考虑涂敷的翼型气动高频电磁隐身一体化设计

隐身涂敷设计是先进作战飞机隐身性能的关键技术和必要措施,传统的涂敷设计主要依赖工程经验,缺乏对涂敷设计系统性研究,导致隐身涂敷设计与飞行器气动特性之间关系不明确,难以实现飞行器气动、隐身、重量和使用维护等一体化最优。针对以上问题,本文首先以对称翼型NACA65013为研究对象,对比分析了涂敷厚度和位置对其气动、隐身和重量特性的影响,发现涂敷位置和厚度对翼型气动、隐身特性和重量影响很大,并且三者存在明显的矛盾关系。在此基础上,综合气动、隐身和重量设计要求,选取了最优的涂敷区域,进而开展了考虑涂敷影响的翼型气动隐身优化设计研究,并与不考虑涂敷的翼型外形气动隐身优化设计结果进行对比。结果表明,考虑涂敷的气动隐身设计结果其前向RCS均值比不考虑涂敷的翼型外形气动隐身优化设计结果下降了1个数量级,比初始翼型前向RCS均值下降了90%以上。本文研究工作为飞机气动隐身外形精细化设计和涂敷材料精细化设计提供了高效可靠的设计方法,具有较大的理论和工程价值。

Numerical Tools for the Control of the Unsteady Heating of an Airfoil

This paper concerns the real time control of the boundary layer on an aircraft wing. This new approach consists in heating the surface in an unsteady regime using electrically resistant strips embedded in the wing skin. The control of the boundary layer＇s separation and transition point will provide a reduction in friction drag, and hence a reduction in fuel consumption. This new method consists in applying the required thermal power in the different strips in order to ensure the desired temperatures on the aircraft wing. We also have to determine the optimum size of these strips （length, width and distance between two strips）. This implies finding the best mathematical model corresponding to the physics enabling us to facilitate the calculation for any type of material used for the wings. Secondly, the heating being unsteady, and, as during a flight the flow conditions or the ambient temperatures vary, the thermal power needed changes and must be chosen as fast as possible in order to ensure optimal operating conditions.

Study the Influence of a Gap between the Wing and Slotted Flap over the Aerodynamic Characteristics of Ultra-Light Aircraft Wing Airfoil

The purpose of the study is to assess what the influence of the distance of the gap is between the wing and slotted flap on the aerodynamic characteristics of ultra-light aircraft wing when the flap is retracted. It has been elected numerical approach to the study and it is been realized through applied numerical model of the wing airfoil NACA 2412 for three different lengths of slotted gap size, whose length is expressed as percentages of the airfoil chord. The code ANSYS FLUENT has been applied, as it has been determined RANS （Reynolds-averaged Navier-Stokes） equations and DES （detached-eddy simulation） turbulent model has been used.

Global optimization for ducted coaxial-rotors aircraft based on Kriging model and improved particle swarm optimization algorithm

To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathematical model for calculations. Ducted coaxial-rotors aircraft was taken as an example and Fluent software was applied to the virtual prototype simulations. Through simulation sample points, the total lift of the ducted coaxial-rotors aircraft was obtained. The Kriging model was then constructed, and the function was fitted. Improved particle swarm optimization(PSO) was also utilized for the global optimization of the Kriging model of the ducted coaxial-rotors aircraft for the determination of optimized global coordinates. Finally, the optimized results were simulated by Fluent. The results show that the Kriging model and the improved PSO algorithm significantly improve the lift performance of ducted coaxial-rotors aircraft and computer operational efficiency.

Functional characteristics of dragonfly wings and its bionic investigation progress

Dragonfly is one of the most excellent nature flyers,and its wings exhibit excellent functional characteristics through the coupling and synergy of morphology,configuration,structure and material.The functional characteristics presented by dragonfly wings provide an biological inspiration for the investigation and development of aerospace vehicles and bionics flapping aerocraft flapping-wing micro air vehicles.In resent years,some progresses have been achieved in the researches on the wings' geometric structure,material characteristics,flying mechanism and the controlling mode.In this paper,the functional characteristics of the dragonfly wings including flying,self-cleaning,anti-fatigue,vibration elimination and noise reduction are introduced and the effects of their morphology,configuration,structure and material on the functional characteristics are described.Moreover,the current state of the bionic study on the functional characteristics of dragonfly wings is analyzed and its application prospect is depicted.

Experimental Study of Aerodynamic Behavior in Wind Tunnels with Ornithopter and Plane Models

There are similarities between planes and birds. In fact aerodynamics bases are the same. In order to make some comparisons, this paper presents two series of experiments ： one in a wind tunnel with an omithopter model for measurements of aerodynamic forces with flapping wings. The wing movement has two degrees of freedom flapping around the longitudinal axis of the model and feathering around the wing axis. Measurements of aerodynamic forces： rift and drag in static case averaging values during many cycles of movement and in dynamic case have been performed. The other part of the paper concerns velocity and turbulence measurements on a metal plane wall jet in a wind tunnel with and without a rough surface, with and without acoustic vibrations in order to simulate a plane wing. Aerodynamic characteristics have been obtained in all cases.

Co-simulation and Experimental Study for Wingspan of Flapping Wing Micro Aerial Vehicle

The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.