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29th Congress of the International Council of the Aeronautical sciences, ICAS 2014

作者： Li, Xiaopeng Song, Wenping Han, Zhonghua National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi'an710072 China

ISBN: (纸本)3932182804

In this paper, the interference characteristics and mechanism among the fuselage-stabilizer-control surface which affect the efficiency of the control surface is studied through numerical simulation. The influence of fuselage and stabilizer (including the horizontal distance and vertical distance between the stabilizer and control surface) on the control surface efficiency is exposed and the interference mechanism is revealed. According to the simulation results, some conclusions can be drawn: (1) the existence of the waverider vehicle's fuselage, the existence of stabilizer, and the horizontal and vertical distance between stabilizer and control surface will affect the control surface efficiency;(2) by analyzing the flow interference mechanism, we find that the fuselage's lower Mach number region, the trailing-edge wake, the shock waves and tip vortex wake of the stabilizer, have a negative influence on the control surface. The influence of fuselage's lower Mach number region and the trailing-edge wake are stronger than that of shock waves and tip vortex wake of the stabilizer;(3) through the detailed analysis of the flow patterns, we get the following guidance for the waverider vehicle's layout design: in order to reduce the negative interference on the horizontal control surface efficiency, the horizontal control surface should be mounted in a position away from the stabilizer's trailing-edge wake as far as possible.

关键词： Efficiency

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aerodynamic design OPTIMIZAITON OF HYPERSONIC WING OVER WIDE MACH-NUMBER RANGE CONSIDERING LIFT MATCHING 32

AERODYNAMIC DESIGN OPTIMIZAITON OF HYPERSONIC WING OVER WIDE...

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

作者： Zhang, Yang Han, Zhong-Hua Liu, Fei Xu, Chen-Zhou 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

aerodynamic shape optimization of a hypersonic aircraft over a wide Mach-number range is still challenging, due to the difficulties in cutting down the huge computational cost of high-fidelity CFD simulations and the reasonable compromise between aerodynamic performances at different speed ranges. To address this problem, by applying surrogate-based optimization algorithm, this paper newly proposes a wide-Mach-number-range optimization method considering lift matching, which could improve the usable lift-to-drag ratio (L/D) of the wing when its lift matches the weight of aircraft at different speed ranges. A RANS (Reynolds averaged Navier-Stokes) flow solver is adopted to evaluate objective and constraint functions;Kriging surrogate model combined with a parallel infill-sampling method and a multi-round strategy are employed to find the global optimum. First, aerodynamic performance of the baseline configuration of a hypersonic wing is evaluated and analyzed, and the results show that the wing has a reasonable maximum L/Ds but insufficient usable L/Ds. Then, to increase usable L/Ds of the wing over a wide Mach-number range, planform shape optimization and profile shape optimization are conducted, and significant improvement has been observed. Results show that the hypersonic and supersonic useable L/D of the optimized wing are increased by 10.08% and 29.21% respectively, under the premise that the take-off lift at low speed does not decrease and a better performance over a wide Mach-number range is obtained, which verify the effectiveness of the proposed method. © 2021 32nd Congress of the International Council of the Aeronautical sciences, ICAS 2021. All rights reserved.

关键词： Lift

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IMPROVED WEIGHTED GRADIENT-ENHANCED KRIGING MODEL FOR HIGH-DIMENSIONAL aerodynamic MODELING PROBLEMS 32

IMPROVED WEIGHTED GRADIENT-ENHANCED KRIGING MODEL FOR HIGH-D...

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

作者： Xu, Chen-Zhou Han, Zhong-Hua Zhang, Ke-Shi 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

Weighted gradient-enhanced kriging has been demonstrated to be superior to conventional gradient-enhanced kriging when applied to high-dimensional aerodynamic modeling and optimization problems, through the core idea of summing up a series of submodels with much smaller coloration matrices by appropriate weight coefficients. It avoids the prohibit computational cost associated with directly decomposing the large correlation matrix of a gradient-enhanced kriging, and provides a probable way to ameliorate the "curse of dimensionality". However, with the increase of model training data, the number of required submodels grows rapidly, resulting in another dilemma that the total computation cost of decomposing all the small matrices could become prohibitive. In the paper, an improved formulation of weighted gradient-enhanced kriging is proposed and provides a method to adaptively determine the best suitable number of gradients to be interpolated for each submodel, saving the computation budget for matrix decomposition as much as possible and reaching a win-win situation for both model accuracy and modeling efficiency. Numerical examples are employed to compare the proposed method with other gradient-enhanced modeling approaches. Results demonstrate the advantage of the proposed method in both prediction accuracy and efficiency. It is also applied to the aerodynamic modeling of an RAE2822 airfoil in transonic regime, to further illustrate its capability to support engineering design problems driven by expensive numerical simulations. © 2021 32nd Congress of the International Council of the Aeronautical sciences, ICAS 2021. All rights reserved.

关键词： Kriging

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Infinite swept-wing reynolds-averagednavier-stokes computations with full en transition criterion

Infinite swept-wing reynolds-averagednavier-stokes computati...

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

作者： Kun, Zhang Wenping, Song National Key Laboratory of Science and Technology on Aerodynamic Design Research School of Aeronautics Northwestern Polytechnical University Xi'an China

ISBN: (纸本)9781617820496

A full en transition prediction method is coupled to the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solver to predict the transition point automatically during the simulation of the flow around the infinite swept wings. The three-dimensional linear stability equations are solved using the Cebeci- Stewartson eigenvalue formulation. The locations of the calculated transition points are validated by the experimental results. With the reliable transition information, the accuracy of the infinite swept wing's aerodynamic performance calculated by the RANS solver has been improved. © 2010 by the International Council of Aeronautical sciences - ICAS.

关键词： Swept wings

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Towards efficient high-dimensiona I aerodynamic shape optimization: Surrogate modeling via gradient-enhanced kriging

Towards efficient high-dimensiona I aerodynamic shape optimi...

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2010 Asia-Pacific International Symposium on Aerospace technology, APISAT 2010

作者： Han, Zhonghua Zhang, Keshi National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of Aeronautics Northwestern Polytechnical University Xi'an China

ISBN: (纸本)9787561228999

This paper presents a novel surrogate modeling method that can be potentially used for higher-dimensional aerodynamic shape optimization based on high-fidelity Computational Fluid Dynamics (CFD) methods. The key idea of this method is to use gradient to enhance the prediction of a kriging model. The gradient can be efficiently computed by adjoint method. For give number of samples points, the prediction accuracy of the surrogate model can be improved. In turn, the total computational cost of building a surrogate model at a give accuracy level can be reduced. The presented method is validated by analytical function and demonstrated for building the surrogate model for the object function of an airfoil inverse design problem, with 20 design variables. It is preliminarily shown that gradient-enhanced kriging is promising for high-dimensional aerodynamic problems.

关键词： aerodynamic design Airfoil Gradient-enhanced kriging Kriging model Surrogate model Transonic flow

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aerodynamic design of Megawatt Wind Turbine Blades with NPU-WA Airfoils 4

Aerodynamic Design of Megawatt Wind Turbine Blades with NPU-...

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4th International Conference on Environmental and Energy Engineering, IC3E 2020

作者： Xu, Jianhua Han, Zhonghua Yan, Xiaochao Song, Wenping 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

The NPU-WA airfoils were designed at high design lift coefficient and high Reynolds number, with small sensitivity of the maximum lift coefficient to leading edge roughness and excellent geometric compatibility. Compared to the widely used airfoils, the NPU-WA airfoils have higher lift-to-drag ratio and higher maximum lift coefficient. This paper aims to design a megawatt wind turbine blade in order to demonstrate the advantage of the NPU-WA airfoils. The distributions of chord length and twist angle for a 2 MW wind turbine blade are optimized by a kriging surrogate model-based optimizer, with aerodynamic performance being evaluated by blade element-momentum theory. Results show that compared with the baseline blade, the maximum power coefficient of the optimized NPU blade is larger, and the chord lengths at all span-wise sections are smaller, which is benefit to structural weight reduction. It is shown that the NPU-WA airfoils feature excellent aerodynamic for the design of megawatt wind turbine blades. © Published under licence by IOP Publishing Ltd.

关键词： Airfoils

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The studies of optimum wavelength choice in distributed roughness laminar flow control technique

The studies of optimum wavelength choice in distributed roug...

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

作者： Li, Yueli Li, Dong Yang, Yong National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of Aeronautics Northwestern Polytechnical University Xi'an China

ISBN: (纸本)9781617820496

The key technique of swept wing distributed roughness laminar flow control technique is how to confirm the cross-flow disturbance wavelength used to control transition. The optimum control wavelength of infinite swept wing is studied with the point of physical mechanism of control wave and flow interaction. The method to determine the wavelength is discussed in this paper. By using this method, 8mm is the optimum control wavelength under Saric's experimental condition which consists with Saric's experimental result. By using adaptive search method 1.72mm is obtained as the optimum control wavelength under NWPU model testing condition. By using silk-screen technique roughness array with roughness elements spacing of 1.7mm is added at leadingedge x/c=4%, and transition location is delayed to trailing-edge. © 2010 by the International Council of Aeronautical sciences - ICAS.

关键词： Laminar flow

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An Improved LU-SGS Implicit Scheme for High Reynolds Number Flow Computations on Hybrid Unstructured Mesh

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Chinese Journal of Aeronautics 2012年第1期25卷 33-41页

作者： WANG Gang JIANG Yuewen YE Zhengyin National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical UniversityXi'an 710072China

The lower-upper symmetric Gauss-Seidel （LU-SGS） implicit relaxation has been widely used because it has the merits of less dependency on grid topology, low numerical complexity and modest memory requirements. In original LU-SGS scheme, the implicit system matrix is constructed based on the splitting of convective flux Jacobian according to its spectral radius. Although this treatment has the merit of reducing computational complexity and helps to ensure the diagonally dominant property of the implicit system matrix, it can also cause serious distortions on the implicit system matrix because too many approximations are introduced by this splitting method if the contravariant velocity is small or close to sonic speed. To overcome this shortcoming, an improved LU-SGS scheme with a hybrid construction method for the implicit system matrix is developed in this paper. The hybrid way is that： on the cell faces having small contravariant velocity or transonic contravariant velocity, the accurate derivative of the convective flux term is used to construct more accurate implicit system matrix, while the original Jacobian splitting method is adopted on the other cell faces to reduce computational complexity and ensure the diagonally dominant property of the implicit system matrix. To investigate the convergence performance of the improved LU-SGS scheme, 2D and 3D turbulent flows around the NACA0012 airfoil, RAE2822 airfoil and LANN wing are simulated on hybrid unstructured meshes. The nu- merical results show that the improved LU-SGS scheme is significantly more efficient than the original LU-SGS scheme.

关键词： LU-SGS scheme hybrid unstructured mesh Navier-Stokes equations flux Jacobian convergence performance turbulent flow

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Restarted GMRES + LUSGS implicit method for solution of 3D navier-stokes equations

Restarted GMRES + LUSGS implicit method for solution of 3D n...

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2010 Asia-Pacific International Symposium on Aerospace technology, APISAT 2010

作者： Chen, Lili Song, Bifeng Song, Wenping National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of Aeronautics Northwestern Polytechnical University Xi'an China

ISBN: (纸本)9787561228999

In this paper Generalized Minimum Residual (GMRES) implicit algorithm which has second order property in the convergent speed is presented to solve three-dimensional compressible Reynolds-Averaged steady Navier-stokes equations. The numerical results are compared with the LU-SGS implicit algorithm as well as the Runge-Kutta explicit algorithm on examples of M6 wing as well as LANN wing. The pressure distributions match well with the experimental data, which validate the accuracy of the method used in this paper. Residual versus time steps as well as CPU time convergent more rapidly by using restarted GMRES + LUSGS Implicit Method, which show that computational efficiency can be greatly improved by restarted preconditioning GMRES implicit algorithm.

关键词： GMRES LUSGS Navier-Stokes equations Precondition method

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Study of aerodynamic and inertial forces of a experimental and numerical methods

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Chinese Journal of Aeronautics 2022年第6期35卷 63-76页

作者： Xiaowu YANG Bifeng SONG Wenqing YANG Dong XUE Yang PEI Xinyu LANG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical UniversityXi’an 710072China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and *** obtain the real deformation pattern of the flapping wing,the digital image correlation technology was used to measure the dynamic deformation of the *** dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic *** dynamic deformation data were further used to calculate the inertial forces by regarding the wing as a system of particles to take into account the wing *** temporal variation of the forces produced by the flapping wing was measured by a miniature load *** numerical results provide more flow details of the unsteady aerodynamics of the flapping wing in terms of vortex formation and *** calculated results of the inertial forces are analyzed and compared with the CFD results which represent the aerodynamic *** addition,the total forces,i.e.,the sum of the CFD result and inertial result,are compared with the experimental results,and an overall good agreement is obtained.

关键词： aerodynamic force CFD Digital image correlation Flapping-wing micro air vehicles Inertial force

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