Aerodynamic Performance Of Aircraft Research Articles

Influence of Double-Ducted Serpentine Nozzle Configurations on the Interaction Characteristics between the External and Nozzle Flow of Aircraft

To clarify the influence of the serpentine nozzle configurations on the flow characteristics and aerodynamic performance of aircraft, the flow features and aerodynamic performances of the double-ducted serpentine nozzles with different aspect ratios (AR), length–diameter ratios (LDR) and shielding ratios (SR) are numerically investigated. The results show that the asymmetric nozzle flow occurs due to the curved profile of serpentine nozzles, and a local accelerating effect exists at the S-bend, causing the increase in wall shear stress. The unilateral unsymmetrical expansion of the tail jet in the upward direction interacts with the separated external flow of the afterbody, forming an obvious cross-shock wave and shear layer structure. The surface pressure of the afterbody increases along the external flow direction, and decreases sharply in the separation point of the boundary layer. With the increase in AR and LDR, the local accelerating effect of the nozzle flow weakens, while with the increase in SR, the accelerating effect increases. The total pressure recovery coefficient, flow coefficient and axial thrust coefficient all decrease with the increase in AR, LDR, and SR. The thrust vector angle decreases with the increase in AR but is less affected by LDR and SR.

A coupled FEM-FFT concurrent multiscale method for the deformation simulation of CFRPs laminate

Carbon fiber reinforced polymer composites (CFRPs) laminate is increasingly used in aircraft structures and its assembly deformation has great influence on the aircraft aerodynamic profile and mechanical performance. Due to the inherent multiscale nature of CFRPs, the traditional macroscopic models are unable to incorporate their true microstructural details, resulting in them being unable to provide both the macro and micro deformations simultaneously. To address this issue, this work proposed a coupled FEM-FFT concurrent multiscale method for the deformation simulation of CFRPs laminate, where the mechanical response of each macro point of CFRPs laminate was from the corresponding unidirectional representative volume element (UD RVE). The FEM (Finite Element Method) was used for the analysis at the macroscopic scale, while the FFT (Fast Fourier Transform) based method was employed in the UD RVE to speed up the calculation. The elastoplastic behavior of resin matrix in the UD RVE was modelled with the parabolic yield criterion. The proposed concurrent multiscale method was validated respectively by the tension, compression and shearing experiments of CFRPs laminate. The results show that there is a good agreement both for the full strain field and load–displacement curve, demonstrating the effectiveness of the proposed concurrent multiscale method.

Improving flight performance of UAVs by ice shape modulation

Aircraft icing poses a great threat to flight safety. In response to the characteristics of high-power consumption, large volume, and heavy weight of traditional anti-/de-icing technologies, the concept of ice shape modulation is proposed, which is called ice tolerant flight. Firstly, the flight performance of Unmanned Aerial Vehicle (UAV) was compared in three states: no ice, full ice, and modulated ice through flight tests. It was found that ice shape modulation has a significant improvement effect on the aerodynamic performance of aircraft under icing conditions. Under the three modulated ice shape conditions in this experiment, the lift coefficient of the UAV under different ice shape modulation conditions increased by 18%–33%, and the stalling angle was delayed by 3°-5°. Subsequently, the pressure distribution, streamlines in the flow field, and detached vortex distribution of the UAV model in these three states were obtained through numerical simulation, to study the mechanism of ice shape modulation on the aerodynamic performance of aircraft. The simulation found that the reason for the improvement of the wings effect after ice shape modulation is that the modulated area forms a leading-edge protrusion structure similar to a vortex generator. This structure prolongs the mixed flow region on the wings surface and reduces the trend of flow separation, which plays a role in increasing lift and reducing drag for UAVs under icing conditions. Finally, a reverse reachable set that can be used for unexpected state recovery is used as the definition of flight safety boundaries, and an aircraft dynamics model is established to obtain flight safety boundaries for different states. Research has found that the flight safety boundary of the UAV in a no ice state is greater than that in a modulated ice state, and the safety boundary in a modulated ice state is greater than that in a full ice state. Compared with the full ice state, the flight safety boundary after modulation has expanded by 27.0%. The scheme of ice shape modulation can provide a basis for the flight safety of aircraft under icing conditions.

Influence of flaps deflection angle on aerodynamic performance of aircraft

Flaps, as one of the lift-augmentation devices installed on aircraft, provide sufficient lift during takeoff and landing phases. By installing flaps on the wing, the wing area can be increased, and the wing curvature can be modified. by adjusting the position of the flaps, the aircrafts aerodynamic characteristics can be regulated. This article focuses on studying the impact of forces on trailing edge flaps during takeoff. As finding the appropriate angle of deflection is a crucial factor in improving flight efficiency, this article primarily investigates the influence of flap deflection angles on the aerodynamic forces acting on the aircraft during low-speed flight. The Flow Simulation module is utilized for the analysis of the flow field. The relation between lift and tilt angle of the flap is obtained from numerical simulations. Through the analysis, for the chosen type of flaps configuration, the optimal flap angle for takeoff is 45. This article may offer a reference for the design of flaps.

Innovative Control Effectors for Maneuvering of Air Vehicles

Flow control is a rapidly developing key technological area which is subject to extensive research as it offers the potential to enhance aircraft aerodynamic performance, control, and maneuverability. The current paper details the methods and the results of a research which envisions assisting the newly formed NATO Task Group STO-AVT-239, with assessing the ability of modern active flow control actuators to improve the performance of Unmanned Combat Air Vehicles (UCAV). The project was supported by the ACE Undergraduate Research Topics Program at IIT and investigated the feasibility of the Coanda effect in achieving Circulation Control (CC) in order to produce rolling motion in cruise. Understanding of the performance of the SACCON airframe design and the complex vortex dominated flow field around was achieved through research papers and previous work of NATO Task Groups. It was discovered that a mid-span vortex influences and disturbs the flow above the control surfaces diminishing their effectiveness. A simple freeware computer code was used to predict the behavior of the airframe and the results were compared to experiment. The predictive abilities of the code were assessed to be good given the limitations of the software. Along with the airframe, CC was researched inorder to predict its maneuver control capabilities.The experimental data and the computationalpredictions were then used in combination witha semi-empirical aileron control model to predictthe aileron effectiveness and compare it tothe CC results. In order to be able to apply forresearch funding from appropriate institutions,a windtunnel experiment was designed andplanned to be conducted to validate the developedmodel.

An Aerodynamic Equation of State—Part I: Introduction and Aerospace Applications

<div>In subsonic aircraft design, the aerodynamic performance of aircraft is compared meaningfully <i>at a system level</i> by evaluating their range and endurance, but cannot do so at <i>an aerodynamic level</i> when using lift and drag coefficients, <i>C<sub>L</sub> </i> and <i>C<sub>D</sub> </i>, as these often result in misleading results for different wing reference areas. This Part I of the article (i) illustrates these shortcomings, (ii) introduces a dimensionless number quantifying the induced drag of aircraft, and (iii) proposes an <i>aerodynamic equation of state</i> for lift, drag, and induced drag and applies it to evaluate the aerodynamics of the canard aircraft, the dual rotors of the hovering <i>Ingenuity</i> Mars helicopter, and the composite lifting system (wing plus cylinders in Magnus effect) of a YOV-10 <i>Bronco</i>. Part II of this article applies this aerodynamic equation of state to the flapping flight of hovering and forward-flying insects. Part III applies the aerodynamic equation of state to some well-trodden cases in fluid mechanics found in fluid-mechanics textbooks.</div>

An efficient flow control technique based on co-flow jet and multi-stage slot circulation control applied to a supercritical airfoil

Abstract Circulation control is a kind of efficient flow control technology which can improve aircraft aerodynamic performance and reduce fuel consumption. However, improving the aerodynamic efficiency of a circulation device to enhance flight endurance and achieve environmentally flying is a challenging problem for the application of circulation control. This paper presents an efficient flow control technique that combines co-flow jet and multi-stage slot circulation control. The combinational flow control technique is applied to a supersonic airfoil to test its energy consumption and aerodynamic benefit achievement. Results show that both the single and double slot circulation control can improve the maximum lift-drag ratio of the baseline airfoil, with an increment of 11.3% and 19.1%, respectively. Compared with the single application of co-flow jet control which can increase the lift-drag ratio of the baseline airfoil by 16.3% and extend the stall angle of attack from 6° to 8°, the combinational flow control can obtain a more significant lift-drag ratio increment by about 27.3% and eliminate flow separations at high angle of attack. The stall angle of attack can even be increased to about 10°. Additionally, the blowing efficiency of the circulation control airfoil has been comprehensively analyzed. The results show that the maximum effective lift-drag ratio and highest blowing efficiency can be achieved at a blowing coefficient of 0.00235.

Test Pilot and Airline Pilot Differences in Facing Unexpected Events

BACKGROUND: Unexpected events in flight might decrease the transparency of the flying process and weaken the pilot's perception of the current state, or even erode manipulating skills. However, during the flight test of a new or modified aircraft, to verify the boundaries of aircraft aerodynamic performance and handling stability, unexpected events may be encountered that need to be handled by the test pilot. Therefore, studying the differences between test pilots and airline pilots could help improve flight safety.METHODS: Two kinds of physiological parameters, eye blink rate and average fixation duration and task-related performance of test pilots and airline pilots, were analyzed in three abnormal scenarios. A total of 16 pilots participated. The study was carried out in an A320 flight simulator.RESULTS: The differences were significant for both test pilots and airline pilots in eye blink rate and average fixation duration. Furthermore, the reaction time of test pilots (Mean = 23.38 s) was significantly shorter than airline pilots (Mean = 42.63 s) in Unreliable Airspeed condition, and the pitch angle deviations between them were significant in both Wind Shear and Unreliable Airspeed condition.DISCUSSION: The uncertainty of environmental change could create more severe pressure and mental workload influence than actual system failure. For airline pilots, compared with test pilots, the importance of practicing manual flight should still be emphasized. Improving reactions to unexpected ambient conditions and unannounced fault status could also contribute to flight safety.Zheng Y, Lu Y, Jie Y, Zhao Z, Fu S. Test pilot and airline pilot differences in facing unexpected events. Aerosp Med Hum Perform. 2023; 94(1):18-24.

Improving aircraft aerodynamic performance with bionic wing obtained by ice shape modulation

For Unmanned Aerial Vehicles (UAVs) with limited electrical power to achieve effectively anti-/de-icing at the leading edge of the wing, a strategy of ice shape modulation was proposed. Isolated simulated ice shape pieces printed by 3D printing technology are mounted on a NACA0012 finite wing model, and its lift/drag coefficients and suction-side velocity fields are measured by the six-component force balance and the Particle Imaging Velocimetry (PIV), respectively. The ratio of the spanwise length of a single ice shape piece to chord length and the spanwise length of the non-icing area between the two adjacent single ice shape pieces are defined as dimensionless ice shape length (w/c) and dimensionless modulation ratio (w/λ), respectively. The results indicate that for a fixed w/λ, the wing lift coefficient first increases and then drops with increasing w/c, and a peak value exists when w/c is between 0.1 and 0.2. The lower the w/λ is, the higher the wing lift coefficient will be. The periodical variation of the flow separation area along the spanwise direction is attributed on the one hand to the acceleration effect of the flow field in the non-icing area which reduces the separation area, and on the other hand to the cross-flow caused by the streamwise vortices from the non-icing area to the icing area which promotes the mixing of the flow field (similar to vortex generators). The obtained modulation law is verified through flight tests and provides guidance for the use of ice shape modulation scheme for UAVs that cannot be completely anti-/de-icing under severe weather conditions.

Multipurpose distributed dielectric-barrier-discharge plasma actuation: Icing sensing, anti-icing, and flow control in one

Icing and stalling on the surfaces of aircraft wings endanger flight safety. The object of this research is a nanosecond pulsed dielectric-barrier-discharge plasma actuation unit with a distributed layout, and the aerodynamic performance of aircraft wing surfaces under icing and stalling conditions is improved by changing the plasma actuation electrical parameters. Actuated under low voltage and frequency, the unit acts as a sensor to judge icing according to the change in electrical parameters. Actuated under high voltage and frequency, the discharge is severe and generates a large amount of heat, giving rise to an anti-icing unit; anti-icing is carried out through distributed-layout plasma actuation, forming modulated ice with evenly spaced distribution, which acts as a vortex generator and lessens the deterioration of aircraft aerodynamic performance under icing conditions. Actuating under high voltage and low frequency enables flow control, delays stalling, and increases lift. The different plasma-actuation functions are realized by connecting multiple units, which offers improved aircraft survivability in complex weather conditions.

Transonic Buffet Active Control with Local Smart Skin

Transonic flight has high economic benefits, but the appearance of transonic buffet limits the flight envelope. The shock control bump currently used for transonic buffet suppression tends to degrade the aerodynamic performance of the non-buffeting state. In this study, a smart skin system is used to eliminate the fluctuating load of transonic buffet by measuring the airfoil lift coefficient as the feedback signal and adjusting the local skin height using data-driven, model-free adaptive control. Since the actuator height is dynamically adjusted only after the occurrence of transonic buffet, the smart skin can completely suppress the fluctuating load and does not affect the aerodynamic performance in the non-buffeting state. The suppression effect of the proposed smart skin on transonic buffet is verified by numerical simulation of the flow. The simulation results show that due to the introduction of closed-loop control, the fluctuating load of transonic buffet can be effectively suppressed for different positions and maximum heights of the actuator. Even when the flow state changes, the robust smart skin system can also achieve the control goal. Therefore, smart skins combining flexible materials and control technologies have the potential to effectively improve the aerodynamic performance of aircraft.

Numerical Simulation Method with Engine Power and Analysis of Jet Interaction

To explore the effects of engine jet on overall aircraft aerodynamic performance, an aerodynamic numerical simulation method and the interference effects of aircraft with wing-mounted nacelle were studied. In aspect of numerical simulation, based on isentropic flow relationship and automatic mass-flow matching method, a high-precision / high-efficiency numerical simulation of inlet and exhaust boundary conditions is achieved. The calculation result is in good agreement with the experimental values, which validates the calculation method and boundary condition treatment. Through numerical simulation, it is found that the ejection of engine jet can accelerate the air flow, reduce the lower wing pressure, enhance the upper wing shock wave and increase the pitch down moment. At the same time, the effect of jet brings blowing drag and loses the cruise efficiency. The airflow acceleration caused by the narrow channel composed of engine, wing and pylon may cause strong aerodynamic interference. It can be effectively weakened by adjusting the pylon contraction shape based on the near-field pressure distribution. In this way, the shock in the inner side of the pylon can also be eliminated.

Flow Field Study of Effect of Canard Location on Aircraft Aerodynamic Performance

AbstractThe present study investigates the flow behavior due to three different vertical canard locations on the scaled‐down model aircraft by using tuft flow visualization and boundary layer measurements. The aircraft is fabricated with wing airfoil S1223 modified and canard with N22 airfoil using laser cutting technique. Three different color tufts are pasted in wing and canard at 30%, 60%, and 90%. The assembled model is placed inside the subsonic wind tunnel with flow chord Reynolds number 3.8*106, which corresponds to 35 m s−1 of the flow velocity and zero‐degree angle of attack. The boundary layers are measured at 70% of the wing chord with 00 incidence angle at three different span locations, i.e., 30%, 60%, and 90% of the wingspan with varying vertical canard positions. The results are compared with wing alone and it is found that the high wing and high canard configuration are outperformed by providing minimum velocity gradient and hence minimum skin friction drag. The tuft flow visualization also shows the identical results as the boundary layer measurements results. The aerodynamic performance of the high wing high canard configuration is found to be promising, as the skin friction drag coefficient is found to be minimum.

Structure-Actuator Integrated Design of Piezo-Actuated Composite Plate Wing for Active Shape Control

AbstractThe aerodynamic performance of aircraft can be improved via shape morphing of wings actuated by piezoelectric material. An integrated design approach of piezo-actuated wings was developed w...

NASA concept vehicles and the engineering of advanced air mobility aircraft

AbstractNASA is conducting investigations in Advanced Air Mobility (AAM) aircraft and operations. AAM missions are characterised by ranges below 300 nm, including rural and urban operations, passenger carrying as well as cargo delivery. Urban Air Mobility (UAM) is a subset of AAM and is the segment that is projected to have the most economic benefit and be the most difficult to develop. The NASA Revolutionary Vertical Lift Technology project is developing UAM VTOL aircraft designs that can be used to focus and guide research activities in support of aircraft development for emerging aviation markets. These NASA concept vehicles encompass relevant UAM features and technologies, including propulsion architectures, highly efficient yet quiet rotors, and aircraft aerodynamic performance and interactions. The configurations adopted are generic, intentionally different in appearance and design detail from prominent industry arrangements. Already these UAM concept aircraft have been used in numerous engineering investigations, including work on meeting safety requirements, achieving good handling qualities, and reducing noise below helicopter certification levels. Focusing on the concept vehicles, observations are made regarding the engineering of Advanced Air Mobility aircraft.

Influence of propeller diameter mounted at wingtip of high aspect ratio wing on aerodynamic performance

In this paper, the propeller diameter effect on cruising characteristics of a solar-powered aircraft with a high aspect ratio wing is considered. Numerical studies were performed using a program based on the Reynolds-averaged Navier-Stokes equations for Mach numbers M=0.145 and Reynolds numbers Re = 0·3-106. Three aircraft configurations were considered: without propellers, with running two-bladed propellers with diameters of 0.22 m and 0.33 m. Numerical studies showed that the installed propeller introduces significant non-linearity into the lift curves and propeller thrust coefficient versus angle of attack curves. The propeller slipstream velocity field changes depending on the propeller advance ratio and the flow velocity, thus influencing the pressure distribution on the wing and the aircraft aerodynamic performance.

Research on the Key Technology of Propulsion Drag System Division and Performance Analysis of Turboprop-powered Aircraft

The remarkable characteristic of turboprop-powered aircraft is that its power system has great influence on the aerodynamic characteristics of the aircraft. Due to the action of turboprop slipstream, the airflow velocity after the propeller is obviously increased compared with the velocity of free flow. The turbulence caused by turboprop slipstream affects the aerodynamics of the aircraft, which in turn affects the performance of turboprop blades. In this paper, the layout characteristic and development trend of turboprop powered aircraft are briefly analysed. According to the characteristics of turboprop aircraft, a thrust/drag system division principle and interference characteristics treatment method for turboprop powered aircraft are introduced. Finally the influence of slipstream on a typical turboprop powered aircraft is analysed, It is very necessary to study the influence of propeller slipstream on aircraft aerodynamic performance in the early stage of developmental the effect of propeller slipstream on the aerodynamic characteristics of the whole aircraft is the strongest in take-off state, the influence of climbing state is weakened the influence of cruise state is the lease and the effect of slipstream effect increases with the increase of thrust.

Effects of wing flexibility on aerodynamic performance of an aircraft model

The low-speed wind tunnel experiment is carried out on a simplified aircraft model to explore the influence of wing flexibility on the aircraft aerodynamic performance. The investigation involves the measurements of force, membrane deformation and velocity field at Reynolds number of 5.4 × 104–1.1 × 105. In the lift curves, two peaks are observed. The first peak, corresponding to the stall, is sensitive to the wing flexibility much more than the second peak, which nearly keeps constant. For the optimal case, in comparison with the rigid wing model, the delayed stall of nearly 5° is achieved, and the relative lift increment is about 90%. It is revealed that the lift enhanced region corresponds to the larger deformation and stronger vibration, which leads to stronger flow mixing near the flexible wing surface. Thereby, the leading-edge separation is suppressed, and the aerodynamic performance is improved significantly. Furthermore, the effects of sweep angle and Reynolds number on the aerodynamic characteristics of flexible wing are also presented.

Conceptual design and numerical studies of active flow control aerofoil based on shape-memory alloy and macro fibre composites

ABSTRACTActive flow control for aerofoils has been proven to be an effective way to improve the aerodynamic performance of aircraft. A conceptual hybrid design with surfaces embedded with Shape-Memory Alloy (SMA) and trailing Macro Fibre Composites (MFC) is proposed to implement active flow control for aerofoils. A Computational Fluid Dynamics (CFD) model has been built to explore the feasibility and potential performance of the proposed conceptual hybrid design. Accordingly, numerical analysis is carried out to investigate the unsteady flow characteristics by dynamic morphing rather than using classical static simulations and complicated coupling. The results show that camber growth by SMA action could cause an evident rise of Cl and Cd in the take-off/landing phases when the Angle-of-Attack (AoA) is less than 10°. The transient tail vibration behaviour in the cruise period when using MFC actuators is studied over wide ranges of frequency, AoA and vibration amplitude. The buffet frequency is locked in by the vibration frequency, and a decrease of 1.66–2.32% in Cd can be achieved by using a proper vibration frequency and amplitude.

Investigation and Improvement of Pusher-Propeller Installation Effect for Flying Wing UAV

This paper presents a collaborative experimental and numerical research to investigate the influences of the installation of propeller on aircraft aerodynamic performance, and two approaches to mitigate the propeller installation effect are also analyzed. The configuration under investigation is based on a real flying wing unmanned aerial vehicle with a two-bladed pusher-propeller mounted on the aft part of its associated airframe. Reynolds-averaged Navier Stokes simulations coupled with a structured finite-volume cell-vertex based solver are applied to propeller uninstalled and installed configurations, and the numerical results are shown to be in good agreement with the experimental data. The comparative results obtained through prop-uninstalled and prop-installed cases show that the installation of the pusher-propeller leads to the decline of the maximum lift-drag ratio due to aerodynamic interactions between the propeller and airframe. Detailed analysis of the numerical results highlighted that the low pressure areas on the aft part of the airframe generated by the installation of the pusher-propeller will result in an increase of the base drag and hence a decline of the maximum lift-drag ratio. The feasibilities of center shaft extension and the modification of airframe geometry to mitigate the propeller installation effect are verified by numerical simulations, and results showed that proper propeller–airframe spacing and good designs of airframe geometry can effectively improve the flow characteristic and reduce the drag induced by propeller installation effect.