Symmetric Wing Research Articles

Study on the influence of high-temperature thermochemical nonequilibrium effects on the flow field characteristics around shaped wing

With advances in research on hypersonic vehicles, the precise simulation of the effects of thermochemical non-equilibrium has become increasingly important in their design. In light of this, this study explores the influence of high-temperature thermochemical non-equilibrium on the characteristics of the flow field around the hypersonic wings of an aircraft. We initially conducted a numerical simulation by using the model of flow through a cylinder to validate the accuracy and reliability of an 11-species gas model in representing high-enthalpy flow fields. Subsequently, a systematic analysis was conducted on the impact of thermochemical nonequilibrium effects on the temperature, pressure, and enthalpy distribution in the flow field around a symmetric diamond wing under different Mach numbers and angles of attack. The research results indicated that the deeper reason behind the differing thermochemical nonequilibrium effects in the flow field at various Mach numbers lies in the distinct distribution of enthalpy of the air components at different locations, which provided a new perspective for understanding flow field variations from the standpoint of enthalpy. It is disclosed that the thermochemical non-equilibrium significantly altered the characteristics of the flow field, particularly at high Mach numbers and angles of attack, with a significant impact on the aerodynamic parameters of both the windward and the leeward sides of the wing. Through explaining the mechanisms of thermochemical non-equilibrium under flow fields with different structures, this study provides a theoretical foundations for and a fresh perspective on the design of hypersonic vehicles.

Aerodynamic Analysis of Rigid Wing Sail Based on CFD Simulation for the Design of High-Performance Unmanned Sailboats

The utilization of unmanned sailboats as a burgeoning instrument for ocean exploration and monitoring is steadily rising. In this study, a dual sail configuration is put forth to augment the sailboats’ proficiency in its wind-catching ability and adapt to the harsh environment of the sea. This proposition is based on a thorough investigation of sail aerodynamics. The symmetric rigid wing sails NACA 0020 and NACA 0016 are selected for use as the mainsail and trailing wing sail, respectively, after considering the operational environment of unmanned sailboats. The wing sail structure is modeled using SolidWorks, and computational fluid dynamics (CFD) simulations are conducted using ANSYS Fluent 2022R1 software to evaluate the aerodynamic performance of the sails. Key aerodynamic parameters, including lift, drag, lift coefficient, drag coefficient, and thrust coefficient, are obtained under different angles of attack. Furthermore, the effects of mainsail aspect ratios, mainsail taper ratios, and the positional relationship between the mainsail and trailing sail on performance are analyzed to determine the optimal structure. The thrust provided by the sail to the boat is mainly generated by the decomposition of lift, and the lift coefficient is used to measure the efficiency of an object in generating lift in the air. The proposed sail structure demonstrates a 37.1% improvement in the peak lift coefficient compared to traditional flexible sails and exhibits strong propulsion capability, indicating its potential for widespread application in the marine field.

Preliminary Numerical Modelling of a Dynamic Spring-Mounted Wing System to Reduce the Drag of Vehicles at Higher Speeds

The dynamic behaviour of a spring-mounted symmetrical NACA0012 wing in a freestream flow of air is studied in the pre-stall region, over 0° to 12° angles of incidence. The primary aim of this work is for use within the automotive sector to reduce drag and fuel emissions. However, this work will also be of interest in the motorsport sector to improve performance, and also have some applications within the aerospace and renewable energy sectors. The general operation of the concept has previously been verified at these low angles in the pre-stall region with that of a theoretical estimation using finite and infinite wings. This paper provides a numerical solution of the same problem and is compared with the previous experimentation. At these low angles, the computations yield a dynamic response settling into a static equilibrium. The stable solutions match the start of a steady regime well, when compared with the experiment. The trends are also comparable with the experiment, but the velocities at which they occur are underestimated in the computation. The computations demonstrate a drag reduction of 59% when compared to a fixed wing, whereas the lift remains stable at a near constant value with increasing wind speed. Thence, downforce is maintained whilst drag is reduced, which will facilitate higher speeds on the straight whilst maintaining vehicle direction stability. Limitations to this proof-of-concept work are highlighted and future development work is suggested to achieve even further increases in performance.

Study on the influence mechanism of polypropylene fiber on crack propagation of concrete with existing cracks under uniaxial compression

In the process of long-term service of concrete, cracks are inevitable, especially in the state of tension and compression, the crack expansion speed is accelerating, which seriously affects the service performance of concrete, and even causes major disasters. While polypropylene fiber has remarkable cracking resistance, there is a lack of theoretical analysis on crack initiation and path expansion of concrete cracks with existing cracks during the compression process. In order to analyze the inhibitory effect of fiber on the propagation of pre-existing cracks, we performed uniaxial compression tests on concrete prisms containing pre-existing cracks. Acoustic emission technology was used to monitor each test group and obtain relevant data on the cracking process of the specimens. GDEM software was used to simulate typical test conditions, and the results were compared with the test results to further explain the mechanism of crack propagation and fiber suppression. The results show that: (1) fiber can inhibit the initiation and propagation of tension wing cracks at the existing crack tip. The higher the fiber content, the shorter the symmetrical wing cracks become. (2) With the increase of fiber content (0 ∼ 4 kg/m3), the failure mode of polypropylene fiber-reinforced concrete prismatic specimens changes from tensile failure to tensile-shear failure, and finally shear failure. (3) The crack initiation stress and peak strength of prismatic specimens first increase and then decrease with the increase of fiber content. (4) The increase of fiber content delays the crack initiation time, prolongs the time to the disappearance of the peak of the acoustic emission signal, and prolongs the total time of the failure process.

Numerical comparison between symmetric and asymmetric flapping wing in tandem configuration

Dragonflies show impressive flight performance due to their unique tandem flapping wing configuration. While previous studies focused on forewing-hindwing interference in dragonfly-like flapping wings, few have explored the role of asymmetric pitching angle in tandem flapping wings. This paper compares the aerodynamic performance of asymmetric dragonfly-like wings with symmetric hummingbird-like wings, both arranged in tandem. Using a three-dimensional numerical model, we analyzed wing configurations with single/tandem wings, advance ratios (J) from 0 to 0.45, and forewing-hindwing phase differences (ϕ) from 0° to 180° at a Reynolds number of 7000. Results show that asymmetric flapping wings exhibit higher vertical force and flight efficiency in both single and tandem wing configurations. Increasing the phase difference (ϕ) improves flight efficiency with minimal loss of vertical force in the asymmetric flapping mode, while the symmetrical flapping mode significantly reduces vertical force at a 180° phase difference. Additionally, symmetric tandem flapping wings unexpectedly gain extra vertical force during in-phase flapping. This study uncovers the flow characteristics of dragonfly-like tandem flapping wings, providing a theoretical basis for the design of tandem flapping wing robots.

Fly by Feel: Flow Event Detection via Bioinspired Wind-Hairs

Bio-inspired flexible pillar-like wind-hairs show promise for the future of flying by feel by detecting critical flow events on an aerofoil during flight. To be able to characterise specific flow disturbances from the response of such sensors, quantitative PIV measurements of such flow-disturbance patterns were compared with sensor outputs under controlled conditions. Experiments were performed in a flow channel with an aerofoil equipped with a 2D array of such sensors when in uniform inflow conditions compared to when a well-defined gust was introduced upstream and was passing by. The gust was generated through the sudden deployment of a row of flaps on the suction side of a symmetric wing that was placed upstream of the aerofoil with the sensors. The resulting flow disturbance generated a starting vortex with two legs, which resembled a horseshoe-type vortex shed into the wake. Under the same tunnel conditions, PIV measurements were taken downstream of the gust generator to characterise the starting vortex, while further measurements were taken with the sensing pillars on the aerofoil in the same location. The disturbance pattern was compared to the pillar response to demonstrate the potential of flow-sensing pillars. It was found that the pillars could detect the arrival time and structural pattern of the flow disturbance, showing the characteristics of the induced flow field of the starting vortex when passing by. Therefore, such sensor arrays can detect the “footprint” of disturbances as temporal and spatial signatures, allowing us to distinguish those from others or noise.

Design of a new sweptback wing for a future supersonic aircraftResearch on lift drag characteristics and aerodynamic analysis

In recent years, with the gradual development of the aviation industry, how to make supersonic aircraft truly used in military air defense has become a global problem. In this paper, the wing design of supersonic aircraft is studied, a swept back symmetrical wing suitable for supersonic reconnaissance aircraft is designed with reasonable aspect ratio, span length, sweep angle, thrust weight ratio and wing load. On the basis of the aerodynamic characteristics of the aircraft analyzed, the inboard electron, outboard electron, flasheron, leading edge flap and all moving tip are designed to ensure the controllability in the flight line and to maintain the balance and stability of the aircraft. The qualitative analysis of the flight performance of the wing is also performed. This paper provides a possibility for the design of supersonic aircraft in the future.

SN 2023ixf in Messier 101: Photo-ionization of Dense, Close-in Circumstellar Material in a Nearby Type II Supernova

We present UV and/or optical observations and models of SN 2023ixf, a type II supernova (SN) located in Messier 101 at 6.9 Mpc. Early time (flash) spectroscopy of SN 2023ixf, obtained primarily at Lick Observatory, reveals emission lines of H i, He i/ii, C iv, and N iii/iv/v with a narrow core and broad, symmetric wings arising from the photoionization of dense, close-in circumstellar material (CSM) located around the progenitor star prior to shock breakout. These electron-scattering broadened line profiles persist for ∼8 days with respect to first light, at which time Doppler broadened the features from the fastest SN ejecta form, suggesting a reduction in CSM density at r ≳ 1015 cm. The early time light curve of SN 2023ixf shows peak absolute magnitudes (e.g., M u = −18.6 mag, M g = −18.4 mag) that are ≳2 mag brighter than typical type II SNe, this photometric boost also being consistent with the shock power supplied from CSM interaction. Comparison of SN 2023ixf to a grid of light-curve and multiepoch spectral models from the non-LTE radiative transfer code CMFGEN and the radiation-hydrodynamics code HERACLES suggests dense, solar-metallicity CSM confined to r = (0.5–1) × 1015 cm, and a progenitor mass-loss rate of yr−1. For the assumed progenitor wind velocity of v w = 50 km s−1, this corresponds to enhanced mass loss (i.e., superwind phase) during the last ∼3–6 yr before explosion.

Experimental Study of an Asymmetric Tandem Wing Configuration for Drone Application

A low-speed wind tunnel investigation characterizing the performance of an asymmetric tandem wing is presented. Wind tunnel data were supported by numerical modeling and flow visualization. The opposing wing halves of a rectangular AR=6.23 wing were systematically shifted fore and aft along a central fuselage to yield asymmetry. The results show that the lift curve slope, minimum drag coefficient, and Oswald efficiency factor are weakly affected by asymmetry, a result supported by numerical computations. The maximum lift-to-drag ratio, however, dropped essentially linearly with increasing asymmetry, a consequence of the reduced aspect ratio of each wing half decreasing the lift coefficient for minimum drag. Comparison of the experimental results with a symmetric wing with conventional empennage suggests that an asymmetric tandem wing configuration may be a viable geometry for deployable flight vehicles such as tube-launched drones.

RANS-DES Comparison on the Numerical Modelling of a Downforce Generating Wing Moving over a Solid Surface

Present paper covers the numerical modelling of a 3D wing operating near a solid surface using Reynolds Averaged Navier Stokes (RANS) and Detached Eddy Simulation (DES). The characteristics of the flow over a wing near a surface is significantly different from the free flight. Capturing the changing aerodynamics of an object moving close to a surface have importance for flight and vehicle aerodynamics. This study aims to investigate the reliability of RANS and DES turbulence modelling approaches on the numerical solution of the challenging ground effect flow physics of the downforce generating (or inverted) wings. For this purpose, a 3D symmetrical wing moving in the close proximity of a solid surface is numerically modelled in fully turbulent flow conditions. The results show that, DES approach predicts the lift force slightly better than RANS. On the other hand, tip leakage flow capturing and the separating vortex field modelling of the DES approach is clearly superior. Comparison of velocity, vorticity and the vortex visualization results are presented for the better understanding of the performance of the two modelling approaches.

Neuro-Evolutive Modeling of Transition Temperatures for Five-Ring Bent-Core Molecules Derived from Resorcinol

Determining the phase transition temperature of different types of liquid crystals based on their structural parameters is a complex problem. The experimental work might be eliminated or reduced if prediction strategies could effectively anticipate the behavior of liquid crystalline systems. Neuro-evolutive modeling based on artificial neural networks (ANN) and a differential evolution (DE) algorithm was applied to predict the phase transition temperatures of bent-core molecules based on their resorcinol core. By these means, structural parameters such as the nature of the linking groups, the position, size and number of lateral substituents on the central core or calamitic wings and the length of the terminal chains were taken into account as factors that influence the liquid crystalline properties. A number of 172 bent-core compounds with symmetrical calamitic wings were selected from the literature. All corresponding structures were fully optimized using the DFT, and the molecular descriptors were calculated afterward. In the first step, the ANN-DE approach predicted the mesophase presence for the analyzed compounds. Next, ANN models were determined to predict the transition temperatures and whether or not the bent-core compounds were mesogenic. Simple structural, thermophysical and electronic structure descriptors were considered as inputs in the dataset. As a result, the models determined for each individual temperature have an R2 that varied from 0.89 to 0.98, indicating their capability to estimate the transition temperatures for the selected compounds. Moreover, the impact analysis of the inputs on the predicted temperatures showed that, in most cases, the presence or not of liquid crystalline properties represents the most influential feature.

The Influence of Turbulence Models on the Numerical Modelling of a 3D Wing in Ground Effect

This paper deals with the influence of different RANS turbulence models on the numerical modelling of a 3D rectangular symmetrical wing in ground effect. Travelling near a solid surface, so-called ground effect, considerably alters the aerodynamic characteristics of a wing. This paper aims to investigate the performance of the widely used eddy viscosity turbulence models while predicting the changing aerodynamic behavior due to the ground effect. Three different RANS turbulence models, realizable , SST and Spalart-Allmaras models are taken into consideration. The effectiveness of the turbulence models were tasted in comparison with the experimental data in different angles of attack and ground heights. Results reveals that, the effect of the turbulence models on the numerical accuracy of the ground effect aerodynamics calculations are related to the altitude and the angle of attack. The choice of the turbulence model becomes important when the wing travels in very close proximity to the ground and the angle of attack is low or negative. The discrepancy of the calculated results mainly comes from the pressure distribution variations on the lower side of the wing. For high angles of attack, or relatively larger ground heights, the difference between the predictions of the turbulence models become negligible.

Numerical Investigation of Variation Stroke Plane Effect on Aerodynamic Performance of a 2D Flapping Airfoil Naca 0012 in Hovering Flight

This paper presents a numerical study of the effects generated by the variation of translation plane inclination angle on the aerodynamic performance (aerodynamic forces, energy consumption, and wing flow structures). This inclination angle is called . In our work, a two-dimensional airfoil will be presented using commercial software based on the finite volumes method .The numerical simulations are carried out using the experimental results parameters. Symmetric wing flapping motions with different angles of the stroke plane inclination β in conjunction with other kinematic parameters such as oscillation amplitude and Reynolds number () are examined to investigate the influence of these parameters on the energy consumption of the profile. The governing parameters of the problem under study are: the chord of the profile , the initial angle of rotation , the oscillation amplitude ∆α, the reduced frequency, Reynolds number, flow velocity , turbulence intensity at the inlet is, translation amplitude and phase difference between the rotation and translation motion .The obtained numerical results were compared with the experimental data. Moreover, vorticity and pressure contours for different values of angle will be also presented.

Rapid Identification of Interwell Fracture-Cavity Combination Structure in Fracture-Cavity Reservoir Based on Tracer-Curve Morphological Characteristics

Rapid and effective identification of interwell fracture-cavity composite structures is a necessary prerequisite for a detailed and in-depth understanding of interwell connectivity in fracture-cavity reservoirs. Current identification methods and technologies have the problems of being large-scale and low-resolution; in view of these problems, a method is proposed for rapidly identifying interwell fracture-cavity combination structures using tracer-curve morphological characteristics (peak number and characteristics of two wings). Based on concentration models of tracer curves for an interwell single fracture/pipe/cavity, the morphological characteristics of tracer curves were researched in five different series-parallel combination modes consisting of fractures, pipes, and cavities. The tracer curves of fracture-cavity reservoirs are categorized into three types: single sharp peak, single slow peak, and multipeak. Furthermore, a matching relationship between different fracture-cavity combination structures and the morphological characteristics of tracer curves is clarified. The single-sharp-peak curve with basically symmetrical wings reflects that of an interwell single fracture/pipe; the single-slow-peak curve with a steep ascending branch and a slow descending branch (obvious trailing phenomenon) reflects that of an interwell single cavity or fracture/pipe series cavity; the multipeak curve reflects that of an interwell multifracture/pipe/cavity in parallel; according to the flow difference of each branch flow channel, they can be divided into independent multipeak and continuous multipeak forms. Taking tracer monitoring results from a well group in the Tahe oilfield as an example, field application analysis and verification were carried out. The results show that this method is simple and reliable and can provide a fast and effective means for identifying interwell fracture-cavity combination structures. Meanwhile, the research results can lay a foundation for quantitative interpretation modeling of interwell tracers in fracture-cavity reservoirs considering fracture-cavity configuration.

Design and optimization on symmetrical wing longitudinal swirl generators in circular tube for laminar flow

It is crucial to further improve the overall performance of heat exchanger tube and make it adapt to higher flux conditions. In this paper, a novel type of tube inserts, symmetrical wing longitudinal swirl generators (SWLSGs), was proposed and its thermal hydraulic performance was numerically investigated under laminar flow. The effect of four geometrical parameters (inclined angle (φ1), face angle (φ2), wing angle (φ3) and pitch (P)) was explored. The results showed the mechanisms of heat transfer augmentation for SWLSGs could be divided into two main categories. The first one was that a longitudinal swirl flow with multi-vortexes would be formed by symmetrical wings. The other one was that SWLSGs had a structure similar to a deflector, which guided the cold water in the center to scour tube wall. This study found that the variation ranges of Nu/Nu0, f/f0, and the efficiency evaluation criterion (EEC) were 5.00–10.22, 4.05–14.20, and 0.71–1.35, respectively. Both exergy destruction of heat transfer and fluid flow increased as face angle and wing angle increased, and decreased as inclined angle and pitch increased. Exergy destruction minimization principle was adopted to optimize SWLSGs. After fitting function through artificial neural network, genetic algorithm was applied to obtain the Pareto front. The physical parameters of the compromised point on the Pareto front were φ1=25.6°,φ2=142.0°, φ3=13.4°, P = 64.7 mm, and EEC = 1.26. The EEC of the highest point of the ratio of the exergy destruction of heat transfer and fluid flow (REHF) was 1.48. The present work provided a new method for multi-parameter study of tube inserts, and proved that the exergy destruction as evaluation was an effective evaluation index for design and optimization.

Numerical Simulation of Wake Vortices Generated by an A330-200 Aircraft in the Nearfield Phase

In order to overcome the typical limitation of earlier studies, where the simulation of aircraft wake vortices was essentially based on the half-model of symmetrical rectangular wings, in the present analysis the entire aircraft (a typical A330-200 aircraft) geometry is taken into account. Conditions corresponding to the nearfield phase (take-off and landing) are considered assuming a typical attitude angle of 7° and different crosswind intensities, i.e., 0, 2 and 5 m/s. The simulation results show that the aircraft wake vortices form a structurally eudipleural four-vortex system due to the existence of the sweepback angle. The vortex pair at the outer side is induced by the pressure difference between the upper and lower surfaces of the wings. The wingtip vortex is split at the wing by the winglet into two smaller streams of vortices, which are subsequently merged 5 m behind the wingtip. Compared with the movement trend of wake vortices in the absence of crosswind, the aircraft wake vortices move as a whole downstream due to the crosswind to be specific, the 2 m/s crosswind can accelerate the dissipation of wake vortices and is favorable for the reduction of the aircraft wake separation. The 5 m/s crosswind results in significantly increased vorticity of two vortex systems: the wingtip vortex downstream the crosswind and the wing root vortex upstream the crosswind due to the energy input from the crosswind. However, the crosswind at a higher speed can accelerate the deviation of wake vortices, and facilitate the reduction in wake separation of the aircraft taking off and landing on a single-runway airport.

Strength Analysis of Single-Symmetry Ratio for Single-Symmetry I-Beam

Double-symmetry I-beams are the most common beam cross-sections in structural building. Because that is simpler to design and analyze steel profiles than single-symmetry I-beams. However, with the advancement of economy, the improvement of the quality of life and the cultural standards, large-scale emergence of various large span bridges, special bridge-type landscapes and viaducts. Single symmetrical I-section is better than Double-symmetry I-section to fairly in line with demand characteristics and material economy. This study chooses different Iyc/Iy ratio sections, 0.229, 0.23, 0.3 and 0.5. Iyc/Iy =0.23 is the change point of the sudden drop of the strength of the compressed airfoil. In study, the section is divided into three sections of plasticity, inelasticity and elasticity for analysis and comparison. Considering the different section sizes. If the value of Lb for a small non-elastic interval is too large, the section with a smaller cross-section will reach the elastic interval. Taking all section conditions Lb into consideration, taking 1.4m as a section will reach the non-elastic interval, if the value of the longer Lb is too small, the section with the larger section does not reach the elastic interval. In study, 10m is taken as the section to reach the elastic interval, orientation the AISC ( 2017 ) specification is used to analyze the I-beam. Symmetrical wing plate cross-sections were increased and reduced. The strength of the cross-sections between the compressed side and the tensioned side was discussed, and a single-symmetric I-section with the best cross-sectional efficiency was proposed.

Tenors Not Sopranos: Bio-Mechanical Constraints on Calling Song Frequencies in the Mediterranean Field-Cricket

Male crickets and their close relatives bush-crickets (Gryllidae and Tettigoniidae, respectively; Orthoptera and Ensifera) attract distant females by producing loud calling songs. In both families, sound is produced by stridulation, the rubbing together of their forewings, whereby the plectrum of one wing is rapidly passed over a serrated file on the opposite wing. The resulting oscillations are amplified by resonating wing regions. A striking difference between Gryllids and Tettigoniids lies in wing morphology and composition of song frequency: Crickets produce mostly low-frequency (2–8 kHz), pure tone signals with highly bilaterally symmetric wings, while bush-crickets use asymmetric wings for high-frequency (10–150 kHz) calls. The evolutionary reasons for this acoustic divergence are unknown. Here, we study the wings of actively stridulating male field-crickets (Gryllus bimaculatus) and present vibro-acoustic data suggesting a biophysical restriction to low-frequency song. Using laser Doppler vibrometry (LDV) and brain-injections of the neuroactivator eserine to elicit singing, we recorded the topography of wing vibrations during active sound production. In freely vibrating wings, each wing region resonated differently. When wings coupled during stridulation, these differences vanished and all wing regions resonated at an identical frequency, that of the narrow-band song (∼5 kHz). However, imperfections in wing-coupling caused phase shifts between both resonators, introducing destructive interference with increasing phase differences. The effect of destructive interference (amplitude reduction) was observed to be minimal at the typical low frequency calls of crickets, and by maintaining the vibration phase difference below 80°. We show that, with the imperfect coupling observed, cricket song production with two symmetric resonators becomes acoustically inefficient above ∼8 kHz. This evidence reveals a bio-mechanical constraint on the production of high-frequency song whilst using two coupled resonators and provides an explanation as to why crickets, unlike bush-crickets, have not evolved to exploit ultrasonic calling songs.

Flying With Damaged Wings: The Effect on Flight Capacity and Bio-Inspired Coping Strategies of a Flapping Wing Robot

Insects wings are subject to wear and tear from collisions and environmental disturbances during flight. They can tolerate both symmetrical and asymmetrical wing damages while maintaining flight capability to some extent. Drawing inspiration from nature's adaptation capabilities, we investigated the consequences of wing damage on a flapping wing micro air vehicle by quantifying the changes in wing kinematics, lift generation, control torque offset, and aerodynamic damping variations in flight tests with intact and damaged wings. For the proposed vehicle, the wing damage affected the lift generation significantly. Compared to the intact wings, the damaged ones result in increased stroke angle amplitude in order to compensate for lift loss and torque imbalance, which causes an increase in power consumption accordingly. Furthermore, asymmetric damages usually require a larger amount of additional control effort for flight stabilization compared to symmetric cases. In addition, aerodynamic damping varies as the wing areas change. All these aspects pose challenges in flight control. An adaptive controller is proposed to cope with the wing damage induced detrimental effects on flight capacity. Flight tests were conducted to validate the control performance. As a result, the robot can effectively overcome such challenges even in the case of a maximum unilateral lift loss of up to $\approx$ 22%. Such a result matches the performance of hovering hawkmoths, which can handle torque asymmetry up to 22.3 $\pm$ 7.8%. To the best of our knowledge, this is the first demonstration of FWMAVs to handle significant wing asymmetry in hover flight.

Evolution of Anisotropic Arrow Nanostructures during Controlled Overgrowth

AbstractAnisotropic metal nanoparticles (NPs), such as high‐aspect‐ratio Au nanorods (NRs), play an important role for applications in photocatalysis, sensing, and drug delivery because of their adjustable plasmon resonances. Their performance for these applications can be further improved by fine‐tuning their morphologies. Achieving desired NP architectures requires insight into their formation mechanisms. Here, liquid‐phase transmission electron microscopy is used to directly follow the overgrowth of Au NR seeds into nanoarrows (NAs) with fourfold symmetric wings along the sides. Adding thiol molecules like L‐cysteine to the growth solution can lead to the formation of NAs with periodic prismatic teeth instead of the straight side wings. These observations suggest that this transition is controlled by binding of L‐cysteine to the NR surface, which in turn, slows down the metal deposition rate, switching the overgrowth from the kinetically to thermodynamically controlled process. Furthermore, simulations demonstrate that these prismatic teeth enhance the NPs’ plasmonic properties. The study describes how thiol additives control the morphological evolution of metal NPs, which is important for the fabrication of NPs with tailored shapes for a broad range of applications.