of fixed wings is analyzed using the vortex particle method. Actuator surface model is used to deal with the boundary problem between the wing and the rotors. The applicability of the simulation method adopted in this paper is verified through experimental tests on the thrust and torque of the rotors. The results indicate that under the condition of forward flight at zero angle of attack, the existence of rotor slipstream induces a significant increase by three to four times the local lift on the wing. Correspondingly, under vertical takeoff and hovering conditions, the existence of the rotor slipstream causes the local effective velocity and circulation of the wing to increase. On the other hand, at zero angle of attack and a forward flight, the lift coefficient of the rear rotors increases slightly due to the presence of the wing wake. The lift distribution of the rear rotors along the radial direction also changes greatly. [ABSTRACT FROM AUTHOR]

This paper studies static test methods and test loads of Carbon Fiber Reinforced Polymer (CFRP) wing-box, analyzes the test results, and compares the test results of T800 CFRP wing-box from HENGSHEN Co., LTD and TORAY. It comes out that the stiffness of the T800 CFRP wing-box from HENGSHEN is equivalent with that of TORAY, while the strength meets the structural design requirements, which can be applied on the scheduled aircraft structure for further verification. [ABSTRACT FROM AUTHOR]

Tidal intrusion fronts are surface convergences that occur at constrictions in estuaries during the flood tide, separating incoming higher‐salinity water from lower‐salinity, stratified estuarine water. Previous observations of tidal intrusion fronts describe a V‐shaped planform, with the apex of the V pointing into the estuary, however the significance of this structure has not been previously explained. Observations near the mouth of the James River estuary during the flood tide reveal the development of a quasi‐steady, V‐shaped front. Considering a reference frame oriented normal to the front, the velocity and density structure are consistent with gravity‐current dynamics, but the oblique orientation of the front relative to the impinging flow indicates strong, along‐front shear, which results from vorticity produced by flow separation at the lateral boundaries as well as topographic torque from upstream. The combination of convergence and along‐front shear leads to enhanced mixing, as revealed by acoustic backscatter images of shear instability and persistent subcritical gradient Richardson number in the frontal zone. Oblique fronts such as this tidal intrusion front are common features of estuaries, and they play an important role in vertical exchange due to subduction and mixing of surface water. Plain Language Summary: Surface fronts are among the most notable features of estuarine and coastal environments. They have important consequences for the physics as well as the biology, due to the strong gradients, aggregation of particles and organisms, and mixing that occur at fronts. One of the most conspicuous types of estuarine fronts is the tidal intrusion front, which forms near the mouth during the incoming tide and usually exhibits a V shape pointing into the estuary. This study explains the processes responsible for the V‐shaped configuration of the front and their implications. The density contrast across the front is one important ingredient of the dynamics, resulting in a strong convergence of surface flow. The other key ingredient is the shear across the front, with faster inflow on the inside of the V and weaker flow on the outside. This shear is due in large part to "flow separation" at the sides of the estuary—the same process that causes stall of airplane wings or the formation of eddies behind rocks at the edges of a stream. The paper shows that this combination of processes leads to strong mixing in the frontal zone—much stronger than would occur in the absence of the cross‐front shear. Key Points: The "V"‐shaped tidal intrusion front exhibits a combination of density‐driven, convergent flow and along‐front shear resulting from lateral flow separationThe along‐estuary flow at the front is supercritical (with respect to gravity current propagation), but the velocity in the front‐normal direction is criticalThe along‐front shear significantly augments vertical mixing within the frontal zone relative to the mixing in normal gravity currents [ABSTRACT FROM AUTHOR]

There are complex coupling relationships between flight motion and energy management for hybrid electric fixed wing UAVs with photovoltaic/fuel cell/battery. Aiming at realizing high-energy-efficiency long endurance autonomous flight, this paper proposes a coordinated optimization method of trajectory optimization and energy management for hybrid electric UAVs. Numerical simulation and experiment are carried out. Separated by surplus demand energy except that produced by PV, this method includes an optimal energy flight trajectory optimization layer and an energy management layer. For the former, fuzzy neural network sequential convex optimization (FNNSCP) is proposed to handle the flight trajectory optimization problem for maximizing utilization solar energy. For the latter, an online energy management strategy based on convex quadratic programming MPC (CQPMPC) is proposed to realize the power allocation. Numerical simulation results show that FNNSCP reduced 2% energy requirement compared with Radau pseudo-spectral method (RPM) from flight trajectory optimization level. From energy management level, CQPMPC saves hydrogen consumption by 3.1% and 16.3% compared with nonlinear model predictive control (NMPC) and fuzzy logic state machine (FLSM), respectively. In the experiment, less hydrogen fuel is consumed by proposed method by 5.2% and 15.6% compared with NMPC and FLSM, respectively. Experimental results show that the proposed method has better energy-saving performance and excellent real time performance. It indicates that optimizing flight trajectory and improving energy management efficiency can realize the high-energy-efficiency flight of hybrid electric UAVs. This method is conducive to promoting the application of hydrogen energy in the field of UAVs. [Display omitted] • A coordinated optimization method is proposed for the high-energy-efficiency flight. • Fuzzy neural network adaptive sequential convex optimization method is proposed. • Online energy management strategy with convex quadratic programming MPC is proposed. • The proposed method is verified by simulation and energy management experiment. [ABSTRACT FROM AUTHOR]

Aircraft employing the boost-glide-cruise combination flight mode can achieve longer range, but traditional single configurations struggle to achieve good aerodynamic performance. This paper introduces a novel design method for a combined two-stage waverider, aiming to enhance aerodynamic performance while considering the integration of different engines. After completing the boosting and gliding phases, the lower surface and engines of the first-stage waverider are discarded to promptly reduce aircraft weight, allowing for improved aerodynamic performance and more efficient propulsion during the cruising phase. The airbreathing cruising waverider is designed based on the principle of osculating cone at a fixed Mach number, combining the waverider forebody, afterbody, and stretched body to obtain a complete waverider configuration, equipped with a scramjet engine. The flow field corresponding to the wide-speed-range gliding waverider is reverse-designed using the upper surface of the airbreathing waverider, allocating different Mach numbers and shock angles for the conical flow field, obtaining the wide-speed-range waverider configuration through streamline tracing, and equipping it with a rocket engine. The two waveriders are combined by sharing the upper surface, while constraints on the inlet cross-section are provided to ensure no intersection or overlap of the lower surfaces. Subsequently, numerical simulations were conducted to analyze the aerodynamic performance of the two-stage waverider, verifying the validity of the design method. Finally, the configuration was applied to a boost-glide-cruise flight trajectory, revealing that the two-stage waverider designed in this paper is highly suitable for long-distance flight. Compared with a single-stage wide-speed-range gliding waverider with the same configuration, the range is increased by 147.8 %, further validating the rationality of the design method presented in this paper. • A separable two-stage waverider design based on boost-glide-cruise combined trajectories is proposed. • A wide-speed-range waverider and a fixed Mach number airbreathing waverider are employed to optimize performance. • It achieves a significant range increase in the cruising phase than the single-stage waverider. [ABSTRACT FROM AUTHOR]

This paper examines a Distributed Propulsion (DP) concept and involves CFD verification, optimisation and evaluation. The first part of the study validates the employed simulation methods using experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the Folding Conformal High Lift Propeller (HLP) project, for isolated and installed cases under various conditions. Additionally, validation for rotor-rotor interactions was also conducted using the GARTEUR Action Group 26 measurements. The second part of the paper examines installed propeller configurations to identify performance differences based on their position relative to a lifting wing. The results indicate that distributed propellers with small radii interfere more with the wing, than tip-mounted, large propellers. Additionally, propeller and wing performance vary with respect to the propeller installation location. The propeller in tractor configuration showed higher efficiency than the over-the-wing (OTW) configuration by about 7%. However, results from this work showed a 2% improvement in the propeller efficiency when the OTW configuration had a pylon installed. This study also found that optimising the propeller from a tractor to OTW configuration, significantly improved the wing performance. At take-off and landing, the Lift-to-Drag (L/D) ratio of the OTW configuration almost quadrupled, and the overall propulsive efficiency increased by about 5%. The simulations showed that the OTW configuration with different numbers of propellers, outperformed the tractor configurations with the same number of propellers. Furthermore, up to 26% improvement in lift and overall propulsive efficiency was found by introducing the DP system in the OTW configuration. [ABSTRACT FROM AUTHOR]

In response to escalating environmental concerns and stringent economic constraints, there is an urgent need to develop aircraft technologies and configurations that substantially enhance efficiency. A prominent trend in aircraft design aimed at minimizing lift-induced drag, improving fuel efficiency, and mitigating emissions is the adoption of increased wing Aspect Ratio (AR). This paper examines the evolution and current advancements in High Aspect Ratio Wing (HARW) and Ultra-High Aspect Ratio Wing (UHARW) configurations for next-generation transport aircraft. Beginning with a historical overview of wing AR in transport, the paper examines the progress in designing both conventional and novel HARW/UHARW configurations. It reviews a range of promising concepts, such as strut-braced wing, truss-braced wing, twin-fuselage, and folding wingtips, for their potential in HARW applications. The paper emphasizes tailored conceptual design methods and tools specifically developed for HARW/UHARW configurations. It provides an in-depth analysis of preliminary design approaches for HARW aircraft, systematically covering aspects including aerodynamic, aeroelastic, aerostructural, and experimental designs. Key insights from leading-edge research are distilled, highlighting the significant advancements and pinpointing the current challenges in the field. The comprehensive review underscores the critical role of HARW/UHARW in enhancing aircraft performance, particularly in fuel efficiency and environmental impact, setting the stage for future transformative developments in aircraft efficiency. [ABSTRACT FROM AUTHOR]

• Chaotic snap-through phenomena are studies for bistable cantilever shell. • Transverse foundation excitation subjects to fixed end of bistable cantilever shell. • Analytical results of frequency-amplitude and force-amplitude responses are obtained. • Chaotic, quasi-periodic and snap-through vibrations are presented for bistable shell.5. Vibration experiment is carried out to investigate dynamic snap-though behaviors. The realization of the dynamic snap-through behaviors provides the new design ideas in the fields of the morphing aircraft and piezoelectric energy harvesting. This paper studies 1:2 internal resonance, nonlinear vibrations and chaotic snap-through phenomena of the bistable asymmetric composite laminated (BSCL) cantilever shell with the lower-frequency and higher-frequency primary resonances for the first time. The transverse foundation excitation subjects to the fixed end of the bistable cantilever shell. The perturbation analysis of two-degrees-of-freedom nonlinear ordinary differential equations is carried out by using the first-order approximate multiple scale method. The analytical results of the frequency-amplitude and force-amplitude response curves are obtained under the small foundation excitation. The obtained results reveal that the BSCL cantilever shell exhibits the double-jumping characteristics when 1:2 internal and primary resonances occur. There is a continuous energy exchange back and forth between two modes of the bistable laminated cantilever shell. As the foundation excitation increases, the BSCL cantilever shell exhibits saturation phenomenon. Numerical simulations are finished to further investigate the effects of the large excitation on the chaotic, quasi-periodic and snap-through vibrations for the BSCL cantilever shell. The vibration experiment is carried out to investigate the internal resonance and dynamic snap-though motions of the BSCL cantilever shell. Using the snap-though behaviors of the BSCL cantilever shell, we obtain the morphing structure of the aircraft wing. [ABSTRACT FROM AUTHOR]

This paper considers a wing system under unknown output disturbances, references, distributed disturbances and boundary disturbances. These signals have unknown frequencies, amplitudes and phases, and are then supposed to be from an exosystem with an unknown matrix. In this sense, we firstly find the wing system merely under the references and output disturbances, for which the PDE observer can be easily designed based on the measurable outputs. Then, an adaptive observer is designed for a detectable exosystem so that the references have known coefficients and approximately known states. Adaptive observer based controls are then proposed for the closed-loop system so that the convergence of tracking error and the boundedness of the states are guaranteed. Two simulation examples are compared to show the robustness of the designed controls. [ABSTRACT FROM AUTHOR]

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The wing-diesel hybrid ship, utilizes a wind propulsion system, which is significantly influenced by weather conditions. Therefore, a cooperative optimization method for course and speed is proposed based on an improved A* algorithm, considering weather changes and the ship characteristics, to achieve further improvement in the ship operational energy efficiency. Firstly, a meteorological and hydrological dataset is utilized to establish a dynamic maritime area model with complex weather conditions. Based on this model, the paper considers the actual navigation circumstances to define prohibited and navigable areas. Secondly, the improved A* algorithm incorporates the impact of weather on wing-sails. The improved A* algorithm considers the ship operating position and enhances the evaluation function by variables normalization of fuel consumption and voyage time. This cooperative optimization ensures the maximization of wind energy utilization, thereby achieving the goal of reducing fuel consumption while meeting the overall voyage time requirement. Experimental validation is conducted with the ship "New Aden" in the Indian Ocean region, and the results show that, compared to the original route, the optimized route reduces total fuel consumption by 5.48%, increases the navigation distance by up to 2.18% and increases the navigation time by 5.74%. • A cooperative optimization method of wing-diesel hybrid ship is proposed. • Improved A* algorithm is designed considering wing-sail and meteorological data. • Interpolation method is adopted to align meteorological data with ship data. • The algorithm evaluation function is calculated by variables normalization. • Optimized route reduces total fuel consumption by 5.48%. [ABSTRACT FROM AUTHOR]

Winglets have been employed in the aviation industry to reduce vortices generated at aircraft wings, decreasing drag, and hence increasing fuel economy. For rotating applications previous experimental and numerical studies addressed the application for wind turbines and suggested winglets facing backwards on the suction side of a blade could increase the power capture. This paper presents experimental work using a scale 3-bladed horizontal axis tidal turbine. An oil-based paint flow visualisation coupled to blade thrust and torque measurements helped to identify the mechanism behind the phenomenon affecting the performance of winglets facing the suction side of a turbine blade. The results show that on average a winglet facing downstream decreases the power coefficient 1–2% and increases the thrust coefficient up to 6% for tip speed ratios 5.0–7.0. On the other hand, a symmetrically mirrored winglet facing upstream increased the power coefficient by 1–2%, and the thrust coefficient by 3–4%. Winglets have the potential to provide a meaningful increase to power capture at minimal additional capital cost without increasing rotor diameters. Further work to optimize pressure‐side winglets should be conducted. [ABSTRACT FROM AUTHOR]

The advantages of Multidisciplinary wing development are only gradually being exploited in an industrial level, largely halted by the inevitable design space complexity arising from the interacting disciplines and objective constraints. An industrial tool has to provide design space exploration early in the design process and be reliable enough to guide subsequent fine-tuning optimization studies. In this paper, we display how our methodology can be used in an industrially relevant constrained aerostructural problem described by the common research model and formulated by the asymmetric subspace optimization architecture. It uses multi fidelity analyses in a surrogate based optimization framework, offering more detailed information earlier in the design cycle. The results indicate efficient space exploration, particularly due to the system level dimensionality reduction associated with such a load balancing architecture. [ABSTRACT FROM AUTHOR]

Aircraft like the Boeing 777-X use on-ground folding wingtips to meet the airport gate size restriction while increasing the aspect ratio during flight to reduce induced drag. A recent concept of aircraft design is to utilise in-flight floating wingtips as a means of load alleviation, which is known as semi-aeroelastic hinge (SAH). This device allows wingtips to be released during manoeuvre and severe gusts to alleviate wing loads, while locking the wingtips during cruise to maintain an optimum aerodynamic shape. This paper develops a flight mechanics model incorporating flexible wings to study the influence of the SAH device on multiple aspects of aircraft flight dynamics. The dynamic responses of the aircraft to gusts and control surface inputs are computed and compared for various hinge and wingtip configurations and release times. It was found that the gust load measured from the wing with free hinge configuration was approximately 40% lower compared to that of the fixed hinge case. It is also shown that when the SAH is released, it can significantly reduce an aircraft's roll damping and the frequency of the short-period mode, leading to higher roll and pitch rates. Furthermore, it shows that the transient responses following the wingtip release will exacerbate the responses induced by gusts, and greater load alleviation can be achieved by manipulating the hinge release time for each gust length. Finally, a step input of the elevator during the hinge release was found to be beneficial for enhancing the gust load alleviation. [ABSTRACT FROM AUTHOR]

The 4R-UAV project aims to develop aerodynamically efficient and environmentally friendly UAVs based on the 4R Circular Economy principle. In this study, the feasibility of the application of PFCDs (Passive Flow Control Devices) was investigated for the small-scale low-speed 4R-UAV wing. The application of PFCDs for small-scale UAV wings is relatively unexplored. Two PFCD types, i.e., MVGs (Micro Vortex Generators) and winglets, were considered for the investigations. In the stepwise investigations, the aerodynamic performance of the MVGs and the winglets was analyzed for the short-span 4R-UAV wing, which was developed from the aerodynamically optimized airfoil SG6043mod. MVGs enhanced the wings near stall properties (especially maximum lift coefficient) and contributed to the delayed wing stall of up to 2°. MVGs manifested the main aerodynamic advantage, which was achieved at the higher angles of attack. Winglets, on the other hand, were found to be extremely effective in cruise conditions with improved pre-stall characteristics. Extensive investigations on winglets were carried out by designing six winglet configurations for the 4R-UAV wing. Blended-type winglets performed well and enhanced pre-stall properties by decreasing the drag (up to 10%) of the wing. The main performance improvement was found in the early angles of attack. In the final step, the combined effect of the integrated PFCDs was analyzed. The final wing (integrated MVGs and winglets) also exhibited enhanced performance with nearly 6% increased lift-to-drag ratio in cruise conditions. The limited aerodynamic advantage achieved from the PFCDs in small-scale UAV applications can be useful in specific (civil or military) missions. Further verifications are planned in the future by means of experimental and flight testing. [ABSTRACT FROM AUTHOR]

The oscillatory pitch motion at the leading edge of a millimeter‐scale flexible sheet on the water surface can generate undulatory locomotion for swimming, similar to a honeybee vibrating its wings for propulsion. The influence of various parameters on such swimming strategy remains unexplored. This study uses magnetic milliswimmers to probe the propulsion mechanics and impact of different parameters. It is found that this undulatory propulsion is driven by capillary forces and added mass effects related to undulatory waves of the milliswimmers, along with radiation stress stemming from capillary waves at the interface. Modifying the parameters such as actuation frequency, pitch amplitude, bending stiffness, and hydrofoil length alters the body waveform, thus, affecting the propulsion speed and energy efficiency. Although undulatory motion is not a prerequisite for water surface propulsion, optimizing body stiffness to achieve a proper undulatory waveform is crucial for efficient swimming, balancing energy consumption, and speed. The study also reveals that the induced water flow is confined near the water surface, and the flow structures evolve with varying factors. These discoveries advance the understanding of undulatory water surface propulsion and have implications for the optimal design of small‐scale swimming soft robots in the future. [ABSTRACT FROM AUTHOR]

In this study, a control scheme is proposed based on Chaotic Particle Swarm Optimization (CPSO) to enhance the Linear Auto-Disturbance Rejection Controller (LADRC). The focus is on addressing the challenge of high-precision variations in angle-of-attack through dual-motor cooperative control within the lifting wing of a high-speed train. The scheme initiates with the design of a dual-loop structure for LADRC, integrating position and current control. The position loop is further refined. Subsequently, the CPSO algorithm is employed to optimize the parameters of the LADRC controller. Ultimately, the loop is closed by feeding back the position error in the cross-coupled structure to the current loop, thereby achieving high-precision control. The performance of the proposed structure is validated through both Matlab/Simulink simulations and an experimental platform. The experimental results demonstrate that CPSO-LADRC, in comparison to traditional LADRC and Proportion-Integration-Differentiation (PID) control, exhibits an increase in the maximum response time by 3.76 s and 3.3 s, respectively, a reduction in overshoot by 1.12% and 0.8%, as well as a decrease in the maximum synchronization error by 0.45 cm and 1 cm, respectively. These findings validate the effectiveness of the proposed synchronous loop controller method in simplifying computational complexity, enhancing system responsiveness, robustness, and synchronization performance. Additionally, our approach facilitates precise angle-of-attack transformation for the lifting wings of high-speed trains effectively. [ABSTRACT FROM AUTHOR]

The evolution of aircraft wing development has seen significant progress since the early days of aviation, with static testing emerging as a crucial aspect for ensuring safety and reliability. This study focused specifically on the engineering phase of static testing for the Clean Sky 2 T-WING project, which is dedicated to testing the innovative composite wing of the Next-Generation Civil Tiltrotor Technology Demonstrator. During the design phase, critical load cases were identified through shear force/bending moment (SFBM) and failure mode analyses. To qualify the wing, an engineering team designed a dedicated test rig equipped with hydraulic jacks to mirror the SFBM diagrams. Adhering to specifications and geometric constraints due to several factors, the jacks aimed to minimize the errors (within 5%) in replicating the diagrams. An effective algorithm, spanning five phases, was employed to pinpoint the optimal configuration. This involved analyzing significant components, conducting least square linear optimizations, selecting solutions that met the directional constraints, analyzing the Pareto front solutions, and evaluating the external jack forces. The outcome was a test rig setup with a viable set of hydraulic jack forces, achieving precise SFBM replication on the wing with minimal jacks and overall applied forces. [ABSTRACT FROM AUTHOR]

This study addresses the crucial role of post-buckling behavior analysis in the structural design of composite aeronautical structures. Traditional engineering practices tend to result in oversized composite components, increasing structural weight. EASA AMC 20-29's Building Block Approach suggests phased testing, but its time and cost challenges necessitate a shift to high-fidelity post-buckling analyses, exemplified by MSC NASTRAN SOL 400. This approach, showcased in the analysis of the Next Generation Civil Tilt Rotor Technology Demonstrator's wing (NGTCTR-TD), effectively de-risks static tests, contributing to a more efficient certification process. The study demonstrates how advanced simulations provide detailed insights into local buckling phenomena, allowing precise stress distribution analysis. These analyses eliminate the risk of structural failure, paving the way for safer, more efficient, and cost-effective airframe structures. Future developments aim to validate numerical analyses with experimental data, further emphasizing the reliability and benefits of high-fidelity simulations. [ABSTRACT FROM AUTHOR]

Lightweight structures with a high stiffness-to-weight ratio always play a significant role in weight reduction in the aerospace sector. The exploration of non-conventional structures for aerospace applications has been a point of interest over the past few decades. The adaptation of lattice structure and additive manufacturing in the design can lead to improvement in mechanical properties and significant weight reduction. The practicality of the non-conventional wing structure with lattices infilled as a replacement for the conventional spar–ribs wing is determined through finite element analysis. The optimal lattice-infilled wing structures are obtained via an automated iterative method using the commercial implicit modeling tool nTop and an ANSYS workbench. Among five different types of optimized lattice-infilled structures, the Kelvin lattice structure is considered the best choice for current applications, with comparatively minimal wing-tip deflection, weight, and stress. Furthermore, the stress distribution dependency on the lattice-unit cell type and arrangement is also established. Conclusively, the lattice-infilled structures have shown an alternative innovative design approach for lightweight wing structures. [ABSTRACT FROM AUTHOR]

System-of-systems (SoS) warfare has become the main form of modern warfare, where various equipment interact and interconnect to achieve operational goals. The complexity of equipment SoS poses a challenge for evaluating equipment under such warfare environments, as it requires considering multiple elements such as tasks and capabilities to ensure reliable evaluations. This paper proposes a novel equipment evaluation approach for SoS warfare environments based on the intuitionistic fuzzy weighted influence non-linear gauge system (IF-WINGS). The approach employs intuitionistic fuzzy sets (IFS) to represent uncertain information related to tasks, capabilities, and equipment. By extending the WINGS method with IFS, the proposed approach uncovers the interdependencies among the elements within the equipment SoS using the causal relation graph, considering both the strength and influence intensity of these elements. Additionally, the proposed approach evaluates and ranks different alternatives using relative closeness, which takes into account the distance of each alternative from the best and worst solutions, and this enables a more reliable and effective evaluation of alternatives. A novel equipment evaluation approach that considers the interrelationships among various elements within the equipment SoS is introduced based on IF-WINGS. To demonstrate the effectiveness of the proposed method, a case study is presented, and the results are compared to other methods, with Spearman's rank correlation coefficients of the comparative methods obtained as (0. 96 , 0. 96 , 1. 00 , 1. 00) , respectively. The results show that the proposed method could provide reliable and robust results for equipment evaluation in SoS warfare environments. By introducing the IF-WINGS method into equipment evaluation under SoS environment, this study provides a novel and effective way that considers the complex relationships among different elements in SoS warfare, enabling reliable and reasonable evaluation. In conclusion, the IF-WINGS method proves to be a valuable tool for assessing equipment performance in complex and interconnected warfare scenarios. • Proposed a novel approach for equipment evaluation in SoS warfare based on IF-WINGS. • IFS is used to represent uncertain judgments on the equipment. • Causal relation graph is used to reveal interdependencies among elements of the equipment SoS. • Relative closeness is introduced to enable robust alternative ranking. • A real case of equipment evaluation under SoS warfare is presented. [ABSTRACT FROM AUTHOR]

Variable swept wing is one important type of morphing aircrafts for adaptation between high and low speed flight. In this paper, a deformable mechanism is presented for hypersonic variable-swept-wing aircraft by means of redundant actuation. A design and optimization method is proposed to devise this mechanism through two steps. In the first step, a multi-objective optimization method is presented to optimize the link lengths of a peripheral slider-rocker mechanism driven by a slider actuator. Three factors are considered: transmission angle, overall linkage size and mechanical efficiency. The proposed optimization method is implemented by combining NSGA-Ⅱ algorithm with the MATLAB optimization tool. In the second step, extra slider-rocker mechanisms are added inside the peripheral mechanism to form a multiple active chain mechanism to redundantly drive the same leading edge for force sharing. A force analysis method is proposed to determine the distributed actuator forces using a method for structurally indeterminate systems. The proposed two-step method is implemented on case studies of two and three redundant chains. The accuracy of the theoretical results are verified to be higher than 90% by commercial software ADAMS simulation during the deformation stabilization. The agreement between the two results manifests that the proposed method is effective, and that redundant chains can indeed distribute the actuation forces for compact space design. A prototype is fabricated to verify the feasibility of the design. [ABSTRACT FROM AUTHOR]

This paper represents a single component multi-rate Real-Time Hybrid Simulation (mrRTHS) strategy for structural assessment of a cantilever Glass Fiber Reinforced Polymer (GFRP) beam loaded at the tip by a sinusoidal point load. This emulated structure is implemented as a simplified wind turbine blade in terms of geometry, scale and load – here with special attention paid to the root and max-chord section. Thus, the experimental substructure comprises the clamped end of the GFRP beam while the free end makes up the numerical substructure. The partitioning between the numerical and experimental substructure – referred to here as the shared boundary – includes a discrete point with 3 degrees-of-freedom (dof). The numerical substructure generates a displacement signal through a Taylor basis with a coarse time step to optimize computational resources. Using the previous displacement data points, a finer control signal is generated to ensure accurate actuator control in the transfer system. A DIC and inertia compensator is implemented to account for the compliance and dynamics imposed by the load train in the transfer system. The structural response is investigated by mrRTHS for an execution frequency in the range: 0.074 Hz – 2.96 Hz for the sinusoidal point load. The system performance is evaluated against an experimental test setup of the emulated structure – referred to here as the experimental reference. With a root-mean-square (RMS) error in the order of 8–20% between the mrRTHS and reference, the system proved successful in terms of stability and overall correlation at the shared boundary, which is considered an important milestone towards single component mrRTHS on a structure like e.g. a wind turbine blade, aircraft wing or similar cantilever-shaped large load carrying structure. • Demonstration of a single component hybrid simulation strategy capable of handling a complex partitioning. • mrRTHS strategy enables accurate actuator control by operating the numerical substructure at two different rates. • Successful single component multi-rate real-time hybrid simulation demonstrated on a cantilever beam loaded at the tip. [ABSTRACT FROM AUTHOR]

Over the last few decades, multirotor UAVs have become significantly popular because of their various applications. However, multirotors suffer from poor endurance performance as compared to other aircraft configurations with lifting surfaces. This limitation can be addressed by improving the technology of components or by developing design optimization approaches at the vehicle level. This paper presents a co-design approach for the multirotor structure and propulsive system to improve the vehicle's energetic efficiency while respecting dynamic performance requirements. For this purpose, the approach uses a bi-level formulation to optimize the design and control concurrently. The methodology offers the possibility to activate or not a passive fault tolerant strategy in the controller synthesis to be tolerant to single rotor failure. In contrast to conventional design approaches that sequentially design each part, the co-design approach leads to a better optimal solution by considering the interactions and couplings between design and control. With the proposed co-design approach, the results show the soundness of the proposed design methodology and a significant reduction in the consumed energy compared to a reference non-optimal design while maintaining the same requirements in terms of dynamic performance. [ABSTRACT FROM AUTHOR]

The aeroelastic response of lightweight low-speed aircrafts with slender wings under extreme flow turbulence intensity is not well understood. Experiments on a commercial unmanned aerial vehicle (UAV) with a 3 m wingspan and aspect ratio of 13.6 were performed in a large open-return wind tunnel with extreme flow turbulence intensity of ≈10%. The wing bending displacement and the flow beneath the wing were measured by using laser-displacement sensors and tomographic particle image velocimetry (PIV) techniques, respectively. The unsteady lift produced by the wing was also measured by using a high-capacity load cell at an angle of attack of two degrees for three freestream velocities of 13.4 m/s, 17.9 m/s, and 26.8 m/s, representing the UAV's stall speed, a speed approximately equal to the cruise speed, and a speed considerably higher than the cruise speed, respectively. It was found that a high flow turbulence intensity with large integral length scales relative to the wing chord plays a dominant role in the large unsteady lift and wing displacements measured. The power spectral density (PSD) of the wing structural vibration shows that flow shedding from the wing and the integral length scales have a significant impact on the overall power inherent in the bending vibration of the wing. Computations of the vorticity isosurfaces in the flow measurement volume surrounding the aileron reveal a striking observation: an aileron deflection of 10° becomes less effective in producing additional spanwise vorticity, which is proportional to circulation and lift at 26.8 m/s since the freestream already has elevated levels of vorticity. A paradigm shift in design is suggested for light aircraft structures with slender wings operating in highly turbulent flow, which is to employ multiple control surfaces in order to respond to this flow and mitigate large bending or torsion displacements and the probability of structural failure. [ABSTRACT FROM AUTHOR]

Lightning is one of the natural hazards that any aircraft may encounter while navigating. If adequate precautions are not taken against lightning, structural damage, operational disruptions, and loss of life and property can occur. Thus, studying the mechanism of damage caused by lightning strikes in an aircraft's structural material is necessary to optimize the structure, minimize the damage, and reduce the cost caused by lightning. In the present article, the lightning-induced damage behavior of an aircraft structural material was investigated from an analytical perspective. For this purpose, two analytical-based models were developed: an improved electromagnetic pressure impact model (IEPIM) and the damage model in an aircraft wing. For the IEPIM, the findings of the article showed that the proposed pressure model is in good agreement with the experimental studies, borrowed from the open literature, for 100 and 200 kA lightning current. For the damage model, the findings of the article indicated that (i) even though lightning strikes to the regions with the same characteristics on an aircraft wing in terms of the lightning strike zone, the amount of deflection in the wing increases as the impact point approaches the wing tip and decreases as it approaches the wing root, (ii) without changing the lightning strike point (x 0), when the damping coefficient (ξ) is increased in the range of 0 , 2 ξ , the amount of deflection decreases as the amount of damping coefficient increases, and (iii) when lightning with a current of 100 kA hits to the wing root of an aircraft, the pressure impact of the lightning causes more torsion deflection than bending deflection at the wing root; however, when it hits to the mid-wing or wing tip of an aircraft, the pressure impact of the lightning causes more bending deflection than torsion deflection at the mid-wing or wing tip. [ABSTRACT FROM AUTHOR]

Distributed electric propulsion (DEP) with four propellers distributed along the rear edge of the wing (pusher DEP configuration) promote aerodynamic interactions to a higher level. To study the aerodynamic performance of DEP with the rear wing through simulations and experiments, the multi-reference frame (MRF) with sliding grid is combined with wind tunnel tests. The obtained results demonstrate that the lift and drag of DEP increase with the angle of attack (AoA) and are related to the relative position of the propellers and wing. The propeller has no significant effect on the lift of the wing, and the lift and the AoA remain linear when the AoA is less than 16°. By contrast, the lift coefficient is much higher than the baseline (isolated wing), and the lift is greatly improved with the increasing drag when the AoA is greater than 16°. This is because the flow around the wing of the pusher configuration remains attached due to the suction of the inflow of the propeller on the trailing edge vortex. In addition, the acceleration effect on the free flow improves the kinetic energy of the airflow, which effectively delays the separation of the airflow in the slipstream region. [ABSTRACT FROM AUTHOR]

A conceptual framework is presented to determine the improvement in the aerodynamic performance of a canard aircraft fitted with distributed propellers along its main wing. A preliminary study is described with four airframe–propeller configurations predominantly studied in academic and commercial designs. The leading edge–based tractors and trailing edge–based pushers are identified as configurations of interest for the main study. Subsequently, a Navier–Stokes solver is used to simulate the flow using two numerical approaches–a modified steady-state actuator disk and an unsteady rotating propeller profile. Moving meshes with rotating sub-domains are used with a hybrid RANS-LES-based turbulence model while the actuator disks are modified to include viscous swirl effects. The preliminary study shows a local minimum in the change in C L and C D at 10 ∘ for the pusher and tractor configurations. The main study then demonstrates the outperformance of the pushers over tractors quantified using C L and C L / C D . There is a clear preference for the pushers as they increase the lifting capacity of the aircraft without disproportionately increasing the drag due to the flow smoothening by the suction of the pusher propellers over the main wing. The pushers also delay the separation of the boundary layer whereas the tractors are unable to prevent the formation of the separation bubble despite injecting momentum through their slipstreams into the flow. The results from the two numerical approaches are then compared for accuracy in designing DEP configurations for an airframe. [ABSTRACT FROM AUTHOR]

The design and development of a wing for a completely brand-new aircraft represents, in aeronautics, one of the highest challenges from an engineering point of view. The present work describes a novel methodology devoted to execute numeric simulation in a non-linear post-buckling regime to verify the composite wing compliance under the design load conditions. The procedure was developed as part of a wing design and research activity and was motivated by the need to have more realistic results, without standard conservatisms like the no-buckling up to ultimate load, to be of use for achieving further weight savings. To carry this out, it was obviously necessary to ensure that the structural integrity was also guaranteed in the post-buckling regime, above the limit load, and therefore in a highly non-linear regime. The present work illustrates a numerical approach based on non-linear finite element analysis which uses the inertia relief option in order to have a more realistic representation of the structural response of the wing in its real context. All that represents a novelty since, at present, the commercial FE codes allow us to use the inertia relief option exclusively for linear analysis. Obviously, the approach can be applied to any other structural component with similar needs. The obtained results show that the differences between linear and non-linear regime are not negligible and, above all, that it is possible to design a wing (or other structural components) considering, at the same time, the large deformation due to the post-buckling regime, the material non-linearities due to the failures and any other non-linearities in order to achieve the challenging weight requirement of the new aircraft generation. [ABSTRACT FROM AUTHOR]

Marine monitoring equipment such as Argo profiling buoys and underwater gliders are important devices for oceanographic research and marine resource exploration. In this study, a novel mobile buoy capable of vertical profiling motion like Argo profiling buoys and sawtooth gliding motion like underwater gliders is proposed. The proposed mobile buoy can switch between the two motion modes with controllable wings. To verify the feasibility of the proposed mobile buoy, a fluid–multibody coupling model considering multibody dynamics and hydrodynamics was developed to investigate the dynamic response. A scaled-down buoy prototype was fabricated and the feasibility of the two motion modes was experimentally investigated in a laboratory tank. The experimental results agree well with the results of numerical simulation. This work can be helpful for the design and analysis of this kind of mobile buoy. [ABSTRACT FROM AUTHOR]