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AIAA Atmospheric Flight Mechanics Conference 2011

作者： Xu, He-Yong Ye, Zheng-Yin National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an 710072 China

ISBN: (纸本)9781624101533

In the present paper, a new kind of flutter exciter for the aircraft flight testing is numerically simulated, and its aerodynamic characteristics are investigated, using the CFD technology of solving unsteady Euler equations based on unstructured overset grids. The numerical results show that the flutter exciter system can generate a reasonably stable exciting force, which is very convenient for the aircraft flutter testing. Additionally, the flutter efficiency can be influenced by some parameters, such as slotted central angle β, diameter of the slotted cylinder d, distance ΔL between the rotational axis and the trailing edge of the vane, section shape of the slotted cylinder, and so on. Too large β, ΔL or too small β, ΔL have bad effect on the flutter efficiency;a larger force can be generated with a larger diameter d;the crescent shape is a better choice. The type of near-root half-opening can generate a little larger exciting force for the flutter testing, comparing with the type of near-tip half-opening. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Efficiency

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Shock detection and limiting with discontinuous galerkin methods for euler equations on unstructured mesh

Shock detection and limiting with discontinuous galerkin met...

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27th Congress of the International Council of the Aeronautical sciences 2010, ICAS 2010

作者： Haibing, Hao Yong, Yang National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an 710072 China

ISBN: (纸本)9781617820496

The purpose of this paper is to simulate the transonic steady-state flows with the discontinuous Galerkin finite element method which is very sensitive to the spurious oscillations. In this article, a strategy for combining the discontinuous detector and limiter is employed to suppress the spurious oscillations near such discontinuities. The discontinuous detector is based on physicical characters of shock waves which can effectively distinguish a smooth extremum and a shock wave;Limiter is followed by Barth and Jespersen's monotonic limiter which is only used to modify the solutions slope of the detected regions to ensure the solution being monotonic. Numerical simulation for both 2D and 3D Euler Equations are presented to demonstrate the accuracy of the developed discontinuous Galerkin method. The results show that the detector can effectively identify the discontinuous regions and the limiter can effectively suppress the spurious numerical oscillations. Moreover, DG method has less numerical dissipation and excellent ability to capture shocks compared with the finite volume method with the same accuracy order. © 2010 by the International Council of Aeronautical sciences - ICAS.

关键词： Euler equations

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research on aerodynamic flow acceleration induced by one atmosphere uniform DBD plasma based on PIV

Research on aerodynamic flow acceleration induced by one atm...

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2013 International Conference on Intelligent Materials and Measurement, ICIMM 2013

作者： Li, Feng Gao, Chao Zheng, Bo Rui Wang, Yu Shuai National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an 710072 China

ISBN: (纸本)9783037858448

The aerodynamic flow acceleration with one atmosphere uniform induced by dielectric-barrier-discharge plasma actuation were studied based on PIV. The flow fields induced by the dielectric barrier discharge with different discharge models and actuation parameters were investigated. In term of the obtained velocity distributions, a comparative study on the effect of excitation voltages, carrier frequencies, pulse frequencies and duty ratios on plasma actuation was presented and the optimum actuation parameters was provided. The results of this study indicate: 1) The induced velocity increases linearly with excitation voltage and frequency. 2) When fpp>300Hz, it shows an opposite tendency. © (2013) Trans Tech Publications, Switzerland.

关键词： aerodynamics

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Comparison of infill sampling criteria in kriging-based aerodynamic optimization

Comparison of infill sampling criteria in kriging-based aero...

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28th Congress of the International Council of the Aeronautical sciences 2012, ICAS 2012

作者： Liu, Jun Han, Zhonghua Song, Wenping National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an 710072 China

ISBN: (纸本)9781622767540

Kriging-based optimization methods are of great interest for aerodynamic design optimization where high-fidelity thus timeconsuming computational fluid dynamics (CFD) are used. In the framework of kriging-based optimization, a core technique called sampling infill criteria (also called adaptive sampling) is used both to search the design space and to refine the surrogate models. Among all the infill criteria, expected improvement (EI) is the favorite one while others are also still in use. However, there is little research compared these criteria when kriging-based optimization method is applied in the aerodynamic design optimization. The following paper addresses this issue by investigating 6 types of infill criteria in the drag minimization problem of the RAE2822 airfoil with different number of design variables. For each infill criterion and each number of design variables, the optimization process is repeated 30 times, and the averaged value and standard deviation are compared. The results show that, some criteria can be comparable to EI or even slight better than EI, while some criteria are much worse.

关键词： Kriging

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A comparison study on transition characteristics of NLF forward-swept-wing and aft-swept-wing 31

A comparison study on transition characteristics of NLF forw...

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31st Congress of the International Council of the Aeronautical sciences, ICAS 2018

作者： Zhu, Zhen Song, Wen-Ping Han, Zhong-Hua Xu, Jian-Hua National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an710072 China

ISBN: (纸本)9783932182884

The forward-swept-wing (FSW) is a favorable concept in natural laminar flow (NLF) wing design. It has smaller leading edge swept angle λLE than that of aft-swept-wing (ASW), which may avoid leading edge transition induced by cross flow (CF) instability. However, there are still some key technological issues, such as the characteristics of boundary layer transition in transonic flow, aerodynamic performances and the differences of CF instability between FSW and ASW, are not clear. A comparison study on transition characteristics, boundary layer stability and aerodynamic performances of NLF FSW and ASW is carried out. A three-dimensional Reynolds-averaged Navier-Stokes (RANS) solver coupled with a dual eN transition prediction method based on linear stability theory (LST) is used. Fixed wave angle method and fixed wave number method are employed for Tollmien-Schlichting (TS) instability and cross-flow instability, respectively. The results show that, 1). With the same λLE, the FSW in this paper has a smaller CF instability and larger area of laminar flow than that of ASW. 2). Compared with ASW, the FSW has larger swept angle at about 50%-60% chord where shock wave may occur, which leads to much weaker shock wave. 3). CL/CD of the FSW is 13.7% larger than that of ASW. It can be concluded that FSW has more advantages in NLF supercritical wing design. © 31st Congress of the International Council of the Aeronautical sciences, ICAS 2018. All rights reserved.

关键词： Swept wings

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Efficient aerodynamic optimization using hierarchical kriging combined with gradient 30

Efficient aerodynamic optimization using hierarchical krigin...

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30th Congress of the International Council of the Aeronautical sciences, ICAS 2016

作者： Song, Chao Yang, Xudong Song, Wenping National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an710072 China

ISBN: (纸本)9783932182853

The gradient information could improve the design efficiency of the original kriging model. A new method combined gradients with Hierarchical Kriging (HK) model is developed in this paper. The model is built in two steps. At first, initial sample points and the gradient with respect to design variables are computed by high-fidelity solvers. Gradient information and a selected step size are used for Taylor approximation to obtain derived sample points. Then these sample point are used for building a low-fidelity kriging model. At last, a high-fidelity model can be obtained by adjusting the low-fidelity using the initial samples. An analytical function test case demonstrates that the gradient enhanced Hierarchical Kriging (GEHK) model has overcome limitations of traditional gradient-based kriging model, and the prediction accuracy of the model can be improved evidently. In the airfoil drag reduction case, the GEHK model improves the optimization efficiency, and could get a better result compared with the ordinary kriging model.

关键词： Kriging

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Study of the boundary layer on a plate aerodynamically induced by multiple DBD plasma based on PIV

Study of the boundary layer on a plate aerodynamically induc...

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4th International Conference on Information technology for Manufacturing Systems, ITMS 2013

作者： Li, Feng Gao, Chao Zheng, Bo Rui Wang, Yu Shuai National Key Laboratory of Science and Technology Aerodynamic Design and Research Northwestern Polytechnical University Xi'an 710072 China

ISBN: (纸本)9783037858783

The boundary layer aerodynamic flow acceleration with one atmosphere uniform induced by multiple dielectric-barrier-discharge plasma actuation were studied based on PIV. Through double actuators alternating discharge, the multiple dielectric barrier discharge mode have been proposed and tested. The efficiencies of the plasma actuators in Pulsed-pulsed, Steady-steady, Pulsed-steady and Steady-pulsed discharge modes were explored. Based on the above results, the boundary layer flow acceleration performance of multiple plasma actuators has been discussed and the more efficient discharge pattern has been proposed. The results of this study indicate that the airflow acceleration effect of multiple plasma actuators mainly occurs in paraelectric direction and the pulsed-pulsed is the more efficient multiple plasma actuation mode. © (2013) Trans Tech Publications, Switzerland.

关键词： Boundary layers

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Experiments of cross-flow instability in a swept-wing boundary layer

Experiments of cross-flow instability in a swept-wing bounda...

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27th Congress of the International Council of the Aeronautical sciences 2010, ICAS 2010

作者： Sui-han, Zuo Yong, Yang Dong, Li National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an 710072 China

ISBN: (纸本)9781617820496

Stationary cross-flow instabilities and transition pattern in the boundary layer of a 45-degree swept wing with and without 3D artificial leading edge roughness were investigated by sublimation method in two wind tunnels of Northwestern Polytechnical University. For the experiments in Low Turbulence Wind Tunnel, straight transition lines behind the minimum pressure point which are dominated by T-S instabilities appeared on the model without artificial roughness in the Reynolds number range of 5.50×105~1.65×106. The traces of the most amplified stationary cross-flow waves were detected when Re=1.38×106, and the spacing of stripes is consistent with the results of linear stability theory. The extreme sensitivity of the stationary disturbance to leading edge roughness is verified at Re=1.65×106. With different spacing leading edge roughness applied, the most amplified waves were suppressed by the 2.5mm spacing roughness, and harmonics with half of the input wavelengths appeared when 6.0-8.0mm spacing roughness were printed. In NF-3 wind tunnel, the experiments found that as turbulence level increase, the amplification of stationary crossflow waves are suppressed. Jagged transition line dominated by stationary cross-flow waves appeared in the upstream region of the minimum pressure point at Re=2.20×106, and the transition was delayed successfully when 1.7mm leading edge roughness was printed.

关键词： Wind tunnels

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SFedXL: Semi-Synchronous Federated Learning With Cross-Sharpness and Layer-Freezing

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IEEE Internet of Things Journal 2025年

作者： Zhao, Mingxiong Zhao, Shihao Feng, Chenyuan Yang, Howard H. Niyato, Dusit Quek, Tony Q. S. Yunnan University National Pilot School of Software Kunming650500 China Ministry of Education Engineering Research Center of Integration and Application of Digital Learning Technology Beijing100039 China Ministry of Education Engineering Research Center of Cyberspace Kunming650504 China Yunnan University of Finance and Economics Yunnan Key Laboratory of Service Computing Kunming650221 China EURECOM Sophia Antipolis06410 France Zhejiang University University of Illinois Urbana-Champaign Institute Zhejiang University Haining314400 China Nanyang Technological University School of Computer Science and Engineering 639798 Singapore Singapore University of Technology and Design Information Systems Technology and Design Pillar 487372 Singapore

Federated learning (FL) emerges as a potential solution for enabling multiple terminal devices to collaboratively accomplish computational tasks within an Unmanned Aerial Vehicle (UAV) swarm. However, traditional FL approaches, predicated on synchronous data aggregation, are not feasible for a UAV swarm owing to the inherently variable and dynamic nature of their communication networks compared with terrestrial systems. Furthermore, the data procured by UAVs is often highly heterogeneous, attributable to disparities in deployment environments and device attributes. Considering the distinct flight paths and unique operational conditions encountered by different UAVs, a considerable amount of data remains unlabeled. To tackle the challenges associated with asynchronous operations and the prevalence of unlabeled data, we introduce a novel framework termed Semi-synchronous FL with Cross-Sharpness and Layer-Freezing (SFedXL), tailored for a UAV swarm. In particular, we devise a cross-sharpness model training strategy aimed at optimizing the utilization of both labeled and unlabeled datasets. Additionally, we propose an innovative semi-synchronous model aggregation protocol, complemented by client-specific layer-freezing and client cluster scheduling, designed to expedite the training process. Our simulation results indicate that the proposed algorithm surpasses current FL methods in terms of object recognition accuracy and communication efficiency, albeit with a trade-off of increased local computation latency. © 2014 IEEE.

关键词： Federated learning

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Natural-Laminar-Flow Airfoil design Optimization Considering Crossflow Instability When Configured on a Swept Wing 32

Natural-Laminar-Flow Airfoil Design Optimization Considering...

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32nd Congress of the International Council of the Aeronautical sciences, ICAS 2021

作者： Xu, Zhen-Ming Han, Zhong-Hua Song, Wen-Ping Institute of Aerodynamic and Multidisciplinary Design Optimization National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of Aeronautics Northwestern Polytechnical University Xi'an710072 China

ISBN: (纸本)9783932182914

This paper proposes a novel design optimization method for transonic natural-laminar-flow (NLF) airfoils allowing for suppressing crossflow instability (CFI) when configured on a three-dimensional (3-D) swept wing. The distribution of the nondimensionalized crossflow pressure gradient (CFPG), a newly proposed flow parameter by the authors, is used as the objective flow characteristics related to crossflow in the corresponding 3-D case and combined with the total drag as the weighted objective function. The flow field and transition location are obtained by an extensively verified Reynolds averaged Navier-Stokes equations flow solver coupled an eN method based on the linear stability theory. A surrogate-based optimization framework with Kriging model and parallel infill-sampling method is used to solve the optimization problem. The proposed method is demonstrated by the design optimization of a transonic NLF airfoil named NPU-LSC-72613, which is assumed to be configured on an infinite wing with a 30 deg sweep angle. Damped CFI and extensive laminar flow are obtained on the wing's upper surface, which demonstrates the feasibility of using the nondimensionalized CFPG to enable a 2-D NLF airfoil design optimization considering 3-D effects of crossflow. © 2021 32nd Congress of the International Council of the Aeronautical sciences, ICAS 2021. All rights reserved.

关键词： Laminar flow

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