Search Results (113)

Fast and reliable aerodynamic predictions are crucial in the early phases of aircraft design, where a quick assessment of various configurations is required. In this context, the Vortex Lattice Method (VLM) is widely adopted due to its computational efficiency; however, its predictive accuracy is highly sensitive to panel discretization strategies, which are often determined heuristically. This study proposes a bio-inspired optimization framework for VLM panel discretization and evaluates it through a systematic case study on a representative wing geometry. A grid-convergence analysis was initially carried out to ensure solution independence across various spanwise-to-chordwise panel ratios. Subsequently, a novel Hybrid Response Surface Methodology (HRSM), integrating Box–Behnken and Central Composite experimental designs, was employed to enable a more comprehensive exploration of the factor space while quantifying the effects of clustering parameters at the leading-edge, trailing-edge, root, and tip regions of the wing. The HRSM dataset was further utilized to train Ensemble Machine-Learning surrogate models, which were coupled with bio-inspired Crayfish and Aquila optimization algorithms, alongside a classical Genetic Algorithm (GA) as a performance benchmark, to identify the optimal discretization strategy and to enable a comparative assessment of their convergence behavior and robustness against the numerical noise of the ensemble-based landscape. Compared to base (i.e., uniform) panel distribution, the optimally clustered discretization enhanced overall aerodynamic prediction accuracy by approximately 33%, particularly at low angles of attack, while maintaining robust performance at higher angles. Both algorithms converged to similar minima; however, the Aquila algorithm achieved higher solution consistency, whereas the Crayfish algorithm exhibited greater dispersion despite faster convergence, revealing a multimodal optimization landscape. The variance decomposition revealed that trailing-edge clustering dominated aerodynamic accuracy at low angles of attack, contributing up to 90% of the total variance, whereas tip clustering became increasingly influential at higher angles, exceeding 30%, highlighting the need for adaptive discretization strategies to ensure reliable VLM-based aerodynamic analyses. Full article

Airframe noise generated at wing trailing edges and high-lift devices, such as flaps, remains a major challenge during landing, with significant contributions in the low-frequency band of 500–1500 Hz. While solid surfaces reflect this acoustic energy, metallic porous materials can effectively absorb it through viscous and thermal dissipation within their internal pore structure. To address this, the present study examines the acoustic absorption characteristics of open-cell AlSi porous cylinders featuring controlled pore diameters between 0.3 mm and 2.25 mm. Measurements were conducted in an acoustic impedance tube according to the ISO 10534-2:2023 standard, using six cylindrical samples (28 mm diameter, 70 mm length). Two sets of measurements were performed for each sample (front and rear faces), and the average values were used. The findings indicate that the normal-incidence sound absorption coefficient α rises as pore size increases, reaching 0.93–0.97 at low frequencies of 500–700 Hz for the samples with the largest pores (1.8–2.25 mm). These results indicate that open-cell AlSi alloys offer strong low-frequencies sound absorption, positioning them as promising options for aeroacoustic noise mitigation, including applications such as porous trailing edge and hybrid flap designs. Full article

Recently, continuous improvements in aircraft manoeuvrability and fuel consumption reduction have led researchers to investigate additional wing configurations based on morphing concepts. Morphing is also a potential solution for noise level reduction and may therefore represent an additional benefit. The advantages of morph-type schemes over traditional control surfaces during specific manoeuvres become a key parameter in the preliminary design stage. In this work, three types of airfoil morphing applied to a typical basic wing are considered and analysed: leading-edge morphing, trailing-edge morphing, and rib twist. The aerodynamic performance of each configuration is evaluated through a numerical procedure combining a panel method and a vortex lattice method. Drag reduction in morphed versus conventional wings under identical flight conditions is quantified, allowing the identification of the most efficient configuration. The analyses consider both roll manoeuvres and high-lift flight phases by evaluating changes in design parameters—such as chord-wise hinge positions, span-wise morph distribution, and morphing angles—which are compared and discussed. For the rolling manoeuvre, increasing the span-wise morphing region improves drag reduction, but not by more than 5%. When shifting the hinge position from 60% to 80% of the chord, similar drag reduction levels can be achieved, although the required morph angle differs under the same conditions. The effect of different drag components is also assessed, showing that the induced drag component is predominant for low aspect ratio wings, whereas parasite drag becomes significant at higher aspect ratios. Optimal geometrical configurations are presented and discussed for both manoeuvres. For the rolling, hinge positions yielding typical rolling moment coefficients (i.e., −0.05, −0.06, and −0.08) lie between 65% and 75% of the chord, with span-wise morphing ranges 40% < y_rib < 60% producing drag reduction up to 40% compared with a conventional wing. For the high-lift conditions, configurations between 65% < x_hinge < 80% and 50% < y_rib < 90% allow a drag reduction which can go up to 60%. Another beneficial effect is also observed for the yawing moment coefficient C_n with a reduction of more than 20% for larger aileron surfaces. Full article

Bionic airfoils are an effective method to improve aerodynamic performance and reduce the noise of wind turbine blades. To explore the impact of the lower surface of bird wing airfoils on the aerodynamic performance and noise of blades, this study combines the upper surface of the NACA0018 airfoil with the lower surfaces of the teal, long-eared owl, and sparrowhawk (CBA-T, CBA-O, CBA-S) to create three new composite bionic airfoils (CBAs). The aerodynamic performance of these airfoils is evaluated, and the CBA-O airfoil is identified as having the best aerodynamic characteristics. A comparison of the noise and vortex structures of the CBA-O, owl wing airfoil, and NACA0018 is conducted, and the mechanisms behind the CBA-O airfoil performance improvement and noise reduction are explored. The results indicate that the CBAs enhance the aerodynamic performance of the airfoils. Before stall, the aerodynamic performance of the CBA-O improves the lift-to-drag ratio by 12.7% and 119.7% compared to the owl and NACA0018 airfoils, with its average SPL significantly lower than that of the NACA0018. The CBA-O has smaller vortex sizes at the trailing-edge, and the wake vortex develops more stably, effectively reducing both surface radiation noise and wake noise. Full article

Transonic shock buffet is a complex flow phenomenon characterized by self-sustained shock oscillations, which severely limits the flight envelope of modern civil aircraft. While Shock Control Bumps (SCBs) have been widely studied for drag reduction, their potential for delaying the buffet boundary on swept wings has yet to be fully explored. This study employs numerical analysis to investigate the efficacy of three-dimensional (3D) contour SCBs in delaying the buffet boundary of the NASA Common Research Model (CRM) wing. The buffet boundary is identified using both the lift-curve slope change and trailing-edge pressure divergence criteria. The results reveal that 3D SCBs generate streamwise vortices that energize the boundary layer, thereby not only weakening local shock strength but, more critically, suppressing the spanwise expansion of shock-induced separation. Collectively, the reduction in shock strength and the containment of spanwise separation delay the buffet boundary, thereby improving the aerodynamic efficiency of the wing. Two configurations, designed at different lift conditions (SCB-L at $C_L=0.460$ and SCB-H at $C_L=0.507$), demonstrate a trade-off between buffet delay and off-design drag reduction. The SCB-H configuration achieves a buffet boundary lift coefficient improvement of 6.3% but exhibits limited drag reduction at lower angles of attack, whereas the SCB-L offers a balanced improvement of 4.0%, with a broader effective drag-reduction range. These results demonstrate that effective suppression of spanwise flow is key to delaying swept-wing buffet and establish a solid reference framework for the buffet-oriented design of SCBs. Full article

In response to the significant threat posed by low-frequency P-band anti-stealth radar to aircraft stealth capabilities, this paper examines the inverse design of electromagnetic parameters for a single-layer, thin P-band radar absorbing material. An efficient computational model is constructed by integrating impedance boundary conditions with the characteristic basis function method. The NSGA-II genetic algorithm is employed to accomplish multi-objective co-optimization of electromagnetic parameters and material thickness. Results demonstrate that the optimized single-layer RAM, with a relative permittivity of μ_r = 3.3078 + j3.9018 and permeability of ε_r = 2.3522 + j6.9519, exhibits outstanding P-band absorption characteristics within a thickness constraint of only 1 mm. Applying this RAM to aircraft wing components’ leading/trailing edges, intake duct cavities, and lip areas effectively suppresses edge diffraction and cavity scattering. The target achieves a maximum forward average RCS reduction of −13.97 dB and a maximum rearward average RCS reduction of −5.03 dB, maintaining stable performance within a pitch angle range of 0° ± 5°. Full article

Inspired by the movements of sea turtle forelimbs, this study presents a bio-inspired underwater flapping wing with three degrees of freedom. This flapping wing mechanism can more accurately simulate the rotational motion of a sea turtle’s forelimbs to generate greater propulsive force. The highlight is the gear transmission mechanism arranged along the wingspan, enabling a preset increasing twist angle along the wingspan. Computational fluid dynamics simulations are conducted to evaluate the hydrodynamic performance of the proposed flapping wing system. The effects of different spanwise twist angles along the wingspan on thrust generation are quantitatively analyzed, as well as the influence of key kinematic parameters, including the longitudinal flapping angle, spanwise increasing twist angle, and elevation angle. The results indicate that, compared with a uniform twist angle, the spanwise increasing twist significantly increases the peak thrust during specific phases of the flapping cycle. It is further revealed by flow field analyses that the formation of vortices near the trailing edge enhances the propulsive force in the streamwise direction. To further validate the proposed concept, a prototype of the mechanism is fabricated and experimentally tested under low-frequency actuation, confirming the feasibility of the mechanical design. Overall, these results demonstrate the potential of the proposed approach for bio-inspired underwater propulsion and provide useful guidance for future flapping wing mechanisms and kinematic design. Full article

This study employed numerical simulations to investigate the aerodynamic characteristics of a flapping wing by solving the governing incompressible Navier–Stokes equations. Using computational fluid dynamics (CFD), the effect of frequency acceleration on the aerodynamic performance of a two-degrees-of-freedom (DoF) flapping wing in hovering was examined. The results indicate that the pitching frequency acceleration significantly influences the aerodynamic force: positive acceleration enhances lift by up to 2.0 times while maintaining propulsion compared to the case under negative acceleration. This mechanism is attributed to the delayed shedding of the leading-edge vortex (LEV) and the shedding of the trailing-edge vortex (TEV). Moreover, aerodynamic forces are also affected by plunge acceleration, with both negative and positive acceleration contributing to performance improvement. An increase in the acceleration coefficient leads to a notable enhancement in the aerodynamic force; however, the improvement becomes marginal when the coefficient n exceeds 0.4. The underlying flow evolution is illustrated and analyzed through pressure and vorticity contours. These findings on the acceleration effect will be applied to optimize the kinematics and design of flapping wing drones. Full article

During the hammer riveting of aircraft composite wing trailing edges, issues such as unclear damage mechanisms resulting from the continuous impact loading of composite materials, difficulty ensuring connection strength, and issues with damage control remain unresolved. This study investigates the dynamic impact load transfer mechanism during hammer riveting, establishes a model which maps the correlation between impact loads and rivet plastic flow, and develops a composite material VUMAT subroutine (a user-defined material subroutine in Abaqus/Explicit) based on the 3D Hashin failure criterion. A progressive damage simulation model for composite materials subjected to multiple hammer riveting operations is constructed. Based on mechanical analysis, a double-sided countersunk rivet with a support structure is proposed to suppress damage during composite hammer riveting. Simulation and experimental analysis demonstrate that, compared to conventional rivets, the new rivet effectively reduces contact stress (by up to 32.29%). Damage zones are concentrated at the straight hole and at the junction between the straight and countersunk holes. Furthermore, damage modes are simplified to matrix compression and tensile stress, with their respective proportions decreasing by 16.7% and 25.9%. Full article

This project’s focus is to create a morphing wing with variable geometry that will improve aerodynamic performance. The NACA 0018 airfoil, known for its stable aerodynamic characteristics and symmetrical shape, is chosen as a base airfoil for modification in this approach. To investigate the effects of flexible trailing edge deformation under aerodynamic loading, various new morphing airfoil designs have been designed and analyzed. Both the performance results of a conventional hinged wing design and morphing airfoil designs were compared. Identifying the most effective airfoil design that could produce higher lift-to-drag ratios, less turbulence, and better overall aerodynamic behavior was the main goal. Because of its elasticity and flexibility, natural rubber latex (Hevea brasiliensis) was utilized as the primary skin material. This allows for a seamless, hinge-free morphing wing. To evaluate aerodynamic efficiency, structural integrity, and material behavior under various situations, computational fluid dynamics simulations were carried out. The most promising airfoil design was determined based on performance. By reducing drag, increasing lift, and reducing mechanical complexity, this new approach offers a sustainable and effective substitute for traditional wing designs, advancing the development of adaptive aeronautical structures. Full article

In this research, two inflatable-winged Unmanned Aerial Vehicles (UAVs) in distinct configurations, a single-fuselage layout with external trailing-edge control surfaces and a twin-fuselage layout with fully movable control surfaces were designed, developed, and flight tested to investigate the flight characteristics of inflatable-winged aircraft. Initially, inflatable wings were designed and fabricated from various materials, followed by rigorous ground testing, including structural characteristics tests, pressure retention and resistance tests, and low-speed wind-tunnel evaluations. Following this, two methods for controlling the inflatable wings were proposed, and their roll control effectiveness was thoroughly investigated. Subsequently, two inflatable-winged UAV prototypes, each employing a different configuration and manipulation method, were designed, assembled, and subjected to basic low-altitude flight tests to assess the feasibility of their aerodynamic layouts and control characteristics. The results demonstrated that a segmented wing design with a multi-boom configuration is particularly well-suited for inflatable wings. Additionally, both proposed control methods were tested and shown to be effective in flight. The findings provide valuable insights into the properties of inflatable wings and offer substantial guidance for the development of inflatable-winged aircraft. Full article

This work presents a low-fidelity optimization method for a compliant morphing wing trailing-edge structure, developed to achieve multiple optimized aerodynamic shapes under combined aerodynamic and control loads using a single actuation pathway. Typically, multiple shape configurations are avoided due to conflicting structural requirements that increase optimization complexity. To address this, a parameterization method based on practical considerations of compliant trailing-edge structures is introduced. A particle swarm optimization algorithm is employed, with multi-objective criteria handled through a penalty-based approach. The algorithm is demonstrated by optimizing the trailing edge for one and two aerodynamic configurations with high accuracy, achieving typical shape deviations of 0.04% and 0.08% relative to the chord for two shapes, and as low as 0.023% for a single shape. Several compliant structures are generated, manufactured, and tested for shape accuracy, including in a wind tunnel to evaluate aerodynamic performance. Experimental investigations confirm the feasibility of achieving two aerodynamic shape configurations with a single structure and show that the proposed methodology can improve the lift-to-drag ratio of a wing section with a deflected compliant trailing edge by more than 12.4% compared to conventional flaps at the same deflection. Full article

This encyclopedia entry provides an updated appreciation of the evolution of morphing aircraft wings, organized as follows: first, lift concepts are briefly examined; second, patents related to lift enhancement are discussed, showcasing existing technology and its evolution; finally, several technologies for morphing wings and the role of UAVs as testbeds for many innovative concepts are highlighted. The background of morphing wings is presented through a recap of lift concepts and the presentation of representative patents that describe the evolution of leading-edge and trailing-edge devices, such as flaps, slats, spoilers, and control surfaces. Although these topics are not usually detailed in reviews of morphing wings, they are deemed relevant for this encyclopedia entry. Full article

Aircraft performance metrics such as range and endurance are highly dependent on induced and vortex drag. There is a close relationship between wake structure and aerodynamic performance. In the present paper, the velocity field behind the model of a wing with winglet is studied. The methodology and equipment for study in a low-speed wind tunnel ULAK–1 are presented. The pressure field was obtained using a five-hole pressure probe, which was positioned in a cross plane at 300 mm behind the wing trailing edge. The acquired experimental data are used to calculate the cross flow velocity and vorticity fields at an angle of attack of 6 degrees—around the maximum lift-to-drag ratio. The results are compared to the data of a model with planar wing. During the subsequent processing, coefficients of lift and induced drag can be obtained. Full article

As a commonly used configuration for advanced unmanned aerial vehicles (UAVs), the flying-wing configuration suffers from pitching moment trimming issues due to the lack of horizontal tail. The UAV either needs to unload lift at the trailing edge or needs to increase the wingtip twist angle at the cost of losing the lift-to-drag ratio. The commonly used methods for solving pitching moment trimming issues are compared and analyzed in this paper, and it is found that the method of trailing-edge twist has advantages under cruising lift coefficient. Furthermore, a trailing-edge twist deformation parameterized model that can deform multiple critical sections is designed with relevant grids. The multi-objective genetic algorithm is used to optimize the parameterized model and obtain the optimized results. Through comparative analysis, it is found that the optimized trailing-edge twist model has an advantage in distributing the pitching moment. By optimizing the distribution of aerodynamic forces and moments, cruise trim is achieved with only a 1.43% cost to the cruise lift-to-drag ratio compared to the initial model. Full article