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Wang Y.-Y.,Northwestern Polytechnical University | Zhang B.-Q.,Northwestern Polytechnical University | Chen Y.-C.,Northwestern Polytechnical University | Chen Y.-C.,Shanghai Aircraft Design Institute
Applied Mathematics and Mechanics (English Edition) | Year: 2011

A robust airfoil optimization platform is constructed based on the modified particle swarm optimization method (i.e., the second-order oscillating particle swarm method), which consists of an efficient optimization algorithm, a precise aerodynamic analysis program, a high accuracy surrogate model, and a classical airfoil parametric method. There are two improvements for the modified particle swarm method compared with the standard particle swarm method. First, the particle velocity is represented by the combination of the particle position and the variation of position, which makes the particle swarm algorithm a second-order precision method with respect to the particle position. Second, for the sake of adding diversity to the swarm and enlarging the parameter searching domain to improve the global convergence performance of the algorithm, an oscillating term is introduced to the update formula of the particle velocity. At last, taking two airfoils as examples, the aerodynamic shapes are optimized on this optimization platform. It is shown from the optimization results that the aerodynamic characteristic of the airfoils is greatly improved in a broad design range. © 2011 Shanghai University and Springer-Verlag Berlin Heidelberg. Source

Li Y.,Northwestern Polytechnical University | Bai J.,Northwestern Polytechnical University | Guo B.,Shanghai Aircraft Design Institute | Yang T.,Northwestern Polytechnical University | He X.,Northwestern Polytechnical University
Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University | Year: 2015

First we explore the influence on the aerodynamic characteristics of the tilt angle, height and angle of the installation of the blended winglet. Then, we build the optimization system with FFD technology, Latin hypercube sampling method, Kriging surrogate model and the improved particle swarm optimization algorithm. We apply this system to the blended winglet; through the appropriate arrangement of the FFD control body frame we achieve a framework for FFD parameterized design of multiple control winglets. Optimization results show that the drag of the designed blended winglets decrease obviously as compared with that of the original configuration. Compared with the parameter analysis of those three wingtip devices ("wingtip extension", "eddy diffusion" and "double fork scimitar"), we draw some valuable conclusions for the design of wingtip devices. Source

Han Z.-R.,Nanjing University of Aeronautics and Astronautics | Lu Z.-L.,Nanjing University of Aeronautics and Astronautics | Guo T.-Q.,Nanjing University of Aeronautics and Astronautics | Chen Y.-C.,Nanjing University of Aeronautics and Astronautics | Chen Y.-C.,Shanghai Aircraft Design Institute
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2012

Based on the compressible viscous flow, disorder degree of the flow velocity is proposed to be the indicator variable for a grid adaption. Jameson cell-centred scheme of Finite Volume Method and five-stage Runge-Kutta approach/dual time-stepping approach are used to solve steady/unsteady N-S equations. Spalart-Allmaras One-Equation is employed to the simulations of turbulent flows. In order to improve the capability of catching flow separation characteristics, the grid adaption method is used during the numerical simulation of the two-dimensional static stall and dynamic stall. The example results indicate that the grid adaption method can obviously improve the calculation accuracy in the case of increasing a small amount of grid cells. Source

Xiao K.,Shanghai Aircraft Design Institute
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2012

High temperature compression tests at a temperature range of 200-500°C with various strain rates 0.001-1 s -1 on a conventional as-cast AZ31 were carried out using a Gleeble-1500 dynamic material testing machine. The effects of deformation temperature and strain rate on microstructure evolution of the as-cast AZ31 magnesium alloy were analyzed by introducing temperature-compensated strain rate (Zener-Hollomon parameter, Z value). The results of the microstructure observations indicate that as the volume fraction of DRX grains increased, the size of DRX grain size is decreased. The mean size of the DRX grains decreases and the volume fraction of DRX grains increase with an increase of Z value. The three dimensional graph has been established to provide a clear guideline for forming craft selection. Source

Bai J.-Q.,Northwestern Polytechnical University | Qiu Y.-S.,Northwestern Polytechnical University | Chen Y.-C.,Shanghai Aircraft Design Institute | Li Y.-L.,Shanghai Aircraft Design Institute | Zhou T.,Shanghai Aircraft Design Institute
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2012

By numerical simulation, the influence of slat tracks and flap track fairings on aerodynamic performance of high-lift system and its flow mechanism have been investigated. The results indicate that these brackets just bring a little descent to the linear part of lift curve, but cause a remarkable loss to the angle of stall and maximum lift coefficient. The mechanism lies in that low-momentum strong wake flow generated by slat tracks mixed with the boundary layer of main wing, which causes the remarkable loss of the lift. At high angle of attack, slat tracks will generate large area flow separation. The flap slot section area diminishes for blockage effect of flap track fairings. This made the high speed flow of flap slot faster, and made for blowing the separation flow on flap surface away. Source

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