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Song L.,Beihang University | Yang H.,Beihang University | Zhang Y.,AVIC First Aircraft Institute | Zhang H.,Beihang University | Huang J.,Beihang University
Chinese Journal of Aeronautics | Year: 2014

The influence of dihedral layout on lateral-directional dynamic stability of the tailless flying wing aircraft is discussed in this paper. A tailless flying wing aircraft with a large aspect ratio is selected as the object of study, and the dihedral angle along the spanwise sections is divided into three segments. The influence of dihedral layouts is studied. Based on the stability derivatives calculated by the vortex lattice method code, the linearized small-disturbance equations of the lateral modes are used to determine the mode dynamic characteristics. By comparing 7056 configurations with different dihedral angle layouts, two groups of stability optimized dihedral layout concepts are created. Flight quality close to Level 2 requirements is achieved in these optimized concepts without any electric stability augmentation system. © 2014 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.

Zhang X.,Cranfield University | Bianchi F.,Cranfield University | Liu H.,AVIC First Aircraft Institute
Aeronautical Journal | Year: 2012

A numerical model is developed for predicting low-velocity impact damage in laminated composites. Stacked shell elements are employed to model laminate plies with discrete interface elements in pre-determined zones to model the onset and propagation of matrix cracks and delamination. These interface elements are governed by a bi-linear cohesive failure law. Cohesive element zone size is determined by a separate finite element analysis using solid elements to identify the stress concentration sites. In order to save the computational effort, low-velocity impact load is modelled by quasi-static loading. Influence of contact force induced friction on shear driven mode II delamination is modelled by a friction model. For a clustered cross-ply laminate, calculated impact force and damage area are in good agreement with the test results. It is shown that matrix cracks should be included in the model in order to simulate delamination in adjacent interface. The practical outcome of this research is a validated modelling approach that can be further improved for predicting low-velocity impact damage in other stacking sequences.

Chen L.,AVIC First Aircraft Institute | Song B.,Northwestern Polytechnical University | Song W.,Northwestern Polytechnical University | Yang W.,Northwestern Polytechnical University
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2015

Due to the small size and light weight, flexible deformation plays an important part in flapping wing aerodynamics. the aero-elastic performances of Flapping-wing Micro Air Vehicle (FMAV) are researched by solving the Reynolds-Averaged Navier-Stokes (RANS) equations and structural dynamic equations. An aerodynamic-structural coupling computational framework is developed, which is able to simulate aerodynamic-structural coupling characteristics of flexible flapping wings. The flapping wing's unsteady aerodynamic characteristics is obtained by solving Reynolds Average Navier-Stokes (RANS) equations. Structural dynamic equations capable of describing the flapping wing's movement are derived by using Hamilton principle, then discreted through finite element method and solved by Newmark solution to get structural characteristics. Loose coupling method is used. On the basis of the above work, CFD/CSD (Computational Fluid Dynamics/Computational Structural Dynamics) grid data exchange method, dynamic grid technology as well as coupling method are further investigated, and finally a complete set of CFD/CSD coupling solver is developed. Computational results show good agreement with experimental results, which prove that the method developed in this paper are valid and suit for simulation of flexible flapping wing. Effect of inertia loads and kinetic parameters are also investigated, which can help to understand the mechanisms of flexible flapping wing's aeroelasticity and give a guidance in the design of flexible flapping wing. ©, 2015, Editorial Board of ACTA AERODYNAMICA SINICA. All right reserved.

Chen G.,Northwestern Polytechnical University | Wang T.,Northwestern Polytechnical University | Liu M.,AVIC First Aircraft Institute | Sun H.,Northwestern Polytechnical University | Zhang Y.,Northwestern Polytechnical University
Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University | Year: 2012

Sections 1 through 4 of the full paper explain our exploration which we believe can lead to obtaining lubrication design and heat transfer analysis that are more accurate and effective than previous ones. Their core consists of: "The lubrication design and the heat transfer analysis in the bearing chamber of an aero-engine depend on our understanding of its lubricant two-phase flow characteristics. Researching on the oil/air two-phase flow based on flow pattern is an effective approach to obtaining the flow characteristics. According to the need of determining the oil/air two-phase flow form by experiments, considering the identification ability and experiment accessibility, the flow pattern characteristic parameters are proposed with numerical analysis and experimental results, and their robustness about the identification ability in broader operating conditions are discussed: the flow pattern characteristic parameters refer to volume oil content and dimensionless velocity, which are used to identify the homogeneous flow and oil/air(oil drops) stratified flow(the two primary oil/air two-phase flow in bearing chamber). " The results of our exploration, presented in Figs.2,3 and 4, and their analysis show preliminarily that our exploration is indeed a significant work for realizing accurate and efficient lubrication design and heat transfer analysis.

Xu G.,AVIC First Aircraft Institute | Lie L.,AVIC First Aircraft Institute
55th Israel Annual Conference on Aerospace Sciences 2015 | Year: 2015

An ANFIS (Adaptive Neuro-Fuzzy Inference System) based on Sugeno-type fuzzy inference is developed for modern flight control system. It can replace the traditional gain scheduling according to the altitude or Mach number which is only one-parameter adjusting. The ANFIS trained by the designed data can realize double parameters gain regulating. The simulation results verify that the ANFIS can generate the same gains on the designed flight conditions. It can get a good control effect on other untrained flight conditions, even if the system has huge modeling error. Copyright © (2015) by Technion Israel Institute of Technology. All rights reserved.

Luo W.,AVIC First Aircraft Institute | Tan S.,AVIC First Aircraft Institute | Xie H.,AVIC First Aircraft Institute | Huo Y.,AVIC First Aircraft Institute
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2013

Aircraft flutter test model design and actual testing are often delayed because of inaccurate model design parameters, and there are few research publications in this field. This paper studied the basic design scales and other factors such as overweight ratio, section shape, equivalent mass ratio, etc., for flutter test model design. Meanwhile, it discussed the equivalent mass ratio and the section dimensional ratio of the aircraft basic spar frame model. They are convenient concepts to evaluate the basic design scales and other factors for designing flutter test models. As an example, reasonable design scales and factors are provided by the proposed method for an aircraft component flutter model design, which thus succeeds in solving potential problems in the primary stage and shortens the design and manufacture period of the test model from 6 to 3 months.

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