Lift For Flight Research Articles

Research on the aerodynamic characteristics of dragonfly leading edge.

Dragonflies are some of the most stable and maneuverable flying organisms. To explore the mechanism of how dragonfly leading edges enhance flight lift, this article conducts a detailed study on the leading edge veins and the microstructures on them of dragonfly wings. Observations have discovered the special leading edge vein and the regularly distributed microstructures on the leading edge vein. A biomimetic model has been established, and computational fluid dynamics (CFD) simulation analysis has been conducted on the biomimetic model. The analysis explores the effects of microstructure characteristics, distribution patterns, and positions on the aerodynamic characteristics of dragonfly gliding. The analysis shows that the leading edge structure influences the incoming flow, simultaneously promotes the formation of the leading edge vortex (LEV), and increases the lift-to-drag ratio by up to 4%. A wing prototype featuring biomimetic microstructures is subsequently fabricated and tested in wind tunnel experiments. Compared with a control group without leading edge structures, the airflow passing through the biomimetic structures is influenced by the shape and arrangement of these structures. The smoother transition of the leading edge vein's shape facilitates the flow of air. The microstructures primarily filter and accelerate the airflow. The spacing of the microstructures affects the stability of the airflow, thereby influencing aerodynamic performance. Additionally, the middle-row arrangement of microstructures is more beneficial for gliding conditions, while the upper-row arrangement is more advantageous for flapping conditions. These findings enhance our understanding of insect wings and advance micro aerial vehicle applications. RESEARCH HIGHLIGHTS: This study observed the leading-edge veins and microstructures of dragonfly wings in detail. Using a biomimetic model and computational fluid dynamics (CFD) simulations, it was found that these leading-edge structures promote the formation of leading-edge vortices (LEV), increasing the lift-to-drag ratio by up to 4%. Wind tunnel experiments demonstrated that wings with biomimetic microstructures significantly improved airflow smoothness and lift compared with control wings. Additionally, the arrangement of microstructures greatly affects airflow stability and aerodynamic performance, with middle-row arrangements being more beneficial for gliding and upper-row arrangements for flapping conditions. These findings enhance our understanding of insect wings and provide innovative guidance for designing efficient micro aerial vehicles.

Enhancing Longitudinal Flight Performance of Drones through the Coupling of Wings Morphing and Deflection of Aerodynamic Surfaces

In nature, gliding birds frequently execute intricate flight maneuvers such as aerial somersaults, perched landings, and swift descents, enabling them to navigate obstacles or hunt prey. It is evident that birds rely on different wing–tail configurations to accomplish a wide range of aerial maneuvers. For traditional fixed‐wing unmanned aerial vehicles (UAVs), pitch control primarily comes from the tail's elevators, while adjusting flight lift and drag involves deploying wing flaps. Although these designs ensure reliable flight, they compromise the drones’ maneuverability to maintain longitudinal stability. Therefore, the study introduces a biomimetic morphing wing UAV, and presents a pitch control strategy that simultaneously engages morphing wings, ailerons, and tail elevators. The pull‐up maneuver tests indicate that the proposed control method results in a pitch rate that is approximately 2.5 times greater than when using only the elevator control. A closed‐loop control system for the drone is also established. The closed‐loop flight experiment, which tracks a 45° pitch angle, demonstrates the effectiveness of the proposed coupled control method in adjusting the flight attitude. In addition, during cruising, the UAV employs three configurations, straight wing, forward‐swept wing, and back‐swept wing, to cater to different mission objectives and augment its flight capabilities.

Design and field test of a foldable wing unmanned aerial–underwater vehicle

AbstractThis paper presents the design and field test of a foldable wing unmanned aerial–underwater vehicle (UAUV). The vehicle can complete diving and air operations, and still have the ability of multiple trans‐medium water egress and ingress under the condition of carrying mission load during a single flight. The wings can be folded back for drag reduction in underwater sailing and water egress, and unfolded to provide lift for flight after water egress. This paper presents the major components and system design of the vehicle, including the overall structure of the vehicle, the design of the mechanism for self‐locking and quick‐folding, the design of the electrical system, the selection of the propulsion system, and analyzes the performance gains from foldable wings and foldable propellers. Then the trans‐medium field test was introduced, and the analysis and discussion were conducted for the four typical operating conditions of the vehicle, including water sailing, aerial flight, water egress and water ingress. Furthermore, the endurance performance under the corresponding operating conditions is estimated based on experimental data and the current battery energy carried. The presence of foldable wings and a large pitch angle water egress strategy reduces the thrust‐to‐weight ratio requirement for the vehicle. The results of the field tests can provide important experience and data support for the subsequent application‐oriented UAUVs.

A wind tunnel investigation of the unsteady aerodynamic characteristics of bionic flapping wings with three-dimensional complex motion

The bionic flapping wing aircraft realizes flight by imitating the structure and flapping mode of birds. In this paper, a three-dimensional composite motion aerodynamic analysis model of a bionic flapping wing is established. The diverting field and flapping wing grid are divided up using dynamic hybrid grid technology. The flow field of the flapping wing is analyzed by solving the Navier–Stokes (N–S) equation combined with the Boussinesq hypothesis. The lift of the flapping wing under different flutter frequencies and incoming wind speeds is studied under the asymmetric flutter condition. In order to verify the accuracy of the aerodynamic simulation results, a flapping-wing shrinking-ratio model prototype is made, and low-speed wind tunnel experiments are carried out to test the changes in the flight lift of the wing at different flutter frequencies and angles of attack. A comparative analysis of the wind tunnel experiment and the aerodynamic simulation results shows that when the flapping frequency (1–5 Hz) and incoming wind speed (1–5 m/s) increase, the lift force generated by the wing flapping increases. Due to the deviation between the experimental sample airfoil area and the simulated airfoil area, as well as the wing-driven fuselage vibration during the experiment, a sensor error is produced, resulting in a deviation of about 1 N between the experimental result curve and the simulation result curve. However, the aerodynamic characteristics obtained from the aerodynamic simulation analysis are basically consistent with the aerodynamic change law measured in the wind tunnel experiment.

Transient Nature of Flight and Its Impact on Thermal Management for All Electric Aircraft

Abstract High power electronics are a key component in the electrification of aircraft. Large amounts of power need to be handled onboard to generate sufficient lift for flight. The transient nature of the aircraft's mission profile produces varied loading and environmental influences, making consistent cooling and device reliability difficult to maintain. Due to limitations in weight and performance metrics, the thermal management capability becomes a key inhibiting factor in preventing adoption of all electric aircraft. Many efforts are focused on the improvement of high-powered electronics such as the inverters, batteries, and motors, but there is a need for increased focus on the implications of each improved device on the total system with regard to thermal management. To address the many concerns for thermal management within aviation, this paper will review the prevalent factors of flight and couple them to their respective challenges to highlight the overarching effort needed to successfully integrate efficient electric propulsion devices with their protective thermal management systems. A review will be combined with a brief analytical study over inverter cooling to examine the effects of various transient parameters on the device temperature of an inverter in flight. The impact of failure in the cooling systems on the shutdown process will also be examined. Both studies are tied to the motivation for examining the impacts of new and transient challenges faced by electric power systems and help signify the importance of this focus as these systems become more present and capable within the aviation industry.

Unsteady aerodynamic characteristics of a bionic flapping wing in three-dimensional composite motion

Owing to continual advances in computational fluid dynamics, simulations of fluids have emerged as an important means of analyzing the aerodynamic characteristics of flapping-wing flight. This study establishes an aerodynamic model of bionic flapping-wing flight and uses dynamic hybrid grid technology to divide its flow field and other parts. We formulate equations to control the discretized flow field and combine the Navier–Stokes equation (N–S equation) with the theory of dynamic vortices to solve the flow field of the motion of flapping wings. We analyzed the lift and drag generated by the flapping wing at different wind speeds, amplitudes, frequencies, and chordal torsion angles. The results show the following: (1) wind speed had a significant influence on the lift resistance of the flapping wing. When the wind speed was 1 m/s, the lift force was 1.544 N and increased 4.3 times to 6.636 N when the wind speed was 5 m/s. The resistance increased from 0.39 to 0.88 N. (2) Changes in the amplitude of flutter had little effect on the average lift resistance. When the amplitude was increased from 15° to 45°, the lift force increased to only 0.757 N and drag changed by little. (3) The increase in the flapping frequency improved flight lift. When the frequency was increased from 1 to 5 Hz, the lift increased by 2.9 N (1.78 times) and resistance increased by only 0.08 N. (4) Increasing the chord torsion angle increased flight lift. The lifts at β = 5° and 15° were 6.636 and 6.654 N, respectively, 0.85 and 0.87 N greater than those at β = 0°. As the torsion angle continued to increase, the lift decreased, while the resistance increased more quickly. When β = 15°, the resistance increased by 1.53 N, 9.6 times larger than that at 0°. Increasing the flight speed and flapping frequency can increase flight lift. A small increase in the chord torsion angle increased flight lift, but an excessively large angle led to a substantial increase in drag. Increasing the amplitude of flapping can increase the instantaneous lift generated but has a smaller effect on the average lift. By revealing the influence of different parameters on the lifting resistance of a flapping wing during flight, this paper provides a theoretical foundation for the design and control of bionic flapping-wing aircraft.

Numerical simulation of unsteady aerodynamic characteristics of the three-dimensional composite motion of a flapping wing based on overlapping nested grids

Numerical simulations of the unsteady aerodynamic characteristics of the flapping wing composite motion are performed. To avoid negative grid sizes arising with the use of a dynamic grid and leading to divergences in the simulation and to errors in the results, an overlapping nested grid is used for the flow field background, wing, and fuselage structure. The analysis is based on the Navier–Stokes equations (N-S) and the pressure–velocity coupling method, while spatial dispersion is handled using the second-order finite volume and the adaptive step size solving strategy. The lift and resistance generated by the wing for different combinations of flow velocity, flutter frequency and amplitude, and torsion angle are determined, and the aerodynamic efficiency and flow fields are compared to find the flapping parameters that give the best aerodynamic efficiency. The simulation results show that the aerodynamic lift of a flapping wing can be greatly increased by increasing the flapping frequency, while, for a fixed frequency, the lift can be further increased by increasing the flapping amplitude, although by only a small amount. Increasing the torsion angle in the flapping of the wing can also increase the lift, but the aerodynamic efficiency will be reduced if this angle is too large. Thus, an appropriate selection of flapping wing motion parameters can effectively increase the flight lift and improve the aerodynamic efficiency.

Design of a hydraulically-driven bionic folding wing.

Membranous hind wings of the beetles can be folded under the elytra when they are at rest, and rotate and lift the elytra up only when they need to fly. This characteristic provides excellent flying capability and good environment adaptability. Inspired by the beetles, the new type of the bionic folding wing for the flapping wing Micro Air Vehicle (MAV) was designed. This flapping wing can be unfolded to get a sufficient lift in flight, and can be folded off flight to reduce the wing area and risk of the wing damage. The relationship between the internal pressures of the hydraulic system for the bionic wing folding varies and temperature was analyzed, the results show that the pressure within the system tends to increase with temperature, which proves the feasibility of the schematic design in theory. Stress analysis of the bionic wing was conducted, it was shown that stress distributions and deformation of the bionic wing under the positive and negative side loading are basically the same, which demonstrates that the strength of the bionic folding wing meets the requirements and further proves the feasibility of the schematic design.

Design considerations and practical results with long duration systems for manned world flights

This paper describes development of three balloon types by the author, all proposed for piloted flights around the world. The first was a superpressure pumpkin used to cross Australia. However, the balloon took up an incorrect shape when inflated. Because of this and other problems, the pumpkin was abandoned and the author built a combined helium-hot air balloon. This in turn was abandoned because it was cumbersome and costly. The author then developed an entirely new system, carrying cryogenic liquid helium to create lift in flight. Two very successful 24-h flights were made. In addition several inventions were developed for crew safety. Perhaps the most important is an entirely new way to protect pilots against sudden cabin pressure loss, with potentially broad use.

Design considerations and practical results with long duration systems for manned world flights

This paper describes development of three balloon types by the author, all proposed for piloted flights around the world. The first was a superpressure pumpkin used to cross Australia. However, the balloon took up an incorrect shape when inflated. Because of this and other problems, the pumpkin was abandoned and the author built a combined helium-hot air balloon. This in turn was abandoned because it was cumbersome and costly. The author then developed an entirely new system, carrying cryogenic liquid helium to create lift in flight. Two very successful 24-h flights were made. In addition several inventions were developed for crew safety. Perhaps the most important is an entirely new way to protect pilots against sudden cabin pressure loss, with potentially broad use.

Sexual dimorphism in the pyrgomorphid grasshopper Phymateus morbillosus: from wing morphometry and flight behaviour to flight physiology and endocrinology

Abstract In the field, adult males of the grasshopper Phymateus morbillosus are able to fly for up to 1 min and cover up to c. 100 m, whereas females, although fully winged, are apparently unable to get airborne. Morphometric data indicate that the males are lighter, have longer wings, a higher ratio of flight muscles to body mass, and a lower wing load value than females. It was investigated whether this inability of females to fly is related to fuel storage, flight muscle enzymatic design and/or the presence and quantitative capacity of the endocrine system to mobilize fuels. In both sexes, readily available potential energy substrates are present in the haemolymph in similar concentrations, and the amount of glycogen in flight muscles and fat bodies does not differ significantly between males and females. Mass‐specific activities of the enzymes GAPDH (glycolysis), HOAD (fatty acid oxidation) and MDH (citric acid cycle) in flight muscles are significantly lower in females compared with males, and mitochondria are less abundant in the flight muscles of females. There is no significant difference between the ability of the two sexes to oxidize various important substrates. Both sexes contain three adipokinetic peptides in their corpora cardiaca; the amount of each peptide in female grasshoppers is higher than in males.Thus, despite some differences listed above, both sexes appear to have sufficient substrates and the necessary endocrine complement to engage in flight. It seems more likely, from the morphometric data above, that the chief reason for flightlessness is that P. morbillosus females cannot produce sufficient lift for flight; alternatively, the neuronal functioning associated with the flight muscles may be impaired in females.

Visually induced height orientation of the fly Musca domestica

The visually controlled height orientation of fixed flying flies (Musca domestica) was investigated. The flight lift force measured by a transducer drives the vertical motion of a panorama. The dynamical conditions of the free flight are electronically simulated for the fly with respect to this degree of freedom of motion. In most of the experimentally investigated cases the panorama consists of a horizontally oriented narrow dark stripe on a bright background. The fly orientates with respect to the stripe, transporting it into a stable fixation position just below the equatorial plane of its compound eyes. It is experimentally demonstrated that the formalism of the linearized theory of the pattern induced flight orientation -- Poggio and Reichardt (1973a) -- can be applied to describe the height orientation of the fly. The experimental evidence concerning the simultaneous perception of stripes moving in a well defined manner in front of each of the two compound eyes is consistent with the hypothesis that the two halves of the visual system are perceptually additive.