Bio-inspired Wing Research Articles

Effects of Bio-Inspired Wing Dihedral Variations on Dynamic Soaring Performance of Unmanned Aerial Vehicles

On the basis of a self-developed albatross imitation unmanned aerial vehicle (UAV), three different dihedral angle configurations for the wing’s mid and outer sections are explored: fixed at −50°, fixed at −5°, and varying arbitrarily between −50° and −5°. By solving the optimal loitering dynamic soaring trajectory optimization problem for each configuration, the effect of dihedral angle variation on the dynamic soaring performance of the bio-inspired wings is investigated. The results indicate that under all three configurations, the UAV achieves energy-neutral flight in specific wind field environments. Compared to the fixed dihedral angle of −5°, the UAV demonstrated superior dynamic soaring performance when the dihedral angle was fixed at −50°. When the dihedral angle varied dynamically, the UAV outperformed both fixed configurations across all relevant parameters. Specifically, compared to the fixed dihedral angle of −5°, the total energy increased by 25.43%, and the minimum required wind gradient decreased by 15.56%. Similarly, compared to the fixed dihedral angle of −50°, the total energy increased by 2.52%, and the minimum required wind gradient decreased by 2.07%. These findings suggest that the use of variable dihedral angle technology in bio-inspired UAV wings can significantly enhance dynamic soaring performance and provide theoretical support for the design of morphing wings with superior dynamic soaring capabilities.

Biomimetic Wings for Micro Air Vehicles.

In this work, micro air vehicles (MAVs) equipped with bio-inspired wings are investigated experimentally in wind tunnel. The starting point is that insects such as dragonflies, butterflies and locusts have wings with rigid tubular elements (corrugation) connected by flexible parts (profiling). So far, it is important to understand the specific aerodynamic effects of corrugation and profiling as applied to conventional wings for the optimization of low-Reynolds-number aerodynamics. The present study, in comparison to previous investigations on the topic, considers whole MAVs rather than isolated wings. A planform with a low aperture-to-chord ratio is employed in order to investigate the interaction between large tip vortices and the flow over the wing surface at large angles of incidence. Comparisons are made by measuring global aerodynamic loads using force balance, specifically drag and lift, and detailed local velocity fields over wing surfaces, by means of particle image velocimetry (PIV). This type of combined global-local investigation allows describing and relating overall MAV performance to detailed high-resolution flow fields. The results indicate that the combination of wing corrugation and profiling gives effective enhancements in performance, around 50%, in comparison to the classical flat-plate configuration. These results are particularly relevant in the framework of low-aspect-ratio MAVs, undergoing beneficial interactions between tip vortices and large-scale separation.

Bio-Inspired Wing With Bistable Morphing Airfoils for Aquatic-Aerial Robots

Bio-Inspired Wing With Bistable Morphing Airfoils for Aquatic-Aerial Robots

Unsteady load alleviation on highly flexible bio-inspired wings in longitudinally oscillating freestreams

This study delves into the aerodynamic behaviour of a highly flexible NACA 0012 aerofoil, drawing inspiration from avian feathers to handle a gust. We first examined unsteady flow on a rigid wing both experimentally and numerically and then explored the implications of introducing wing flexibility purely numerically. Our findings underscore the potential of composite materials in alleviating the oscillating aerodynamic forces on a wing under a streamwise gust. This behaviour is attributed to its capacity to destabilize the laminar separation bubble, fostering a more stable turbulent boundary layer. While direct avian evidence remains limited, it is postulated that in nature, such mechanisms could mitigate undesired wing flapping, optimizing energy consumption in perturbed environments.

Bioinspired Genetic-Algorithm Optimized Ground-Effect Wing Design: Flight Performance Benefits and Aircraft Stability Effects

This paper presents a bioinspired, genetic-algorithm evolutionary process for Ground-Effect vehicle wing design. The study made use of a rapid aerodynamic model generation and results evaluation computational fluid dynamics vortex lattice method software, supervised by a genetic algorithm optimization Python script. The design space for the aircraft wing parametric features drew inspiration from seabirds, under the assumption of their wings being naturally evolved and partially optimized for proximity flight over water surfaces. A case study was based on the A-90 Orlyonok Russian Ekranoplan, where alternative bioinspired wing variations were proposed. The study objective was to investigate the possible increased flight aircraft performance when using bioinspired wings, as well as verify the static and dynamic aircraft stability compliance for Ground-Effect flight. The methodology presented herein along with the study results, provided an incremental step towards advancing Ground-Effect aircraft conceptual designs using computational fluid dynamics.

Aerodynamic performance of semi-wing with multiple winglets operating at low- and medium-range Reynolds numbers

Birds have traits that can induce better aerodynamic efficiency along with high manoeuvring capability during its flight, which could be shared with unmanned aerial vehicles for improving their aerodynamic performances. One such feature of the wing tip, i.e. the primary feathers of the birds could be an effective geometrical feature to reduce the wing tip vortices. This paper presents the bio-inspired wing tip devices, i.e. three-and four-tipped multiple winglets in reducing the strength of vortices emanating from the wing tip of the wing operating in the Reynolds number (Re) of [Formula: see text] and [Formula: see text]. Different combinations of both three- and four-tipped multiple winglets have been designed by varying the cant angle of each tip. Numerical simulations were carried out using Ansys-Fluent by solving three-dimensional Reynolds averaged Navier–Stokes formulations coupled with k-[Formula: see text] turbulence model to resolve the features of tip vortices. The simulation clearly indicates that there is a strong correlation between the size of the vortices and the aerodynamic performance parameters such as [Formula: see text], [Formula: see text] [Formula: see text], [Formula: see text]. The three- and four-tipped multiple winglets are effective in reducing vortex drag by disintegrating large strength vortex which occurs in the tip of straight wing, into few numbers of small strength vortices. When compared to straight wing, three-tipped multiple winglet with the cant angle combination of 50, 30, 10 improves the aerodynamic efficiency by 22% to 23% and the four-tipped winglet with the cant angle combination of 60, 50, 40, 30 enhances the same by 21% to 22% in the Re of [Formula: see text]. Even the longitudinal static stability has seen considerable improvement for four-tipped multiple winglets than three-tipped multiple winglets and straight wing.

A NEW BIO-INSPIRED WING DESIGN WITH 3D ADDITIVE MANUFACTURING SCANNING AND PRINTING METHOD: MJF TECHNOLOGY

In this study, unlike many wing profiles currently available, a new wing design has been carried out with bio-inspiration, which has attracted the attention of many scientists. There are many traditional methods in 3d additive manufacturing technologies. There are several types of 3D printing method. The four most preferred 3d printing methods are as follows. Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), Multi Jet Fusion (MJF). MJF technology, one-to-one prototype production of wings with very small dimensions and aerodynamic structure has been achieved. In contrast to FDM and other additive printing technologies, it is possible to eliminate highly sensitive and high surface quality products.

Numerical Study on Aerodynamic and Aeroacoustic Performances of Bioinspired Wings

Noise control has become one of the key issues to be considered in modern aeronautical machinery design. Many efforts have been devoted to noise reduction of airfoils and wings, including traditional flow control methods. In fact, some animals in wild nature exhibit superior aerodynamic and aeroacoustic performance, providing novel ideas for solving this engineering problem. In this research, bionic technology is used to obtain quiet and efficient wing. Inspired by the owl’s wing, we propose two bionic configurations, one coupled with leading edge waves and trailing edge serrations. The Large Eddy Simulation and the Ffowcs-Williams and Hawkings equation is applied to simulate the aerodynamic and aeroacoustic characteristics of wings at low-Reynolds number flow. Numerical results demonstrate that the bioinspired wings have excellent aerodynamic performances and remarkable lower overall sound pressure level compared to NACA 0016 which has similar relative thickness. In addition, the unsmooth structure of leading edge waves and trailing edge serrations provide an additional 4.27 dB noise suppression effect, with little impact on aerodynamic characteristics at small angle of attack. The detailed analysis reveals that, due to the special owl-based profile, the flow around two bioinspired wings is mainly turbulent on the upper and lower surfaces, and no laminar separation bubble is detected at the trailing edge. Moreover, the unsmooth structure modifications successfully weaken the scale and scope of coherent vortex structures. These factors contribute to reducing the associated pressure fluctuation, thereby controlling the aeroacoustic noise of wing. Consequently, a coupled bionic wing is presented with the excellent aerodynamic and aeroacoustic characteristics. The conclusions are envisioned to be beneficial to the design of new generation low-noise aeronautical machinery.

Bio-inspired generative design for engineering products: A case study for flapping wing shape exploration

Nature has undergone millions of years of evolution, enabling organisms to adapt and survive in their environment. The remarkable features developed by these organisms serve as a rich source of inspiration for designers involved in engineering design. However, the effective application of bio-inspired design faces challenges due to the gap between biology and engineering, as well as the limited level of design automation. This paper proposes a bio-inspired generative design framework (BIGD), containing three main steps of dataset building, generator modeling, and design evaluation, which aims to automatically produce innovative designs by synthesizing a diverse range of natural designs using deep generative models. Specifically, a computational workflow is established for automated bio-inspired wing shape synthesis. The process of constructing a dataset typically involves web crawling data from various sources, followed by data preprocessing to ensure clarity. The data is then structured with prior knowledge from the biological domain and outliers are excluded. Finally, design knowledge is extracted through data mining and knowledge extraction techniques. In the case of a flapping wing shape design, the deep generative model is constructed using a bird wing dataset created with a strong foundation in biological domain knowledge. The wings generated by BIGD exhibit superior lift performance across a range of working conditions, showcasing the advantages of using BIGD to directionally guide the evolution of generative models based on biological knowledge. This research highlights the potential of using computational methods in bio-inspired design to rapidly generate innovative and high-performance designs.

Neural-Inspired Measurement Observability

The neural encoding by biological sensors of flying insects, which prefilters stimulus data before sending them to the central nervous system in the form of voltage spikes, enables sensing capabilities that are computationally low cost while also being highly robust to noise. This process, which can be modeled as the composition of a linear moving average filter and a nonlinear decision function, inspired the work reported here to improve engineered sensing performance by maximizing the observability of particular neural-inspired composite measurement functions. We first present a tool to determine the observability of a linear system with measurement delay (the first element of the composition), and then use a Lie algebraic observability approach to study nonlinear autonomous systems with output delay (the second element of the composition). The Lie algebraic tools are then extended to address overall observability of systems with composite outputs as in the neural encoder model we adopt. The analytical outcomes are supported using the empirical observability Gramian, and optimal sensor placement on a bioinspired wing model is performed using metrics based on the empirical Gramian.

Unsteady flow control mechanisms of a bio-inspired flexible flap with the fluid–structure interaction

Recently, the development of bio-inspired aircrafts has broad application prospects. However, the flow separation in the boundary layer of the bio-inspired wing under low Reynolds number becomes a great challenge for the design of a novel bio-inspired aircraft. It is worth noting that birds in nature can easily control flow separation, thanks to the flap-like flexible plumes attached to their wing surfaces. In this paper, the unsteady flow control of the flexible flap is studied by the immersed boundary-lattice Boltzmann-finite element method (IB-LB-FEM). The mechanism of flow separation on the airfoil surface at a bio-inspired large angle of attack (AOA) is suggested. The effects of the flexible flap position and its material properties on the unsteady flow control of the airfoil at large AOA are systematically discussed. The deformation law of the flexible flap with fluid–structure interaction (FSI) is revealed, and its influence on unsteady aerodynamics of the airfoil is discussed. The results show that with the increase in the AOA, the aerodynamic characteristics of the airfoil change with time from “periodic state” to “chaotic state” to “quasi-periodic state,” which is closely related to the unsteady flow separation on the airfoil upper surface. The new induced vortex is formed at the end of the flexible flap because of the FSI, which enhances or weakens the strength of vortices on the airfoil surface, affecting the aerodynamics of the airfoil. The flow control mechanism of the flexible flap proposed in this paper will provide a new design idea for the novel bio-inspired aircraft.

A Novel Actuation Strategy for an Agile Bioinspired FWAV Performing a Morphing-Coupled Wingbeat Pattern

Flying vertebrates exhibit sophisticated wingbeat kinematics. Their specialized forelimbs allow for the wing morphing motion to couple with the flapping motion during their level flight, Previous flyable bionic platforms have successfully applied bio-inspired wing morphing but cannot yet be propelled by the morphing-coupled wingbeat pattern. Spurred by this, we develop a bio-inspired flapping-wing aerial vehicle (FWAV) entitled RoboFalcon, which is equipped with a novel mechanism to drive the bat-style morphing wings, performs a morphing-coupled wingbeat pattern, and overall manages an appealing flight. The novel mechanism of RoboFalcon allows coupling the morphing and flapping during level flight and decoupling these when maneuvering is required, producing a bilateral asymmetric downstroke affording high rolling agility. The bat-style morphing wing is designed with a tilted mounting angle around the radius at the wrist joint to mimic the wrist supination and pronation effect of flying vertebrates' forelimbs. The agility of RoboFalcon is assessed through several rolling maneuver flight tests, and we demonstrate its well-performing agility capability compared to flying creatures and current flapping-wing platforms. Wind tunnel tests indicate that the roll moment of the asymmetric downstroke is correlated with the flapping frequency, and the wrist mounting angle can be used for tuning the angle of attack and lift-thrust configuration of the equilibrium flight state. We believe that this work yields a well-performing bionic platform and provides a new actuation strategy for the morphing-coupled flapping flight.

High-Performance Morphing Wing for Large-Scale Bio-Inspired Unmanned Aerial Vehicles

This letter proposes a novel bio-inspired wing design to improve some characteristics of Flapping Wing Unmanned Vehicles (FWUV) related to their potential applications such as payload capability, maneuverability, low injury risk, and energy improvement. The suggested solution takes advantage of a broadly based avian research, focusing on the integration of advanced bird-like features ranging from bird-like high-compliant airfoil to active morphing strategies to mimic the ways birds naturally manage flights. The proposed conceptual design is supported by Unsteady Vortex Latex Method simulations provided by a novel flapping-oriented open-source solver. Prototype validation relies on both test-bench and real-flights results. A motion capture system is used to validate the wing aero-elastic characteristics. The resulted improvements are highlighted by a comprehensive comparison with different similar-size prototypes.

Aerodynamic performance characterization of bio-inspired wings with leading edge tubercles at low Reynolds number

On the observation of biomimetic Humpback Whale (HW) flippers, the airfoil aerodynamic performance characteristics are explored. The Leading Edge (LE) tubercle geometry was inspired by the flipper of HW that has rounded LE protuberances and tapered trailing edge configurations. The tubercles have excellent flow control characteristics at the post-stall region. Aerodynamic characteristics of airfoils such as NACA0015 and NACA4415 with LE tubercles are experimentally and numerically investigated at the low Reynolds number about Re = 1.83 × 105. The bio-inspired modified airfoils (HUMP 0015 and 4415) are designed with the amplitude to wavelength ratio [Formula: see text] of 0.05. The numerical simulation over the modified airfoils shows that, at higher Angle of Attack the flow separation is delayed in the peak region whereas the early flow separation is observed in the trough region adjacent to the LE. The boundary layer flow separation analysis is done extensively through numerical simulations and the velocity vector profiles are captured at different chordwise positions. The stall delay phenomenon is observed through the outcome of this research that specifically insists at the peak region of tubercles. Computation of Coefficient of pressure [Formula: see text] distribution is also done by both numerical and wind tunnel experiments. Analysis of [Formula: see text] distribution allows the identification of critical regions that initiate the adverse pressure gradient and region of flow separation. It is a novel effort to predict the Coefficients of Lift [Formula: see text] and Drag [Formula: see text] concerning the bio-inspired airfoils through [Formula: see text] distribution such that the influence of flow separation and vortex distribution are characterized for the modified and baseline airfoils. Comparison of [Formula: see text], [Formula: see text], and [Formula: see text] between the baseline and modified airfoils reveal the enhanced momentum transfer characteristics of bio-inspired tubercles.

Aerodynamic performance of a bio-inspired flapping wing with local sweep morphing

Birds and bats frequently reconfigure their wing planform through a combination of flapping and local sweep morphing, suggesting a possible approach for improving the performance of micro aerial vehicles. We explore the effects of combined flapping and local sweep morphing on aerodynamic performance by employing a bio-inspired two-jointed flapping wing with local sweep morphing. The bio-inspired wing consists of inner and outer sections, which flap around the root joint (shoulder) and the midspan joint (wrist), respectively. The aerodynamic forces and the unsteady vortex structures are evaluated by numerically solving the incompressible Navier–Stokes equations. The results show that combined flapping and local sweep morphing can significantly enhance the aerodynamic performance. In particular, the average lift coefficient is 1.50 times greater than that of simple gliding with single local sweep morphing. Combined flapping and local sweep morphing also have a relatively high pitch moment and shift the aerodynamic center position backward, producing advantages in terms of maneuverability/agility and stability. We find that the vortex structures associated with the combined motion feature midspan vortices, which arise from the leading-edge vortices of the inner wing and contribute to the enhanced aerodynamic performance. We show that the kinematics of combined flapping and local sweep morphing can be further optimized if the midspan vortices are captured by the outer wing.

Fully-printed metamaterial-type flexible wings with controllable flight characteristics

Insect wings are an outstanding example of how a proper interplay of rigid and flexible materials enables an intricate flapping flight accompanied by sound. The understanding of the aerodynamics and acoustics of insect wings has enabled the development of man-made flying robotic vehicles and explained basic mechanisms of sound generation by natural flyers. This work proposes the concept of artificial wings with a periodic pattern, inspired by metamaterials, and explores how the pattern geometry can be used to control the aerodynamic and acoustic characteristics of a wing. For this, we analyzed bio-inspired wings with anisotropic honeycomb patterns flapping at a low frequency and developed a multi-parameter optimization procedure to tune the pattern design in order to increase lift and simultaneously to manipulate the produced sound. Our analysis is based on the finite-element solution to a transient three-dimensional fluid–structure interactions problem. The two-way coupling is described by incompressible Navier–Stokes equations for viscous air and structural equations of motion for a wing undergoing large deformations. We 3D-printed three wing samples and validated their robustness and dynamics experimentally. Importantly, we showed that the proposed wings can sustain long-term resonance excitation that opens a possibility to implement resonance-type flights inherent to certain natural flyers. Our results confirm the feasibility of metamaterial patterns to control the flapping flight dynamics and can open new perspectives for applications of 3D-printed patterned wings, e.g. in the design of drones with target sound.

A Bio-Inspired Wave-Energy Wing for Ocean Robot

A Bio-Inspired Wave-Energy Wing for Ocean Robot

Aerodynamic performance investigation of sweptback wings with bio-inspired leading-edge tubercles

The aerodynamic behavior of sweptback wing configurations with bio-inspired humpback whale (HW) leading-edge (LE) tubercles has been investigated through computational and experimental techniques. Specifically, the aerodynamic performance of tubercled wings with symmetric (NACA 0015) and cambered (NACA 4415) airfoils is validated against the baseline model at various angles of attack ([Formula: see text]. The [Formula: see text]/[Formula: see text] ratio of the HW flipper is strategically reduced to 0.15 for ascertaining the flow control potential of the bio-inspired wings with sweptback configuration. It is a novel effort to quantify the effect of the leading-edge protuberances on stall delay, flow separation control and distribution of streamline vortices at unique [Formula: see text]/[Formula: see text] ratio outside the thickness range of HW flipper morphology. Four tapered sweptback wing models (Baseline A, Baseline B, HUMP 0015, HUMP 4415) are used with the amplitude-to-wavelength ([Formula: see text] ratio of 0.24 and Reynolds number about [Formula: see text]. The chordwise pressure distributions are recorded at the peak, mid and trough regions of the tubercled wings through a detailed wind tunnel testing and validated with numerical analysis. Additionally, the flow characteristics over the bio-inspired surfaces have been qualitatively analyzed through the laser flow visualization (LFV) technique to reveal the influence of laminar separation bubbles (LSBs). The essential aerodynamic characteristics such as boundary layer trip delay, vortex mixing, stall delay, and flow control at different AoA are addressed through consistent experimental data. As the sweptback configuration is a primary choice for airplane wings, the improved aerodynamic characteristics of the tubercled wings can be effectively utilized for the design of novel lifting surfaces, hydroplanes and wind turbines in the near future.

Numerical and Experimental Analysis of 3D Micro-Corrugated Wing in Gliding Flight

Abstract In this study, computational fluid dynamics analysis was performed on a three-dimensional model of a Libellulidae wing to determine aerodynamic performance in gliding flight. The wing is comprised of various corrugated features alongside the spanwise and chordwise directions, as well as twist. The detailed features of real 3D dragonfly wing models, including all the corrugations through both span and chord, have not been considered in the past for a detailed aerodynamic analysis. The simulations were conducted by solving the Navier-Stokes equations to demonstrate gliding performance over a range of angles of attack at low Reynolds numbers. The numerical model was validated against experimental data obtained from a fabricated corrugated wing model using particle image velocimetry. The numerical results demonstrate that bio-inspired wings with corrugations compared to flat profile wings generate more lift with lower drag, trapping the vortices in the valleys of wing corrugation leading to delayed flow separation and delayed stall. The experimental and numerical results demonstrate that the methodology presented in this study can be used to measure bio-inspired 3D wing flow characteristics, including the influence of complex corrugations on aerodynamic performance. These findings contribute to the advancement of knowledge required for designing an optimized bioinspired micro air vehicle.

One-way FSI analysis of bio-inspired flapping wings

Aerodynamics and structural dynamics of the insect wings are widely considered in flapping wing micro air vehicle (FWMAV) applications. In this paper, the aerodynamic characteristics of the three-dimensional flapping wing models mimicked from the bumblebee and hawkmoth wings are numerically investigated under steady flow conditions. This study aims to simulate the one-way fluid-structure interaction (FSI) of these bio-inspired wings by transferring the aerodynamic load obtained from the computational fluid dynamics (CFD) into the finite element method (FEM) solver as a pressure load. The static aeroelastic responses of the wings under the pressure load are compared for different materials, namely, cuticle, aluminium alloy, and titanium alloy at various angles of attack (α = 0°-90°). CFD analysis shows that the hawkmoth wing model at α = 5° has the highest lift-to-drag ratio (L/D). FSI analysis demonstrates that the cuticle hawkmoth wing model at α = 90° undergoes the highest tip deflection.