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Fixed-wing MAV with morphing wing configuration is seen as the future design requirements for more aerodynamic efficiency. Wash in twist morphing MAV wings have shown a promising ability by producing smoother lift behavior and exhibited a significant increase in lift performances. However, the wash in twist morphing wings also suffer from massive drag penalties as compared to rigid or membrane (baseline) wings. Thus, the objective of this paper is to explore the aerodynamic performances of another morphing configuration known as wash out twist morphing MAV wing with a view towards the improvement of the drag performances of morphing MAV wing. Technically, the wash out twist morphing (TM) wing has deformation characteristics which are opposite from those of the wash in morphing wing. The force execution of the wash out morphing wing is similar to the wash in wing but with reversed vector direction. The investigation was carried out based on Fluid-Structure-Interaction (FSI) simulation method. The simulation was conducted in a 3D, quasi-static linear structural model combined with a steady-state, incompressible, and turbulent flow model. Three levels of the wash out morphing force (5N, 3N, and 1N) were used here to evaluate the morphing performances together with the baseline wing models (membrane wing and rigid wing). The lift coefficient results show that the wash out TM wings produced inferior lift performances compared to the baseline wings. This is due to weak vortices interactions, which lead to substantial adverse pressure on the TM wings. Meanwhile, TM wings have slight advantages in producing better drag performances than the rigid and membrane wings. Vortices study discovered that the TM wings have a weak tip vortex formation, which subsequently induces lower drag magnitude. However, the drag advantages found on the TM wings are still unable to overcome the lift drawbacks, which in turn, reducing the overall aerodynamics efficiency performances.

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and experiment. To obtain the real deformation pattern of the flapping wing, the digital image correlation technology was used to measure the dynamic deformation of the wing. The dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic effects. The dynamic deformation data were further used to calculate the inertial forces by regarding the wing as a system of particles to take into account the wing flexibility. The temporal variation of the forces produced by the flapping wing was measured by a miniature load cell. The numerical results provide more flow details of the unsteady aerodynamics of the flapping wing in terms of vortex formation and evolution. The calculated results of the inertial forces are analyzed and compared with the CFD results which represent the aerodynamic forces. In addition, the total forces, i.e., the sum of the CFD result and inertial result, are compared with the experimental results, and an overall good agreement is obtained.

A computational study is conducted on thin flat plates to simulate flows of Reynolds numbers at 104 to provide understanding and guidance for micro air vehicles and other low-Reynolds-number airfoi...

Humans' initial desire for flight stems from the imitation of flying creatures in nature. The excellent flight performance of flying animals will inevitably become a source of inspiration for researchers. Bio-inspired flight systems have become one of the most exciting disruptive aviation technologies. This review is focused on the recent progresses in bio-inspired flight systems and bionic aerodynamics. First, the development path of Biomimetic Air Vehicles (BAVs) for bio-inspired flight systems and the latest mimetic progress are summarized. The advances of the flight principles of several natural creatures are then introduced, from the perspective of bionic aerodynamics. Finally, several new challenges of bionic aerodynamics are proposed for the autonomy and intelligent development trend of the bio-inspired smart aircraft. This review will provide an important insight in designing new biomimetic air vehicles.

In recent times, scores of innovations are taking place in the field of unmanned aerial vehicle (UAV) technology that includes continuous development of design of on-board processing, memory, storage, and communication capabilities. Since UAVs are now being used extensively in many areas of expertise that include commercial, military, civilian, agricultural, and environmental applications, it is very essential that these UAVs communicate efficiently. The communication may be of the UAV-to-UAV (U2U) type or it could be with the already existing prevalent networking infrastructures UAV-to-Infrastructure (U2I) type of communication. A new prototype is developed based on the insect flight dynamism. These insect wings are very thin membranous structure. They are subjected to many forces and follow aerodynamic flying and hovering. The current research trend on this subject is the simulation of insect wing structure and utilization to create a prototype for the development of unmanned micro air vehicles. In the present study, three flying insects such as dragon fly, cicada, and jewel beetle are selected and the wing aerodynamic parameters are analyzed by mathematical models. The comparative scanning of the data revealed that cicada wing structure is their aerodynamic characteristics may serve as a prototype. The results are discussed with relation to the base data for the flapping-wing system in micro air vehicle. In this paper, we have tried to put forward an approach that is capable of providing real-time positioning and tracking of a UAV. The approach has three parts: tracking device, backend server, and mobile app.

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.

Paper plane has a high potential to be upgraded as a Micro Air Vehicle (MAV). Due to its simplicity, paper plane offers easier design option compared to the biological inspired designs as shown in recent MAV development. However, researchers have underestimate and overlook the basic aerodynamic performance induced by these paper planes. This is due to its common usage as toys and wide range of paper plane design. Thus, the objective for current work is to analyse and compare the aerodynamics forces and its performance for selected paper plane design known as Glider, Wide Stunt Glider Plane and Stunt plane. A series of CFD simulations on each paper plane was executed by using ANSYS-CFX module. A steady state, incompressible flow Navier-Stokes equation (RANS) combined with Shear Stress Turbulence (SST) model were used in this works to solve flow problem over the paper planes. The analysis is mainly conducted to study and compare the lift coefficient (), drag coefficient ()and aerodynamic efficiency () performances for each paper planes. The results show that the Glider paper plane has managed to produce better performances in terms overall magnitude, stall angle, wider angle of attack (?) envelope and higher maximum lift coefficient magnitude compared to the other paper plane design. However, Glider paper plane has the least distributions by producing at least 14.3% larger magnitude compared to the other plane design at certain ? region. Instead, The Wide Stunt has promisingly produced better distribution by producing lower value compared to the other plane design. Based on performance, the Wide Stunt paper plane has produced better and maximum aerodynamic efficiency () magnitudes compared to the other design. Wide Stunt paper plane induced at least 6.4% better magnitude compared to the other paper plane design. Based on these results, it can be concluded that Wide Stunt paper plane has promising advantages which are very crucial for the paper plane especially during hovering operation, take-off and landing manoeuvre.

This paper analyzes the effects of propeller flow on the linear coupled longitudinal and lateral dynamics of a 150 mm wingspan fixed wing micro air vehicle (MAV). The effects propeller flow on the lift, drag, pitching moment and side force is obtained through wind tunnel tests. The aerodynamic forces and moments are modeled as a function of angle of attack, sideslip angle, control surface deflection and propeller rotation per minute. The nonlinear six degrees of freedom model is linearized about straight and constant altitude flight conditions for different trim airspeed to obtain linear coupled longitudinal and lateral state space model. The eigenvalues and eigenvectors of linear coupled longitudinal and lateral state space model are compared with and without propeller flow effects. The variation in the natural frequencies and damping ratios of short period mode, phugoid mode and Dutch roll mode are analyzed for various trim airspeed. An increase in the natural frequency is observed for phugoid mode and Dutch roll mode with propeller effects. The stability of the spiral mode is enhanced by the propeller flow and also the response of the roll subsidence mode is faster with propeller effects. Detailed analysis of eigenvalues and eigenvectors shows the importance of incorporating propeller flow in analyzing the dynamics of the MAV.

In this study, the hovering performance of contra rotating ducted rotor (CRDR) for micro air vehicle (MAV) was performed by using computational fluid dynamics technique. A rotor shape with 5-inch diameter and 4.3-inch pitch for MAV was used. Aerodynamic performance and flow structures were investigated for a single rotor (SR), Contra Rotating Open Rotor and CRDR at various operating RPMs. In case of CRDR, thrust increased by 170% compared to that of SR due to the acceleration of flow at the duct inlet, and approximately 20% thrust improvement was observed compared to CROR. Duct of the CRDR was found to produce approximately 30% of the total thrust. Because torque of rear rotor is slightly greater than that of front rotor, adjustment of RPM or rotor blade shape would be necessary for the torque cancellation. Efficiency of each system was compared based on the power loading, and it was found that CRDR configuration is the most efficient configuration to generate thrust by consuming minimum power.

To solve the attitude control problem of bird-like flapping wing micro air vehicles (FWMAVs) during automatic landing, an active disturbance rejection control (ADRC) architecture is proposed in this paper. This control scheme takes into account the attitude control of flapping, transition and gliding modes in the process of automatic landing. To verify the control effect, the aerodynamic estimation method of the flapping wing based on quasi-steady theory and the dynamics of an FWMAV in Lagrangian form are applied in the simulation. The proposed control architecture consists of two independent ADRC controllers to stabilize the attitude of the pitch and roll channels. The system disturbance and the coupling effects between channels are estimated by an extended state observer (ESO) and compensated in real time in the control output. The convergence of the ESO and ADRC is proven. Simulation results show that even if the aircraft is in different flight modes, the ADRC controller can track the target trajectory quickly and accurately. Then, to realize automatic landing in a real environment, a simplified two-stage landing trajectory is designed. A landing test is carried out on this basis. The test results show that ADRC can not only stabilize the flight attitude in flapping mode but also obtain a satisfactory control accuracy and convergence speed when the aircraft is in the transition and gliding modes, confirming its usefulness in automatic landing.

To design a flapping-wing micro air vehicle (FWMAV), the hovering flight action of a beetle species (Protaetia brevitarsis) was captured, and various parameters, such as the hindwing flapping frequency, flapping amplitude, angle of attack, rotation angle, and stroke plane angle, were obtained. The wing tip trajectories of the hindwings were recorded and analyzed, and the flapping kinematics were assessed. Based on the wing tip trajectory functions, bioinspired wings and a linkage mechanism flapping system were designed. The critical parameters for the aerodynamic characteristics were investigated and optimized by means of wind tunnel tests, and the artificial flapping system with the best wing parameters was compared with the natural beetle. This work provides insight into how natural flyers execute flight by experimentally duplicating beetle hindwing kinematics and paves the way for the future development of beetle-mimicking FWMAVs.

Recent progress in flapping-wing micro air vehicles has led to the design of the bird-like main body of a flapping-wing micro air vehicle. Inspired by the Calliope hummingbird, the main body of the flapping-wing micro aerial vehicle is designed, and modifications were made to house all the commercially available components inside the main body such as a battery, motor and camera. All the components were placed inside and the center of gravity position of the main body of bio-inspired MAV was determined. Steady and unsteady computational analysis of the main body was carried out at body angles of 8, 14, 20, 28, 38, 50, 70 and 90 degrees. The effect of change in forward velocity on aerodynamics was also studied at the body angle of 28 degrees, where the lift to drag ratio is maximum. Flow physics analysis made at different body angles shows that flow starts to separate after 50 degrees and stall accurs. Bell and semi S-shaped curves are formed when the coefficient of lift and Drag are plotted against the body angle, respectively.

An amendment to this paper has been published and can be accessed via the original article.

This paper numerically studies the aerodynamic performance of a bird-like bionic flapping wing. The geometry and kinematics are designed based on a seagull wing, in which flapping, folding, swaying, and twisting are considered. An in-house unsteady flow solver based on hybrid moving grids is adopted for unsteady flow simulations. We focus on two main issues in this study, i.e., the influence of the proportion of down-stroke and the effect of span-wise twisting. Numerical results show that the proportion of down-stroke is closely related to the efficiency of the flapping process. The preferable proportion is about 0.7 by using the present geometry and kinematic model, which is very close to the observed data. Another finding is that the drag and the power consumption can be greatly reduced by the proper span-wise twisting. Two cases with different reduced frequencies are simulated and compared with each other. The numerical results show that the power consumption reduces by more than 20%, and the drag coefficient reduces by more than 60% through a proper twisting motion for both cases. The flow mechanism is mainly due to controlling of unsteady flow separation by adjusting the local effective angle of attack. These conclusions will be helpful for the high-performance micro air vehicle (MAV) design.

An enhanced nonlinear aeroelastic-coupled-flight dynamics framework that enables the investigation of propeller aerodynamics and inertial effects on the response of a very flexible aircraft is pres...

At low Reynolds numbers, revolving wings become less efficient in generating lift for hovering flight due to the increasing adverse viscous effects. Flying insects use reciprocating revolving wings...

In this paper, the functionalities of microstructures for dragonfly wing during gliding flight are investigated. Three dragonfly-mimic airfoil-shaped wings with hybrid structures were designed and fabricated as: flat wing, zigzag-edged wing and zigzag-edged wing with pillar structure. Based on the wind tunnel experiments, the zigzag-edged wing structure significantly reduces the drag force in the gliding flight. Moreover, the drag reduction is more effective on the combination of the surface pillar and zigzag-edged structure. In addition, the zigzag-edged wing structure has less influence of Karman vortex street, and the surface pillars reduce the frictional drag and stabilized the streamline in the lower vortex region. Overall, the microstructure of the dragonfly wing is an important element in the aerodynamic study. These findings can enhance the knowledge of insect-mimic wing structure and facilitate the application of Micro Air Vehicle (MAV) in the gliding flight.

In this paper, an integrated and systematic modeling of all components and subsystems of a flapping bird robot is developed using the bond graph method. The wings kinematic is independently implemented with the aim of evaluating lateral movements of the bird and aerodynamic forces are accurately extracted by assuming quasi-steady theory. In the present dynamic model, the aeroelastic bending behavior of flexible wing of the flapping bird is revealed by the bond graph method. In this regard, three elastic bending modes and one rigid motion mode of the wing are added to the model. In the following, the performance evaluation of the flapping bird and parametric study are carried out around important quantities such as frequency, initial incidence angle, torsional stiffness, and flapping amplitude of the wings, which results in applicable and attractive consequences. As an innovation, the initial classification and presentation of the comparative characteristic curves for generating lateral forces without using an additional control surface and only based on asymmetry in the flapping kinematic using the bond graph approach is done, which is essential to perform lateral-directional maneuvers. Some important correlations are achieved, which are presented in detail in the text. As an example, the relation between lateral force and phase difference between wings is quasi-linear in a variety of velocities. Therefore, this parameter can be used as input in design of lateral control system. On the other hand, the sensitivity of the lateral force to active pitch angle is more than other quantities; as a result, such mechanism can be effectively used in rapid maneuvers. Finally, based on the presented bond graph model, it would be easily possible to study the effects of design variables, mechanical properties, geometric constraints, and specially flapping kinematics on a wide range of functional and performance indices.

The conceptual design and optimization of a tilt-rotor Micro Air Vehicle (MAV) for a well-defined mission are performed. The objective of this design cycle is to decrease the design time in order to efficiently create a functional tilt-rotor drone. A flight mission is firstly defined for a tilt-rotor MAV performing hovering and cruise flight scenarios. Secondly, a complex wing shape is chosen and modeled in order to determine the final shape. The initial shape is scaled in order to acquire an arbitrary wingspan of one meter. For the specific area and wingspan, the aspect ratio of the designed wing shape is found to be equal to 2.32. Thirdly, a constraint analysis of the MAV is performed by using an energy balance analysis for six different flight scenarios. This analysis yields the required power loading and wing loading. Fourthly, the weight of the vehicle is estimated using both statistical and computational methods. After estimating the total weight and the wing loading of the MAV, the surface of the wing is determined, yielding a final wingspan of 0.76 m. Subsequently, considering the total weight of the designed MAV, the needed lift coefficient is determined. Fifthly, using the lift coefficient in conjunction with XLFR5, a batch of airfoils is selected and analyzed to evaluate the aerodynamic coefficients of the wing with each airfoil. This analysis ultimately leads to the optimum airfoil being selected. Finally, design of the fuselage and tail, internal components selection, and servo-mechanisms design are carried out prior to a stability analysis. All these proposed steps are needed to design efficient and functional tilt-rotor MAVs. Keywords: Aerodynamic analysis, Sizing, Tilt-rotor MAV, VTOL, Stability

It is well documented that the lift force of hovering micro aerial vehicles can be enhanced by increasing their air-flow velocities. This is commonly accomplished using nozzles and other flow-manipulating geometries with Reynolds numbers above order 100. [1,2] However, the effects of nozzles and other geometries are not well characterized for lower Reynolds numbers within the Stokes’ regime. In general, controlled flight in low-Reynolds number conditions using conventional propulsion methods such as propellers is difficult. Instead, levitation at ultra-low Reynolds number conditions has been accomplished through other means, including photophoretically as demonstrated recently by Cortes et al. [3] and Azadi et al. [4]. These works levitated planar materials without macroscale geometric enhancements and relied strictly on the lift force created through a temperature or accommodation coefficient difference across the planar structure. In the current work, we numerically explored the feasibility of multi-scale structures operating at low-to-moderate Reynolds numbers that pair microscale photophoretic gas pumping with macroscale jet-inducing nozzles. We used ANSYS Fluent to simulate the lift forces in centimeter-scale porous membrane discs (no macroscale enhancements) and in conical nozzles created from porous membranes. Our results indicate that porous conical nozzles provide an order of magnitude lift enhancement relative to flat discs with inlet velocities as low as 10-6 m/s. In addition, we developed a semi-analytical flow model and found good agreement with the simulations. We are currently fabricating mylar structures analogous to the simulation geometries, laser machined to create porosity and adhered to lightweight frames to maintain their shape. The multi-scale structures we create will be of critical importance for exploring low-pressure environments such as Earth’s mesosphere and the Martian atmosphere. References: [1] Benedict, Moble, et al. "Experimental investigation of micro air vehicle scale helicopter rotor in hover." International Journal of Micro Air Vehicles3 (2015): 231-255. [2] Seddon, John M., and Simon Newman. Basic helicopter aerodynamics. Vol. 40. John Wiley & Sons, 2011. [3] Cortes, John, et al. "Photophoretic levitation of macroscopic nanocardboard plates." Advanced Materials16 (2020): 1906878. [4] Azadi, Mohsen, et al. "Controlled levitation of nanostructured thin films for sun-powered near-space flight." Science Advances7 (2021): eabe1127.

The flight dynamics of Micro Air Vehicles (MAVs) exhibit significant nonlinear characteristics, which cannot be ignored in simulation or analysis. In this study, a full nonlinear simulation of the flight dynamics characteristics of a fixed-wing MAV is performed. To strengthen the developed nonlinear mathematical modeling, the MAV’s mass properties and propulsion characteristics are experimentally investigated. Moreover, the aerodynamic characteristics of the designed fixed-wing MAV are experimentally measured in a wind tunnel. The experimental aerodynamics investigation includes the propeller wash effect and the same flight conditions of the MAV. These measured data are fed to the nonlinear flight dynamics model to improve its accuracy and ensure the nonlinear aerodynamics effect on the flight dynamics. The enhanced model is then validated against response experimental measurements of the MAV in the wind tunnel that is free to pitch at different control inputs and initial conditions. Furthermore, it is compared to the response of the system identification model. The nonlinear simulation and dynamic testing investigations indicate many nonlinear phenomena, such as the appearance of the limit cycle in the longitudinal flight. This paper shows that the aerodynamic center of MAV with a low aspect ratio in the low Reynolds number regime of flow can move as a response to flap deflection. The validated nonlinear mathematical model was used to evaluate the MAV’s dynamics, design and evaluate a PID controller in flight conditions similar to the MAV’s actual flying mission. Moreover, the presented model can be used for flapping-wing MAVs using time-dependent experimental measurements.

Dynamic stall is an effect frequently seen in nature and rotary wings where flow separation induces strong force oscillations. In order to simulate such phenomena, reduced-order models (ROMs) such as the LESP-modulated discrete-vortex method (LDVM) are often used whose applicability at low Reynolds number is discussed here. CFD computations with the SST were conducted to obtain the critical leading-edge suction parameter (LESP) by analyzing the skin friction coefficient distribution for the Reynolds number tested of 1,500. Results explore both symmetrical and asymmetrical plunging of a NACA0012 airfoil following a triangular velocity profile, indicating a good agreement between experimental, CFD, and LDVM computations, which makes the latter, a very efficient and adequate method to study wake configurations of oscillating airfoils at low Reynolds numbers., Grant co-sponsored by Santander-UBI BID/FE/2019. The authors also acknowledge the financial support of the Brazilian agencies: the National Council for Scientific and Technological Development – CNPq (grants #131346/2020-2 and #306824/2019-1) and the São Paulo State Research Agency – FAPESP (grants #2017/02926-9 and #2020/00326-7).

For a tandem airfoil configuration, an airfoil is placed in the wake of an upstream airfoil. This interaction affects the aerodynamic forces of the airfoils, especially the downstream one. In the present study a tandem configuration consists of an upstream pitching airfoil and a downstream stationary airfoil is investigated. This study aims to investigate the role of reduced frequency and pitch amplitude of the upstream airfoil’s motion on lift and drag coefficients of two airfoils. These two parameters play an important role in the formation of vortices. The investigation is done for Selig-Donovan 7003 (SD7003) airfoils at low Reynolds number of 30,000 using a computational fluid dynamics. Incompressible URANS equations were employed for solving the flow field. It was found that for a fixed reduced frequency of 0.5 thrust is produced on the hindfoil for a part of cycle for different pitch amplitudes from light to deep stall while for a fixed pitch amplitude at different reduced frequencies high level of thrust or drag can be produced. The reason is related to the type and intensity of vortex-blade interaction.

To investigate aerodynamic performance of Flapping Wing Micro Air Vehicle (FWMAV), it is significant to design an efficient test system for measuring aerodynamic performance of FWMAV in hovering condition. In this study, a test platform with a simple trigger device, which can synchronously obtain data including forces, wing motion and power consumption under a certain flight status of uncontrolled FWMAV, was introduced. Time-resolved forces generated by wing flapping were measured by an ATI force transducer and the wing kinematics was tracked by a high-speed camera. A customed circuit was designed for power consumption. For simple experimental operation, a low- level signal was used to trigger our system for data acquisition, data processing and data storage. A flapper with 20cm wing span, which weighs 9.37g without batteries, was tested to characterize its aerodynamic performance through this platform. Test results show that the wing flapping frequency of the flapper can almost reach 13Hz at the flapping angle of 180° producing 8.1g maximum mean lift and 0.27g maximum mean thrust, which can provide valuable references for performance improvement and validation of aerodynamic modelling of FWMAV.

Many previous studies have shown that wing corrugation of an insect wing is only structurally beneficial in enhancing the wing&rsquo, s bending stiffness and does not much help to improve the aerodynamic performance of flapping wings. This study uses two-dimensional computational fluid dynamics (CFD) in aiming to identify a proper wing corrugation that can enhance the aerodynamic performance of the KUBeetle, an insect-like flapping-wing micro air vehicle (MAV), which operates at a Reynolds number of less than 13,000. For this purpose, various two-dimensional corrugated wings were numerically investigated. The two-dimensional flapping wing motion was extracted from the measured three-dimensional wing kinematics of the KUBeetle at spanwise locations of r = (0.375 and 0.75)R. The CFD analysis showed that at both spanwise locations, the corrugations placed over the entire wing were not beneficial for improving aerodynamic efficiency. However, for the two-dimensional flapping wing at the spanwise location of r = 0.375R, where the wing experiences relatively high angles of attack, three specially designed wings with leading-edge corrugation showed higher aerodynamic performance than that of the non-corrugated smooth wing. The improvement is closely related to the flow patterns formed around the wings. Therefore, the proposed leading-edge corrugation is suggested for the inboard wing of the KUBeetle to enhance aerodynamic performance. The corrugation in the inboard wing may also be structurally beneficial.

A wind tunnel tests campaign has been conducted to investigate the aerodynamic flow around a wing morphing to be used in a micro air vehicle. Non-intrusive whole field measurements were obtained by using PIV, in order to compare the velocity and turbulence intensity maps for the modified and the original version of an adaptive wing designed to be used in a micro air vehicle. Four sections and six angles of attack have been tested. Due to the low aspect ratio of the wing and the low Reynold number tested of 6.4 &times, 104, the influence of the 3D effects has been proved to be important. At high angles of attack, the modified model prevented the detachment of the stream, increased the lift of the wing and reduced the turbulence intensity level on the upper surface of the airfoil and in the wake.

This study examines the performance of a bio-inspired micro-air vehicle’s wing planforms at a low Reynolds number. The shape of the manta ray’s wing was extracted from the real image of a manta ray and a B-spline curve was generated. The Zimmerman planform was taken as the base for the model. Using Bezier curve, the planform was extended on the sides to create two models with differing curvatures which were named Manta A and Manta B. Numerical simulations were conducted using ANSYS FLUENT 15.0 at a Reynolds number of 1×105, and the aerodynamic characteristics of the planforms were studied. It was clear from the results that the manta ray-inspired planforms provided better lift characteristics at all angles of attack between 0° and 20° when compared to the base Zimmerman planform. It can also be observed that both the manta planforms provide better CL/CD ratios by around 11–23% between angles of attack 10° and 20°.

A micro air vehicle (MAV) is a class of miniature unmanned aerial vehicles that has a size restriction and may be autonomous. Fixed-wing MAVs are very attractive for outdoor surveillance missions since they generally offer better payload and endurance capabilities than rotorcraft or flapping-wing vehicles of equal size. This research paper describes the methodology applying indicial function theory and artificial neural networks for identification of aerodynamic derivatives for fixed-wing MAV. The formulation herein proposed extends well- known aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to strake wing planforms. Using results from dynamic water tunnel tests and indicial functions approach allowed to identify MAV aerodynamic derivatives. The experiments were conducted in a water tunnel in the course of dynamic tests of periodic oscillatory motion. The tests program range was set at high angles of attack and a wide scope of reduced frequencies of angular movements. Due to a built-in propeller, the model&rsquo, s structure test program was repeated for a turned-on propelled drive system. As a result of these studies, unsteady aerodynamics characteristics and aerodynamic derivatives of the micro-aircraft were identified as functions of state parameters. At the Warsaw University of Technology and the Air Force Institute of Technology, a &ldquo, Bee&rdquo, fixed wings micro aerial vehicle with an innovative strake-wing outline and a propeller placed in the wing gap was worked. This article is devoted to the problems of identification of aerodynamic derivatives of this micro-aircraft. The result of this research was the identification of the aerodynamic derivatives of the fixed wing MAV &ldquo, as non-linear functions of the angle of attack, and reduced frequency. The identification was carried out using the indicial function approach.

Natural flight has consistently been the wellspring of many creative minds, yet recreating the propulsive systems of natural flyers is quite hard and challenging. Regarding propulsive systems design, biomimetics offers a wide variety of solutions that can be applied at low Reynolds numbers, achieving high performance and maneuverability systems. The main goal of the current work is to computationally investigate the thrust-power intricacies while operating at different Reynolds numbers, reduced frequencies, nondimensional amplitudes, and mean angles of attack of the oscillatory motion of a NACA0012 airfoil. Simulations are performed utilizing a RANS (Reynolds Averaged Navier-Stokes) approach for a Reynolds number between 8.5×10^3 and 3.4×10^4, reduced frequencies within 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the mean angle-of-attack is also studied in the range of 0º to 10º. The outcomes show ideal operational conditions for the diverse Reynolds numbers, and results regarding thrust-power correlations and the influence of the mean angle-of-attack on the aerodynamic coefficients and the propulsive efficiency are widely explored., Fundação para a Ciência e a Tecnologia e Santander-UBI, Fundação para a Ciência e Tecnologia (FCT) through the project number UIDB/50022/2020, the Grant co-sponsored by Santander-UBI BID/FE/2019 and the grant sponsored by Fundação para a Ciência e a Tecnologia 2020.04648.BD

This paper describes the design of a miniature air suction system to house a chemical sensor. It has been designed to improve the aerodynamic chemical sensing efficiency and to have a low weight since it is meant to be mounted on a micro air vehicle. The design is done around a readily available miniature axial flow fan by computational methods. A converging-diverging shape for the air suction system with the sensor disc having a central hole and mounted at the throat is proposed as good design concept. The systematic approach has led to a light weight system with high aerodynamic efficiency even under extreme flow conditions that may be caused by MAV manoeuvre or cross winds.

Recently, a novel concept of flapping Micro-Air-Vehicles (FMAVs) with four wings has been proposed, which potentially utilizes the clap-and-fling effect for lift enhancement and agile maneuvers through an adjustment of wing kinematics. However, the application of the clap-and-fling effect in the four-winged FMAVs is underexplored and the dynamic stability is still unclear. In this paper, aerodynamics and flight dynamic stability of the four-winged FMAVs are studied experimentally and numerically. Results show that the clap-and-fling effect is observed when the flapping frequency is above 18 Hz. Due to the clap-and-fling effect, the lift generation and aerodynamic efficiency are both improved, which is mainly attributed to the fling phase. Further studies show that the clap-and-fling effect becomes weaker as the wing root spacing increases and is almost absent at a wing root spacing of 1.73 chord length. In addition, a wing with an aspect ratio of 3 can increase both lift generation and efficiency due to the clap-and-fling effect. Finally, according to the dynamic stability analysis of the four-winged FMAV, the divergence speed of the lateral oscillation mode is about 4 times faster than that of the longitudinal oscillation mode. Our results can provide guidance on the design and control of four-winged FMAVs.