High Lift-drag Ratio Research Articles

Design and dry wind tunnel test of progressive flexible variable bending wing

AbstractThe deformable wing structure can change its aerodynamic shape according to the change of flight mission and flight environment, so as to obtain better lift-drag, stability and control characteristics, which is considered as one of the future research directions of aviation technology. Considering the current technology maturity and reliability, a gradient corrugated fin is designed to realise the bending deformation of the wing. The structure of the skin is optimised to keep the skin smooth during deformation. In addition, a progressive push and pull rod is proposed to drive the wing deformation, and the fluid-structure interaction simulation is carried out for the wing deformation. At the same time, the changes of wing aerodynamic characteristics under different angles of leading and trailing edges and different push rod action schemes are analysed. Finally, a dry wind tunnel simulation test of the designed progressive flexible variable bending wing is carried out. The results of fluid-structure interaction simulation and dry wind tunnel test show that the progressive flexible variable bending wing proposed in this paper has a simple and reliable structure and remarkable deformation effect. It has advantages in increasing lift and reducing drag, ensuring high lift-drag ratio and providing wing trim moment. The deformable wing dry wind tunnel test platform designed by this method is structurally reliable, easy to operate, and can accurately reflect the influence of wing deformation on its aerodynamic force, which provides a verification means for the development of the design method and the design of practical aircraft in the future.

Causal-relationship-assisted shape design optimization for blended-wing-body underwater gliders

Blended-wing-body underwater gliders (BWBUGs) are a new generation of underwater vehicles that have been successfully applied to long-range missions. It is generally recognized that shapes with a high aspect ratio have a higher lift–drag ratio (LDR) and superior fluid performance. However, the pursuit of higher LDR cannot achieve the optimal overall performance, and there are complex design factors. It is necessary but difficult to conduct a thorough examination of shape layout, energy-carrying and other issues. In this article, the layout and energy models are established, and the causal graph is used as a multidisciplinary analysis method to show the interaction between system variables. A shape design method based on surrogate models and causal graphs is proposed that incorporates knowledge into optimization by combing the information flow and finding the relationship between variables. The results show that causal-assisted optimization can mine the characteristics of variables and discover more valuable shape designs.

Analysis on aerodynamic performance of mine horizontal axis wind turbine with air duct based on breeze power generation

Developing wireless sensor networks based on breeze power generation is of great significance to promote the development of intelligent mines. In this paper, a small horizontal axis wind turbine with air duct was designed for the underground environment of coal mine. The aerodynamic performance of the wind turbine was analyzed by constructing a three-dimensional solid model of the wind turbine. The results show that under the condition of low wind speed underground, the air flow entering the air duct in the outer basin is accelerated and rectified, and the velocity near the impeller increases. The pressure value at the front end of the blade is the largest and the pressure value at the rear end of the blade is the smallest. A certain range of negative pressure zone is formed at the rear end of the impeller, which is conducive to the operation of the wind turbine. After the air flow passes through the impeller, the speed decreases and the speed is the lowest near the rotating shaft of the impeller. Inner basin: the air flow velocity increases gradually along the radial direction of the impeller centre. The pressure at the front end of the blade is greater than the atmospheric pressure, which is conducive to promoting the stability and sustainability of the wind flow and facilitating the operation of the wind turbine. When the wind speed reaches the rated wind speed of the wind turbine, the power, torque and output power of the wind turbine increase, which can provide effective power generation. Compared with other aerofoils, NACA5505 air foil has higher lift drag ratio and thrust coefficient, and is more suitable for downhole low wind environment. Compared with the wind turbine without air duct, the wind turbine with air duct has higher wind energy conversion and output power at low Reynolds number, which verifies the feasibility of the wind turbine with air duct. In the case of low incoming wind speed and no expansion of the size of the wind turbine, improve the output power of the wind turbine and meet the intrinsic safety requirements of the wind turbine. The research can provide technical support for the continuous power supply of wireless intelligent sensors in the mine environment, and provide scientific basis for mine safety production and fine management, which has long-term economic and social benefits.

Using the combined flow control accessory to the aerodynamic performance enhancement of bio-inspired seagull airfoils

An airfoil with good stability and a high lift-drag ratio can effectively improve the stability and aerodynamic performance of the wind turbine blade. Inspired by the excellent gliding performance of the seagull wings, the unique profile and structure of the seagull wings are first extracted to restructure the bionic airfoil. Then, the flow control accessory combined the bionic flap and Gurney flap is introduced to further improve the static and dynamic aerodynamic performance of bionic seagull airfoil. Under different Reynolds numbers, the effects of the combined flow control accessory on the bionic seagull airfoil are investigated using the numerical simulation method. Based on the analysis of flow fields, the flow control mechanism of the combined flow control accessory on the stall characteristics of bionic seagull airfoil is revealed. The results show that for the static stall characteristics, when the flow control accessory is applied to the bionic airfoil, the static lift coefficient of the airfoil is increased by 15% at Reynolds numbers of Re 2.0 × 105. For the dynamic stall characteristics, the lift coefficient of the airfoil is improved during the whole dynamic stall process, the maximum is increased by 13.12%, and the area of the dynamic hysteresis loop is reduced.

Study on aerodynamic performance of mine air duct horizontal axis wind turbine based on breeze power generation

AbstractThe development of wireless sensor network based on breeze power generation is of great significance to promote the development of the intelligent mine. According to the underground environment of coalmine, a small horizontal axis wind turbine with mine air duct was designed. The aerodynamic performance of the wind turbine was analyzed by constructing the three‐dimensional solid model of the wind turbine. The results show that under the condition of underground low wind speed. Outer basin: the air flow entering the air duct is accelerated and rectified, and the speed increases near the impeller. The pressure value at the front end of the blade is the largest and the pressure value at the rear end of the blade is the smallest. A certain range of negative pressure zone is formed at the rear end of the impeller, which is conducive to the operation of the wind turbine. After passing through the impeller, the speed of the air flow decreases and is the lowest near the impeller rotating shaft. Inner basin: the air flow speed gradually increases along the radial direction of the impeller center. The pressure at the front end of the blade is greater than the atmospheric pressure, which is conducive to facilitating the operation of the wind turbine. When the wind speed reaches the rated wind speed of the wind turbine, the power, torque, and output power of the wind turbine increase, which can provide effective power generation. Compared with other airfoils, NACA5505 airfoil has higher lift drag ratio and thrust coefficient. Compared with the wind turbine without air duct, the wind turbine with air duct has higher wind energy conversion and output power under the condition of low Reynolds number, which verifies the feasibility of the wind turbine with air duct.

Vertical axis wind turbine with low turbulence Fluid-driven simulation

New blade was designed by combining the advantage of sweepback and characteristic of flight trajectory. Mass and rotational inertia of turbine were calculated before using UDF and SDOF to build up the condition of fluid-driven simulation and observing the behavior of VAWT with airfoil NACA0012-800, LJY-800 and NACA23012-800. Results showed the potential of new designed airfoil and blade with better aerodynamic stability. Fluid-driven simulation gave out further suggestion that VAWT with high lift-drag ratio coefficient and power coefficient should be validated for its feasibility by fluid-driven simulation.

Shape optimization of underwater wings with a new multi-fidelity bi-level strategy

This paper proposes a new multi-fidelity bi-level optimization (MFBLO) strategy for shape designs of underwater wings. Firstly, hydrodynamic analyses of the wing planform and sections are decoupled for constructing a bi-level shape optimization frame, which includes an upper-level task merely concerning the wing planform design and several lower-level tasks only related to the section designs. By doing this, the shape design optimization gets remarkable benefits from the reduction of dimension and computational costs. Secondly, the bridge function method combined with three multi-fidelity data fusion approaches CC1, CC2, and CC3 are proposed to conduct the bi-level optimization, respectively. After comparison analyses, CC2 shows higher computational efficiency and accuracy, which is more appropriate for the bi-level shape optimization frame. Finally, compared with the single-level optimization with the fixed planform or sections and the conventional high-dimensional optimization, the proposed MFBLO needs less computation budget and gets higher lift-drag ratio, showing its outstanding advantages in handling the shape optimization of underwater wings.

A numerical and experimental study on the performance of a twisted rudder with wavy configuration

In this paper, a Wavy Twisted Rudder (WTR) is proposed to address the discontinuity of the twisted section and increase the stalling angle in comparison to a conventional full-spade Twisted Rudder (TR). The wave configuration was applied to a KRISO Container Ship (KCS) to confirm the characteristics of the rudder under the influence of the propeller wake. The resistance, self-propulsion performance, and rudder force at high angles of the wavy twisted rudder and twisted rudder were compared using Computational Fluid Dynamics (CFD). The numerical results were compared with the experimental results. The WTR differed from the TR in the degree of separation flow at large rudder angles. This was verified by visualizing the streamline around the rudder. The results confirmed the superiority of the WTR in terms of its delayed stall and high lift–drag ratio.

Maneuver control of the hypersonic gliding vehicle with a scissored pair of control moment gyros

A maneuver control approach using a scissored pair of control moment gyros is proposed to improve the penetration ability of a hypersonic gliding vehicle (HGV) with a relatively high lift-drag ratio. Then, a multivariable strong coupling nonlinear bank-to-turn dynamical model is established for the case of lateral maneuvering of an HGV equipped with a scissored pair of control moment gyros. According to the requirement of coordinated turning of the HGV in a lateral maneuver, a decoupling controller based on feedback linearization and a linear quadratic optimal algorithm is designed. Finally, the large airspace maneuvering trajectories of the HGV including S-shaped, cycloid and spiral maneuvering modes are designed by applying overload control technology. Simulations demonstrate that the designed maneuvering trajectory significantly increases the airspace range and flexibility of the vehicle. The coordinated turn control system achieves an accurate and rapid tracking of the maneuvering trajectories in large airspace.

Calculation and Analysis on Stealth and Aerodynamics Characteristics of a Medium Altitude Long Endurance UAV

This paper seeks to calculate and analyze the stealth and aerodynamics characteristics of a medium altitude long endurance (MALE) UAV. Firstly, geometry model of the UAV was established according its technical parameters by three-dimensional modeling software. In terms of electromagnetics analysis, the physical optics (PO) and the method of equivalent currents (MEC) were used as the numerical computation method, and its feasibility was verified by experiment. The main radar scattering source, scattering characteristics, polarization characteristics and RCS level were analyzed by the computation of the main components and the whole UAV under the electromagnetic bound S (3GHz) and bound X (10GHz). In terms of fluid analysis, the finite volume method was used to solve Navier-Stokes equations and the Spalart-Allmaras (S-A) turbulence model was applied to simulate the turbulence. The aerodynamics characteristics of lift, drag and pitch in the cruise state were calculated. The final result shows: the aerodynamic layout of high aspect ratio and approximate straight wing has good aerodynamic performance of high lift-drag ratio. The high aerodynamic efficiency of UAV makes for investigation or carrying out other tactical assignment with long endurance; however, the aerodynamic layout has the disadvantage in the stealth performance. Big leading edge radius of the low-speed aero foil and low sweptback angle of wing (and empennage) has mirror reflection, which make up of the important scattering source in the front direction of UAV. Large radius of curvature surface and small angle plane of fuselage has high scattering level in the side direction of UAV. These results may help the stealth design and research of UAV.

Experimental Research of Tandem-Scheme UAV Model Aerodynamic Characteristics

Abstract Tandem-wing aerodynamic scheme became widespread for tube launch UAV due to possibility of required flight performance realization under tight dimension constraints. In this work results of wind tunnel weight and visual tests of UAV model with wingspans about 1 m are presented. Model aerodynamic characteristics were defined by six-component wind tunnel balance at Mach number 0.075 and Reynolds number 187 000 calculated for one wing chord of 0.11 m. Model stagger (390, 490, 590 mm), rear wing dihedral angle (0°, -5°, -9°), forward-to-rear wingspan ratio (0.67; 0.9; 0.92; 1.24) were variable. It was determined that model is longitudinal and directional static stable, has high maximal lift-drag ratio (in range from 10.6 to 13.7) and acceptable maximal lift coefficient without flaps (from 1.05 to 1.09) and critical angle of attack (from 15.1 to 16.4°). Stagger increasing leads to zero or positive maximal lift-drag ratio increasing. If forward wing span is larger than rear wing span than stagger increasing is more effective with zero dihedral angle. If rear wing span is larger than forward wing span than stagger increasing is more effective with negative dihedral angle.

Optimization and Design for Wind Turbine Airfoil at Multiple Working Conditions Based on Genetic Algorithm

S827 wind turbine airfoil was considered as original airfoil, which was created by NREL. Linear perturbation methods were used to get new shape parameters of wind turbine airfoil. Optimization of original airfoil was carried out based on genetic algorithm and XFOIL software, which was used to get aerodynamic performance. Results shows that the lift-drag radio of optimized airfoil was remarkable improved under multiple working conditions. Aerodynamic performance of optimized airfoil was much better comparing with the original airfoil. The optimal design method for wind turbine airfoil used in this paper can be used to optimization design of high lift-drag ratio wind turbine airfoil. Engineering practical value is considered by this method and it is feasible and efficient through example.

A NEW EFFICIENT CONTROL METHOD FOR BLENDED WING BODY

The blended wing body (BWB) is the hottest one of the aerodynamic shapes of next generation airliner because of its' high lift-drag ratio, but there are still some flaws that cut down its aerodynamical performance. One of the most harmful flaws is the low efficiency of elevator and direction rudder, this makes the BWB hard to be controlled. In this paper, we proposed a new control method to solve this problem by morphing wing—that is, to control the BWB only by changing its wing shape but without any rudder. The pitching moments, rolling moments and yawing moments are plotted versus the parameters section and the wing shape in figures and are discussed in the paper. The result shows that the morphing wing can control the moments of BWB more precisely and in wider range. The pitching moments, rolling moments and yawing moments increases or decreases linearly or almost linearly, with the value of the selected parameters. These results show that using morphing wing is an excellent aerodynamic control way for a BWB craft.

Terminal open-loop control for a hypervelocity unmanned flying vehicle in the atmosphere. Part 1

An algorithm for the terminal open-loop control of a hypervelocity flying vehicle with a high lift-drag (L/D) ratio is proposed; this algorithm ensures the implementation of spatial programmed hitting trajectories steering the vehicle to the given spatial domain with required high accuracy and required conditions of approaching this domain. The algorithm is based on the a priori construction of a rational hitting trajectory and the corresponding control vector; the control vector components are the attack and bank angles. At the beginning of the terminal phase, only constraints on the individual components of the vector of initial conditions are imposed: the ranges of altitudes, velocities, and flight path angle. In addition, the requirement for the minimum admissible resolution of the onboard radar that provides informational support at the terminal phase is taken into account in the trajectory construction. Examples of programmed hitting trajectories are given that confirm the fact that the proposed algorithm for the generation of such trajectories and the corresponding attainability sets is computationally efficient.

Lift enhancement of airfoil and tip flow control for wind turbine

Two techniques that improve the aerodynamic performance of wind turbine airfoils are described. The airfoil S809, designed specially for wind turbine blades, and the airfoil FX60-100, having a higher lift-drag ratio, are selected to verify the flow control techniques. The flow deflector, fixed at the leading edge, is employed to control the boundary layer separation on the airfoil at a high angle of attack. The multi-island genetic algorithm is used to optimize the parameters of the flow deflector. The results indicate that the flow deflector can suppress the flow separation, delay the stall, and enhance the lift. The characteristics of the blade tip vortex, the wake vortex, and the surface pressure distributions of the blades are analyzed. The vortex diffuser, set up at the blade tip, is employed to control the blade tip vortex. The results show that the vortex diffuser can increase the total pressure coefficient of the core of the vortex, decrease the strength of the blade tip vortex, lower the noise, and improve the efficiency of the blade.

Non-Cylindrical Fuselage Structural Optimization of BWB Civil Aircraft

Blended-Wing-Body (BWB) civil aircraft possesses so light structure, high lift-drag ratio and low fuel burn that it has been an important topic of future civil aircraft. But internal pressure causes large bending stress instead of skin-membrane stress in BWB non-cylindrical fuselage. For 150 seats BWB fuselage, a composite 3-bay fuselage model is analyzed and two improved configurations of braced fuselage derivatives are designed in this paper. By optimization analysis, the optimized non-cylindrical fuselage structures are obtained in low bending stress and deformation condition, and optimized layer thicknesses ratio of composite material are presented. The optimization conclusions are very valuable and applicable for the fuselage structural design of BWB civil aircraft.

Optimization design study of low-Reynolds-number high-lift airfoils for the high-efficiency propeller of low-dynamic vehicles in stratosphere

Aerodynamic performance of low-Reynolds-number high-lift airfoil makes a great impact on designing a high-efficiency propeller for low-dynamic vehicles in stratosphere. At high altitude, low-Reynolds-number airfoils are supposed to have high lift-drag ratio or high endurance factor at cruising attack angle along with good stall characteristics. To design such a high-performance low-Reynolds-number high-lift airfoil, the paper established a hierarchical multi-objective optimization platform by combing direct search optimization algorithm EXTREM and airfoil flow field solver XFOIL to automatically and quickly calculate aerodynamic performance function of airfoil by computer. It provides an effective solution to multi-point design problem of low-speed low-Reynolds-number airfoil. It can be seen from the results of three typical optimization examples, the new airfoil E387_OPT2, FX63-137_OPT2 and S1223_OPT2 based on hot low-Reynolds-number high-lift airfoils (Eppler 387 airfoil, Wortmann FX63-137 airfoil and S1223 airfoil) can meet the optimization design requirements and have very good aerodynamic characteristics in both design state and non-design state. Thus, the applicability and effectiveness of hierarchical multi-objective optimization platform are verified.

Key Parameters and Conceptual Configuration of Unmanned Combat Aerial Vehicle Concept

The nature and characteristics of attack unmanned combat aerial vehicle (UCAV) are analyzed. The principles of selecting takeoff thrust-weight ratio and takeoff weight of attack UCAV are presented by analyzing the statistical data of weights for various main combat aircraft. The UCAV airborne weapons are analyzed, followed by the preliminary estimation of the payload weight. Various typical engines are analyzed and one of them is selected. Then the takeoff weight of the UCAV is determined. Based on some basic parameters and assumptions, the qualitative decomposition calculation for takeoff weight is completed. The key factors for obtaining longer endurance of aircraft with small aspect ratio configuration are found to be high lift-drag ratio and internal space. On the basis of the conclusions mentioned above, a highly blended flying-wing plus lifting body concept is proposed. According to this concept, the UCAV configuration is designed and optimized. Finally, the UCAV configuration with small aspect ratio, high lift-drag ratio, and high stealth characteristic is obtained.

Design of Waverider Configuration with High Lift-Drag Ratio

As an ideal configuration with high lift-drag ratio, the waverider has become one kind of attracted configuration for some special purposes, especially in air and space field. The main purpose of this paper is to study the design method for cone-derived waverider at Ma=6 and its basic aerodynamic characteristics, especially the improvement of the configuration for higher lift-drag ratio. The research work is finished by CFD and shows that: Firstly, the Inverse-Design method for the waverider configuration based on inviscid conical shock wave is successful. Secondly, a great improvement of the lift-drag ratio from 2.95 to 4.06 can be obtained by modifying the prototype configuration.

The domain of the scramjet

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Townend Leo H. 1999The domain of the scramjetPhil. Trans. R. Soc. A.3572317–2334http://doi.org/10.1098/rsta.1999.0433SectionRestricted accessThe domain of the scramjet Leo H. Townend Leo H. Townend Advanced Propulsion and Energy Control Systems Ltd, 3 Hawkley Hurst, Hawkley, Hants GU33 6NS, UK Google Scholar Find this author on PubMed Search for more papers by this author Leo H. Townend Leo H. Townend Advanced Propulsion and Energy Control Systems Ltd, 3 Hawkley Hurst, Hawkley, Hants GU33 6NS, UK Google Scholar Find this author on PubMed Search for more papers by this author Published:01 August 1999https://doi.org/10.1098/rsta.1999.0433AbstractAs flight speed increases into the hypersonic regime, the stagnation pressure and temperature inside the engine become so great that, for practical structures of acceptable mass, the flow must pass through the engine at supersonic, rather than subsonic, speeds, hence the term ‘scramjet’ (supersonic combustion ramjet). The classic application for the scramjet is to the long–range airliner offering extended hypersonic flight. It is also widely accepted as a possible complement to the rockets conventionally used for space launchers. This paper explores the topic of how scramjets may best be used and is the first Frederick S. Billig Lecture in Hypersonics of the International Society for Air Breathing Engines, to be given at the 14th ISABE Symposium, 5 to 12 September 1999 in Florence, Italy. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Gildfind D, Morgan R, McGilvray M and Jacobs P (2012) Simulation of High Mach Number Scramjet Flow Conditions using the X2 Expansion Tube 18th AIAA/3AF International Space Planes and Hypersonic Systems and Technologies Conference, 10.2514/6.2012-5954, 978-1-60086-931-0, Online publication date: 24-Sep-2012. Yankui W, Shuifeng Y, Dongjun Z and Xueying D (2007) Design of Waverider Configuration with High Lift-Drag Ratio, Journal of Aircraft, 10.2514/1.22669, 44:1, (144-148), Online publication date: 1-Jan-2007. Silvester T, McIntyre T and Morgan R (2007) Superorbital expansion tube tests of a caret waverider, Shock Waves, 10.1007/s00193-007-0100-3, 17:1-2, (51-63), Online publication date: 1-Aug-2007. Curran E (2001) Scramjet Engines: The First Forty Years, Journal of Propulsion and Power, 10.2514/2.5875, 17:6, (1138-1148), Online publication date: 1-Nov-2001. (2001) Table of Contents Scramjet Propulsion, 10.2514/5.9781600866609.0000.0000, (i-xxvii), Online publication date: 1-Jan-2001. This Issue01 August 1999Volume 357Issue 1759Theme Issue ‘Hypersonic aircraft: lifting re–entry and launch’ compiled by L. H. Townend Article InformationDOI:https://doi.org/10.1098/rsta.1999.0433Published by:Royal SocietyPrint ISSN:1364-503XOnline ISSN:1471-2962History: Published online01/08/1999Published in print01/08/1999 License: Citations and impact Keywordskerosene fuelsmall SSTO aerospaceplanescooled compression processexternal combustionscramjet second stagesscramjet