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Optimization and analysis of winglet configuration for solar aircraft

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Chinese Journal of Aeronautics 2020年第12期33卷 3238-3252页

作者： Liang ZHANG dongli ma Muqing YANG Shaoqi WANG School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China Xi'an Modern Control Technology Research Institute Xi'an 710065China

Installing winglets can notably improve the aerodynamic performance of solar *** paper proposes a multi-constraints optimization method of winglets for solar aircraft,aiming to enhance the corresponding uninterrupted cruising *** optimization objective function is formed and is separately studied in aerodynamic and structural *** analysis shows that the winglet design parameters are restricted by four special constraints(geometry,aerodynamics,energy and stability)of solar *** optimization process is constructed on the basis of a multi-island genetic algorithm,and carried out for a 15 m wingspan solar *** the designed winglet is not as good as the traditional winglet in terms of drag and structural weight,the designed winglet provides a better 24 h cruising *** sensitivity between the objective function and the design parameters is investigated,and the winglet effects vary with respect to the wing aspect ratio(AR=10,15,19.6).The effect of the constraints is analysed quantitatively,and some basic laws are ***,the feasible design region and the possible optimal design parameters of winglets for different wing configurations are *** calculation results show that when the aspect ratio exceeds a certain value,the winglets will not benefit the aircraft.

关键词： Energy balance Lateral-directional stability Multi-constrained optimization Shading effect Solar aircraft Winglets

Dynamic simulation of aerial towed decoy system based on tension recurrence algorithm

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Chinese Journal of Aeronautics 2016年第6期29卷 1484-1495页

作者： ma dongli Wang Shaoqi Yang Muqing Dong Yongpan School of Aeronautic Science and Engineering Beihang University

Dynamic model of aerial towed decoy system is established and simulations are performed to research the dynamic characteristics of the system. Firstly, Kinetic equations based on spinor are built, where the cable is discretized into a number of rigid segments while the decoy is modeled as a rigid body hinged on the cable. Then tension recurrence algorithm is developed to improve computational efficiency, which makes it possible to predict the dynamic response of aerial towed decoy system rapidly and accurately. Subsequently, the efficiency and validity of this algorithm are verified by comparison with Kane’s function and further validated by wind tunnel *** results indicate that the distance between the towing point and the decoy’s center of gravity is suggested to be 5%–20% of the length of decoy body to ensure the stability of *** up-risen maneuver process, the value of angular velocity is recommended to be less than0.10 rad/s to protect the cable from the aircraft exhaust jet. During the turning movement of aircraft, the cable’s extent of stretching outwards is proportional to the aircraft’s angular ***, the decoy, aircraft and missile form a triangle, which promotes the decoy’s performance.

关键词： Numerical simulation Spinor Tension recurrence algorithm Towed cable Towed decoy

Effects of relative thickness on aerodynamic characteristics of airfoil at a low Reynolds number

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Chinese Journal of Aeronautics 2015年第4期28卷 1003-1015页

作者： ma dongli Zhao Yanping Qiao Yuhang Li Guanxiong School of Aeronautic Science and Engineering Beihang University

This study focuses on the characteristics of low Reynolds number flow around airfoil of high-altitude unmanned aerial vehicles（HAUAVs） cruising at low *** simulation on the flows around several representative airfoils is carried out to investigate the low Reynolds number *** water tunnel model tests further validate the accuracy and effectiveness of the numerical *** the effects of the relative thickness of airfoil on aerodynamic performance are explored, using the above numerical method, by simulating flows around airfoils of different relative thicknesses（12%, 14%, 16%, 18%）, as well as different locations of the maximum relative thickness（x/c = 22%, 26%, 30%, 34%）, at a low Reynolds number of 5 × 10^*** show that performance of airfoils at low Reynolds number is mainly affected by the laminar separation *** the premise of good stall characteristics, the value of maximum relative thickness should be as small as possible, and the location of the maximum relative thickness ought to be closer to the trailing edge to obtain fine airfoil *** numerical method is feasible for the simulation of low Reynolds number *** study can help to provide a basis for the design of low Reynolds number airfoil.

关键词： Aerodynamic characteristicsAirfoil Laminar separation Low Reynolds number Numerical simulation Relative thickness Water tunnel model tests

Adaptive-surrogate-based robust optimization of transonic natural laminar flow nacelle

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Chinese Journal of Aeronautics 2021年第10期34卷 36-52页

作者： Yuan YAO dongli ma Muqing YANG Liang ZHANG Yang GUO School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

Natural Laminar Flow(NLF)technology is very effective for reducing the skin friction drag of aircraft engine nacelle,but the aerodynamic performance of NLF nacelle is highly sensitive to uncertain working ***,it’s imperative to incorporate uncertainties into the design of NLF *** this study,for a robust optimization of NLF nacelle and for improving its efficiency,an adaptive-surrogate-based robust optimization strategy is established,which is an iterative optimization process where the surrogate model is updated to obtain the real Pareto front of multi-objective optimization problem.A case study is carried out to validate its feasibility and *** results show that the optimization increases the favorable pressure gradient region and the volume ratio of the nacelle by increasing its lip radius and reducing its maximum *** the aerodynamic robustness of the NLF nacelle is mainly determined by the lip radius,maximum diameter of nacelle and location of the maximum *** to the initial nacelle,the optimized nacelle maintains a wide range of low drag and high laminar flow ratio in the disturbance space,which extends the average laminar flow region to 21.6%and facilitates a decrease of 1.98 counts in the average drag coefficient.

关键词： Adaptive surrogate model Aerodynamic robustness Multi-objective optimization Natural laminar flow nacelle Uncertain working conditions

Elastic buckling analysis and optimization of thin-walled bamboo-like pipe beam subjected to pure bending

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Chinese Journal of Aeronautics 2024年第3期37卷 133-152页

作者： Yayun YU dongli ma Liang ZHANG Xiaopeng YANG Hao GUAN School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China

In this paper,a stiffening design imitating the bamboo node is proposed for weight reduction of the long composite pipe beam subjected to bending *** distribution of bamboo nodes can efficiently suppress the ovalization of the section,thus significantly improving the bending resistance of the *** on this principle,ring stiffeners are proposed to be fixed to the pipe beam,making the long beam equivalent to the combination of a series of short pipes that suffered less section ovalization.A database of the optimal laminate orientations for different normalized lengths is obtained through optimizations,where the discreteness of the ply count is *** on this database,weight optimizations are conducted,and the optimal designs of beams with and without stiffeners are obtained and *** comparison results show that the proposed bamboo-like stiffened beam not only regains a near-linear load–displacement relationship,but also reduces the weight by up to 16%under the same buckling *** addition,it is found that for the pipe beams with radius-to-thickness ratios of more than 18,increasing the radius leads to a decrease in elastic buckling resistance when the weight remains a constant,which is opposite to the design for strength and *** model and database developed in this paper can provide a reference for weight reduction design and weight estimation for composite pipe beams.

关键词： Composite beam Buckling Thin-walled structure Unmanned aerial vehicles Bamboo

Optimization and analysis of composite sandwich box beam for solar drones

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Chinese Journal of Aeronautics 2021年第10期34卷 148-165页

作者： Liang ZHANG dongli ma Muqing YANG Xinglu XIA Yuan YAO School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

Solar drones have garnered considerably research attention in recent years due to their continuous cruising capability,and the feasibility of design schemes is sensitive to the weight of *** box beam composed of carbon fiber and polymethacrylimide(PMI)foam is conducive to realize the lightweight of *** this study,a two-stage optimization design methodology for sandwich box beam is *** methodology is primarily based on a low-order analytical method for evaluating stress/deflection and the linear buckling analysis method combined with experimental correction factor for predicting the buckling ***,a case study was conducted using an 18-m wingspan solar drone,where the results of mechanical test verified the optimization *** validating the use of sandwich box beam in solar drones of other scales,additional analysis was conducted based on three aspects:(A)effects of stiffness and stability constraints on the design of sandwich box beam;(B)crucial role of the weight of foam inter layer and application scope of sandwich box beam;(C)best method to improve the buckling eigenvalue of sandwich box ***,the methodology and general rules presented in this paper can support the design of light wing beam for solar drones.

关键词： Buckling analysis Low-order analytical method Multi-stage optimization Sandwich box beam Solar drones

Comprehensive sizing and optimization method for series-hybrid unmanned convertiplane

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Chinese Journal of Aeronautics 2021年第4期34卷 387-402页

作者： Gang CHEN dongli ma Yuhong JIA Xinglu XIA Cheng HE School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

This paper presents a novel sizing and optimization approach for the emerging serieshybrid unmanned convertiplane,which can be used to translate the top-level design requirements into the design parameters corresponding to the optimal power supply strategy and minimum total takeoff *** method comprehensively considers the design constraints in the rotor,fixedwing,and transition modes,and pays special attention to the characteristic response of Series Hybrid Electric System(S-HES)in complex application scenarios,especially the coupling of battery power,energy,and state-of-charge under high-power discharge conditions,the variation of fuel economy,and the adjustment of power supply *** proposed method,it's possible to rapidly explore the design space in the initial design stage and find out the optimal design results with high confidence.A case study was proposed to verify the *** results reveal the particularity of convertiplane in terms of power requirements,and prove the necessity to consider detailed S-HES characteristic responses during parameter *** optimal design parameters were obtained through the hybrid control parameter optimization,which verified the effectiveness of proposed *** errors and corresponding correction methods were also presented.

关键词： Aircraft optimal design Convertiplane Hybrid electric system Unmanned aerial vehicle Vertical takeoff and landing

Flight strategy optimization for high-altitude long-endurance solar-powered aircraft based on Gauss pseudo-spectral method

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Chinese Journal of Aeronautics 2019年第10期32卷 2286-2298页

作者： Shaoqi WANG dongli ma Muqing YANG Liang ZHANG Guanxiong LI School of Aeronautic Science and Engineering Beihang University

Solar-powered aircraft have attracted great attention owing to their potential for longendurance flight and wide application *** to the particularity of energy system,flight strategy optimization is a significant way to enhance the flight performance for solar-powered *** this study,a flight strategy optimization model for high-altitude long-endurance solar-powered aircraft was *** model consists of three-dimensional kinematic model,aerodynamic model,energy collection model,energy store model and energy loss *** solve the nonlinear optimal control problem with process constraints and terminal constraints,Gauss pseudo-spectral method was employed to discretize the state equations and constraint *** a typical mission flying from given initial point to given final point within a time interval was *** indicate that proper changes of the attitude angle contribute to increasing the energy gained by photovoltaic *** of gravitational potential energy can partly take the role of battery *** these two measures,the optimized flight strategy can improve the final state of charge compared with current constant-altitude constant-velocity *** optimized strategy brings more profits on condition of lower sunlight intensity and shorter daytime.

关键词： Battery pack Flight strategy optimization Gauss pseudo-spectral method Photovoltaic cell Solar-powered aircraft

Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil

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Science China(Technological Sciences) 2017年第10期60卷 1548-1559页

作者： HE Xi WANG JinJun YANG MuQing ma dongli YAN Chao LIU PeiQing Key Laboratory of Fluid Mechanics (Beihang University) Ministry of Education Belting 100191 China Institute of Aircraft Design Heihang University Beijing 100191 China

Two-dimensional steady Reynolds-averaged Navier-Stokes （RANS） equations with transition shear stress transport （SST） model were solved to investigate the effects of Gumey flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 rn/s. The chord length （C） of this airfoil is 5 m and the corresponding Reynolds number is 7.76× 10^5. Gurney flaps with the heights ranging from 0.25%C to 3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack （3°）, Gurney flap with the height of 0.5%C can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gumey flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gumey flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack （≤2°）. However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition.

关键词： gurney flaps lift-enhancement low reynolds number numerical simulation