Abstract:Joined-wing configuration has lower structural weight, higher torsional/flexural strength, smaller induced drag, bigger lift coefficient, and better stability than the normal one. The purpose of this paper is to provide an effective numerical simulation method for calculation and analysis of aerodynamic characteristics of a canard joined-wing UAV. The whole research process of the UAV based on commercial software ANSYS consists of grid modeling, simulations of the flow field of the UAV, qualitative and quantitative analyses of the aerodynamic data. By means of exploring the longitudinal, lateral and directional stability of the UAV, control devices efficiency, we can finally achieve the evaluation of the UAV flight performance. According to preliminary evaluation of the UAV flight performance, we can well complete the design modifications before trial production of the UAV. In addition, the preliminary design optimization of the UAV based on the numerical simulation results will greatly shorten the overall design time, and reduce research costs of the UAV. This present work is helpful for the future aerodynamic analysis of joined-wing UAVs.

Abstract:By taking a large WIG craft as the research object, the numerical simulation of aerodynamic characteristics of the cruise state of WIG craft was calculated based on the finite volume method for solving Navier-Stokes equations. The trend of the lift-drag characteristics of WIG craft with the wing incidence angle and the relative flight height was obtained. The best wing incidence angle was selected as 5.5° by the comprehensive consideration between the lift-drag ratio and drag. The best relative flight height was selected as 0.5 by the comprehensive consideration between the lift-drag ratio and the safety and maneuverability of cruise state. By taking a large WIG craft piggybacking a load aircraft as the research object, the numerical simulation of aerodynamic characteristics of the piggyback cruise state was calculated. The trend of the lift-drag characteristics of the piggyback cruise state with the angle of attack of load aircraft was obtained. The best angle of attack of load aircraft of the piggyback cruise state was selected as 3° by the comprehensive consideration between the economy of the piggyback cruise state and the safety and reliability of the transition from cruise state to separation state.

Abstract:The electromagnetic scattering characteristics of lateral edges of fuselage on aircrafts are studied by numerical simulation to provide some reference for the design of fuselage section. Multilevel fast multipole method (MLFMM) is selected to calculate the Radar Cross Section (RCS) of the edge at different azimuth angles after the geometric model has been built. The magnitude and the width of the peak and the average value of the sidelobe are three important values to be evaluated and they are compared at different polarization methods and frequencies. Sensitivities of the RCS to the geometric parameters - length, angle and thickness of the edge are also studied. The results show that the magnitude of the peak is sensitive to the length and the angle, the width of the peak is sensitive to the frequency, and the average value of the sidelobe is sensitive to frequencies and the angle.

Abstract:For the current deficiencies of internal air to air missile kill probability model against fighter, based on the analysis on the characteristics of aircraft, and methods of Monte Carlo method and kinematics principle are combined to establish kill probability model of warhead fragments and shock wave. Based on the established single kill probability model, objective particle swarm optimization algorithm is used to optimize the loading coefficient, fragments numbers, fragment mass, static scattering angle, static scattering direction angle, the optimization results not only improve the missile kill probability and its main parameters, but also reduce the quality of the warhead.

Abstract:: In order to provide an important technical support for the design of an ground aeroderivative gas turbine with diesel oil.The combustion characteristics and comparative study for an aeroengine with kerosene and diesel oil was studied by using the FLUENT steady pressure solver, P1 radiation model and eddy dissipation breakup (EDU) in cruise condition and the maximum conditions. The flow field, flow distribution,temperature field, total pressure loss, outlet temperature distribution, pollutant and fuel evaporation process of combustor are obtained with aviation kerosene(RP-3)and #0 diesel oil.The results indicate that when the aviation kerosene is changed to #0 diesel oil, the distribution of hot temperature field is consistent and the maximum difference of flow distribution is within 0.45%:the combustion efficiency is reduced by about 4.3% and NO and Soot emissions are equal; the difference of the out temperature distribution and total pressure loss of the outlet are 1% and 4.1% respectively.The calculation results provide the important technical support for the design of an ground aeroderivative gas turbine with diesel oil.

Abstract:Experimental study on a stiffened fuselage panel with circumferential crack subjected to axial tension load was presented. The performance of the crack growth and characteristic of the residual strength for fuselage panel were investigated by damage tolerance experiment. Stress intensity factors (SIF) of experimental structure were analyzed by using ANSYS software. The crack propagation life was evaluated. The residual strength curves were calculated based on the linear elastic fracture mechanics and linear elastic fracture criterion modified by yield correction, respectively. The research indicates analysis results agree well with the crack propagation test data. The relative error is 6.3%, and the calculation accuracy satisfies the requirement of engineering. The estimation results using linear elastic fracture criterion modified by yield correction is more reasonable than using linear elastic fracture mechanics. The relative error is 2.6%.

Abstract:The wide application of composite materials in aerospace engineering makes it critical to evaluate the strength of the composite structures, especially for the simulation of thick laminate joint failure. Based on 3D continuum damage mechanics approach, this paper presents a study for modeling the damage mechanisms in a thick composite joint structure. Also, a user-defined FORTRAN subroutine (UMAT) is written to import the constitutive relation, failure criteria and stiffness degradation model. The substantiation test of the thick laminate joint has also been conducted. The calculation results show that the model could exactly simulate the progressive failure process subjected to tension load, which demonstrates the validity of this intra-laminar damage model for variable parameter iterative calculation and optimization design for thick composite joint structure.

Abstract:A kind of ski-buffer-solution is presented for the parachute recovery according to the requirements of UAVs (unmanned aerial vehicles). The performance of the landing buffer device is mainly achieved by the shock absorber. The key of virtual prototype design is shock absorber modeling. The traditional method is mainly theoretical formula method, which accuracy is difficult to determine. The shock absorber tests are very simple. A dynamical model of the shock absorber is established by using the experimental results of shock absorber static and dropping tests. Based on the dynamical model of shock absorber, a multi-body dynamical model of the full aircraft is established. Then the dynamical characteristics of the UAV landing process are simulated. The simulation results are in good agreement with the experimental results. The dynamical response of the ski structure is analyzed by the nonlinear dynamic simulation with FEM. According to the simulation, the design parameters are optimized finally. The high precision dynamical model established in the paper fully meets the engineering requirements, greatly reduces the test cost, and shortens the development cycle.

Abstract:: In this paper, numerical simulation and experimental technologies are used for the study of atomization and differences of swirl atomizers, which supplying with aviation kerosene and diesel oil. Different geometry parameters are analyzed to investigate their influence on the atomization. And the internal flow field is also revealed through this study. The main contents and conclusions of this study are as follows: there is deviation between numerical simulation and experiments, but the trend of spray cone angle and discharge coefficient varying with pressure presents highly conformity, which verifies that using the fluid volume function (VOF) to track the oil and gas two phase interface is properly for the study. The vortices in the liquid phase and gas phase are the motive for instable flow, which also leading to the waves on the liquid sheet. Geometry parameters make a big difference on the atomization. After optimizing the structure of the nozzle, the flow coefficient and the spray cone angle increased by 0.15 times, and 0.16 times, respectively, and the liquid film thickness decreased by 0.53 times, which obviously improves the atomization quality of the nozzle.

Abstract:In this paper, a new rigid connection element is proposed to accurately distribute the load acting at the specified node to the main structure nodes based on the principle of structure stiffness matrix condensation. For the rigid connection element (RBE3) in the NASTRAN, it requires the user to specify the weight factor of each main structure node subjectively. However, these factors are difficult to determine, which make the calculation of the distributed loads inaccurate. The new element effectively overcomes the shortcomings of the RBE3 element and makes the solution of distributed loads to be more accurate and reasonable. This element also facilitates the user"s modeling process. The numerical results show that the new element can accurately derive the load distribution of the main structure nodes.

Abstract:Combined variation principles can enhance the stability of numerical solution, combined hybrid finite element method of heat transfer equation is built on the basis of the domain decomposition technique. The combined hybrid triangular element, in which the temperature gradient is interpolated by linear polynomials on each element, but the temperature is interpolated by the sum of the linear polynomials and the non-conforming quadratic polynomials, is given. Unlike the combined hybrid rectangular element, only the weighted energy orthogonal relation of the divergence of piecewise linear temperature gradient interpolation and the non-conforming temperature interpolation is given. The stiffness matrix of this element of is equivalent to the conforming triangular linear element, and the non-conforming parts have no contribution to temperature evaluation. At last, the numerical experiments verify the accuracy of the theoretical results.

Abstract:In order to improve the stealth performance of the cockpit glass and optimize the the cockpit’s photoelectric performance parameters, for the Nb-Doped ITO (Indium Tin Oxides) coating of the aircraft cockpit glasses, this paper mainly studied the Nb-Doped ITO coating performance parameters’ influence rule of the technological parameters such as the number of sputtering targets and oxygen flow. The experiment results show that, with the number of targets involved in sputtering increases, the sheet resistance first decreases rapidly, then the falling slope becomes small, and at last tends to constant value; the transmittance changes oscillatorily, and when the sheet resistance is stable, the transmittance gradually becomes smaller; as the oxygen flow increases, the sheet resistance decreases at first, and then increases, when the flow is greater than 6 sccm, the sheet resistance increases rapidly, and the transmittance decreases after oscillation. The sheet resistance and transmittance of the Nb-Doped ITO films with different substrates don’t change great, and the different substrates just affect the degree of vacuum and other process. The technological parameters also have certain effects on the film color.

Abstract:During the high-speed landing for unmanned aerial vehicle (UAV), the deviation caused by cross-wind or initial interference is very dangerous. Based on the characteristics of rudder with high efficiency at high speed, the high speed landing dynamic model of UAV is established, and the rudder deviation control strategy is designed. Further, the non-linear dynamics model of UAV and rudder deviation correction control system are established on MATLAB / Simulink platform to simulate under the situations with initial 1 ° yaw angle or 1m /s continuous vertical crosswind. The simulation results show that the rudder deviation correction control system is able to correct deviation and resist certain cross wind. And, in the correcting process, the maximum lateral deviation is less than 3m and the yaw angle is less than 5 °, which means the system could realize lateral deviation correction.

Abstract:Aircraft R & D is the typical complex system engineering. Multidisciplinary design optimization（MDO） methods are the effective means to improve the aircraft design efficiency and achieve the optimal design scheme. Much research on the aircraft MDO have been done at home and abroad. During the process of aircraft design, the pitching static margin of aircraft must meet the usage requirement, therefore the coupling affections between the major of shape, aerodynamics and weight must be considered. To solve this problem, a practicable solution was proposed. The collaborative MDO process of aircraft shape was created based on Modelcenter. The MDO of an aircraft shape was taken as an example. The optimal shape scheme of this aircraft was obtained. The high effective of MDO methods applied in aircraft design was confirmed. And the difficulties of aircraft MDO were raised.

Abstract:Through studying the failure causes and distribution rules of aviation electronic airborne equipment under the comprehensive environmental stress conditions, we present a new reliability test methods combining the comprehensive test and accelerated reliability growth test. It is based on the reliability test theory of the physical fault ,considering the testing capability and facility test ,combining with the features of airborne equipment design ,using the assessment ideas of ultra-job stress test without changing the eqiupmengt failure machanism .In my paper , to realize diversity factors through reliability simulation model ,I study many kinds of specific technology , such as test method ,project management and application ,ultimately solve the engineering problem that environmental simulation test methods and traditional statistical reliability can not evaluate the airborne equipment under high reliability requirements within short development cycle .The new methods I put forward can make us reasonably set the integrated series of high stress values without changing the failure machanism of the product ,which can effective shorten the time of tese and save the costs.

Abstract:The key technologies of civil aircraft load calibration test was described, including the choice of loads station, starin gauge typical layout, the magnitude of calibration loads, principle of load equations establishment, test report preparation and so on. The corresponding practical comments and proposal was raised. It can be used to proivide some technical guidance for civil aircaft flight load test.

Abstract:According to the characteristics of the helicopter and flight safety requirements, combined with the engineering experience.the paper discusses the basic composition and principle of the flight data recording system, recording parameters selection principle and flight parameter calibration method, lists Some typical fault diagnosis and solution methods in the application of flight t data record system,which provides reference for the design and application of helicopter flight data record system.

Abstract:Civil aircraft is a high-complex and giant product. In order to accurately define this giant product and capture critical construct information of aircraft , product breakdown is needed to form a hierarchical product structure. Different breakdown manners can generate different product structure and capture aircraft construct information from different views.