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A novel high-order scheme for numerical simulation of wake flow over helicopter rotors in hover

Chinese Journal of Aeronautics 2022年第5期35卷 260-274页

作者： Shaoqiang HAN Wenping SONG Zhonghua HAN Institute of aerodynamic and Multidisciplinary design Optimization National Key Laboratory of Science and Technology on Aerodynamic Design and ResearchSchool of AeronauticsNorthwestern Polytechnical UniversityXi’an 710072China

Accurate prediction of tip vortices is crucial for predicting the hovering performance of a helicopter rotor.A new high-order scheme(we call it WENO-K)proposed by our research group is employed to minimize numerical dissipation and extended to numerical simulation of unsteady compressible viscous flows dominated by tip vortices over hovering rotors.WENO-K is referred to as an adaptively optimized WENO scheme with Gauss-Kriging reconstruction,and its advantage is to reduce dissipation in smooth regions of flow while preserving high-resolution around discontinuities.Here WENO-K scheme is adopted to reconstruct left and right state values within the Roe Riemann solver updating the inviscid fluxes on a structured dynamic overset grid.To minimize the accuracy loss for high-order reconstruction on artificial boundaries of overset grid,a method of multilayer fringes is proposed to carry out interpolation between background grid and blade grid.Massively parallel computing considering automatic load balance on averagely partitioned overset grid is developed to reduce the wall-clock time of an unsteady simulation.Numerical results for Caradonna-Tung(C-T)rotor in hover at the conditions of subsonic and transonic tip Mach numbers show that the thrust coefficient error for the result of WENO-K scheme is no more than 3%.Compared with WENO-JS scheme,WENO-K scheme achieves about 40%improvement on accuracy of predicting rotor thrust with only 4.1%extra computational cost.More importantly,WENO-K scheme can capture more sophisticated unsteady flow structures and resolve tip vortices to a larger wake age with an increment of about 270°compared to WENO-JS scheme.

关键词： Dynamic overset grid Helicopter rotors High-order scheme Unsteady flow Vortex flow WENO scheme

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Effect of anisotropic resistance characteristic on boundary-layer transitional flow

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Applied Mathematics and Mechanics(English Edition) 2022年第12期43卷 1935-1950页

作者： Zheng HONG Zhengyin YE Kangling WU Kun YE national key laboratory of Science and Technology on aerodynamic design and research Northwestern Polytechnical UniversityXi'an 710072China

It is observed that the feather surface exhibits anisotropic resistances for the streamwise and spanwise flows.To obtain a qualitative understanding about the effect of this anisotropic resistance feature of surface on the boundary-layer transitional flow over a flat plate,a simple phenomenological model for the anisotropic resistance is established in this paper.By means of the large eddy simulation(LES)with high-order accurate finite difference method,the numerical investigations are conducted.The numerical results show that with the spanwise resistance hindering the formation of vortexes,the transition from laminar flow to turbulent flow can be delayed,and turbulence is weakened when the flow becomes fully turbulent,which leads to significant drag reduction for the plate.On the contrary,the streamwise resistance renders the flow less stable,which leads to the earlier transition and enhances turbulence in the turbulent region,causing a drag increase for the plate.Thus,it is indicated that a surface with large resistance for spanwise flow and small resistance for streamwise flow can achieve significant drag reduction.The present results highlight the anisotropic resistance characteristic near the feather surface for drag reduction,and shed a light on the study of bird’s efficient flight.

关键词： anisotropic resistance transitional flow drag reduction numerical simulation

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Multi-infill strategy for kriging models used in variable fidelity optimization

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Chinese Journal of Aeronautics 2018年第3期31卷 448-456页

作者： Chao SONG Xudong YANG Wenping SONG national key laboratory of Science and Technology on aerodynamic design and research Northwestern Polytechnical University

In this paper, a computationally efficient optimization method for aerodynamic design has been developed. The low-fidelity model and the multi-infill strategy are utilized in this approach.Low-fidelity data is employed to provide a good global trend for model prediction, and multiple sample points chosen by different infill criteria in each updating cycle are used to enhance the exploitation and exploration ability of the optimization approach. Take the advantages of lowfidelity model and the multi-infill strategy, and no initial sample for the high-fidelity model is needed. This approach is applied to an airfoil design case and a high-dimensional wing design case.It saves a large number of high-fidelity function evaluations for initial model construction. What＇s more, faster reduction of an aerodynamic function is achieved, when compared to ordinary kriging using the multi-infill strategy and variable-fidelity model using single infill criterion. The results indicate that the developed approach has a promising application to efficient aerodynamic design when high-fidelity analyses are involved.

关键词： aerodynamics Infill criteria Kriging models Multi-infill Optimization

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Robust design of NLF airfoils

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Chinese Journal of Aeronautics 2013年第2期26卷 309-318页

作者： Li Jing Gao Zhenghong Huang Jiangtao Zhao Ke National Key Laboratory of Aerodynamic Design and Research Northwestern Polytechnical University

A robust optimization design approach of natural laminar airfoils is developed in this paper. First, the non-uniform rational B-splines （NURBS） free form deformation method based on NURBS basis function is introduced to the airfoil parameterization. Second, aerodynamic characteristics are evaluated by solving Navier-Stokes equations, and theγ-Reθt transition model coupling with shear-stress transport （SST） turbulent model is introduced to simulate boundary layer transition. A numerical simulation of transition flow around NLF0416 airfoil is conducted to test the code. The comparison between numerical simulation results and wind tunnel test data approves the validity and applicability of the present transition model. Third, the optimization system is set up, which uses the separated particle swarm optimization （SPSO） as search algorithm and combines the Kriging models as surrogate model during optimization. The system is applied to carry out robust design about the uncertainty of lift coefficient and Mach number for NASA NLF-0115 airfoil. The data of optimized airfoil aerodynamic characteristics indicates that the optimized airfoil can maintain laminar flow stably in an uncertain range and has a wider range of low drag.

关键词： Free form deformation Transition model NLF airfoils Particle swarm optimization （PSO） Robust design Surrogate model

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aerodynamic design optimization of nacelle/pylon position on an aircraft

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Chinese Journal of Aeronautics 2013年第4期26卷 850-857页

作者： Li Jing Gao Zhenghong Huang Jiangtao Zhao Ke National Key Laboratory of Aerodynamic Design and Research Northwestern Polytechnical University

The arbitrary space-shape free form deformation （FFD） method developed in this paper is based on non-uniform rational B-splines （NURBS） basis function and used for the integral parameterization of nacelle-pylon geometry. The multi-block structured grid deformation technique is established by Delaunay graph mapping method. The optimization objects of aerodynamic characteristics are evaluated by solving NavierStokes equations on the basis of multi-block structured grid. The advanced particle swarm optimization （PSO） is utilized as search algorithm, which com-bines the Kriging model as surrogate model during optimization. The optimization system is used for optimizing the nacelle location of DLR-F6 wing-body-pylon-nacelle. The results indicate that the aerodynamic interference between the parts is significantly reduced. The optimization design system established in this paper has extensive applications and engineering value.

关键词： Delaunay graph mapping Free form deformation （FFD） Kriging model Navier-Stokes equations Particle swarm optimization （PSO） Space-shape

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research on multi-fidelity aerodynamic optimization methods

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Chinese Journal of Aeronautics 2013年第2期26卷 279-286页

作者： Huang Likeng Gao Zhenghong Zhang Dehu National Key Laboratory of Aerodynamic Design and Research Northwestern Polytechnical University

Constructing high approximation accuracy surrogate model with lower computational cost has great engineering significance. In this paper, using co-Kriging method, an efficient multi-fidelity surrogate model is constructed based on two independent high and low fidelity samples. Co-Kriging method can use a greater quantity of low-fidelity information to enhance the accuracy of a surrogate of the high-fidelity model by modeling the correlation between high and low fidelity model, thus computational cost of building surrogate model can be greatly reduced. A wing-body problem is taken as an example to compare characteristics of co-Kriging multi-fidelity （CKMF） model with traditional Kriging based multi-fidelity （KMF） model. A sampling convergence of the CKMF model and the KMF model is conducted, and an appropriate sampling design is selected through the sampling convergence analysis. The results indicate that CKMF model has higher approximation accuracy with the same high-fidelity samples, and converges at less high-fidelity samples. A wing-body drag reduction optimization design using genetic algorithm is implemented. Satisfying design results are obtained, which validate the feasibility of CKMF model in engineering design.

关键词： aerodynamics Co-Kriging Multi-fidelity Optimization Surrogate model

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Simulation of Flow Around Cylinder Actuated by DBD Plasma

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Plasma Science and Technology 2016年第7期18卷 768-774页

作者：王玉玲高超武斌胡旭 national key laboratory of Science and Technology on aerodynamic design and research Northwestern Polytechnical University

The electric-static body force model is obtained by solving Maxwell＇s electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge （DBD） plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry （PIV） experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around tile cylinder.

关键词： dielectric-barrier-discharge plasma body force flow around cylinder

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Investigation of vortical flow over bluff bodies with base cavities

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Acta Mechanica Sinica 2012年第5期28卷 1238-1247页

作者： Shu-Cheng Pan Jin-Sheng Cai National Key Laboratory of Aerodynamic Design and Research Northwestern Polytechnical University

Based on our previous research about drag reduction in term of the base cavity length using two dimensional simulations, this paper describes a numerical study of a bluff body of which the number of base cavities is successively increased and the cavity geometries are also modified to assume different shapes. Here we attempt to find an effective configuration to reduce the drag by increasing the number of base cavities. The numerical simulations examining varied number of base cavities reveal the presence of different strength of vortices in the wake zone which is the reason why the drag coefficients are distinctly different for different cases. In the case with double and triple rectangular cavities, we use the pressure contours snapshots at successive time instants to describe the wake evolution. We further investigate the effect of variable base cavity shapes for a constant cavity length at an identical time instant. A total of two different geometries of base cavities are discussed here： the rectangular and the sinusoidal cavities with sharp and rounded trailing edges, respectively. The numerical results reveal that the for- mer is an effective drag reduction configuration which can produce a significant base pressure recovery corresponding to the strength of the vortices shown in the pressure contour figures. While the latter shows no obvious reduction in drag coefficient and a similar intensity of vortex in the wake zone compared with the unmodified case. Reductions in drag are observed for all the investigated cavity configurations, and additionally it is found that the magnitude of the reduction bears a direct relationship with the number of the cavities up to a certain minimum value.

关键词： Flow control Drag reduction. Bluff body Basecavity

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A multiple-relaxation-time lattice Boltzmann method for high-speed compressible flows

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Chinese Physics B 2015年第5期24卷 262-269页

作者：李凯钟诚文 national key laboratory of Science and Technology on aerodynamic design and research Northwestern Polytechnical University

This paper presents a coupling compressible model of the lattice Boltzmann method. In this model, the multiplerelaxation-time lattice Boltzmann scheme is used for the evolution of density distribution functions, whereas the modified single-relaxation-time （SRT） lattice Boltzmann scheme is applied for the evolution of potential energy distribution functions. The governing equations are discretized with the third-order Monotone Upwind Schemes for scalar conservation laws finite volume scheme. The choice of relaxation coefficients is discussed simply. Through the numerical simulations, it is found that compressible flows with strong shocks can be well simulated by present model. The numerical results agree well with the reference results and are better than that of the SRT version.

关键词： lattice Boltzmann method multi-relaxation-time compressible flow finite volume method

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Far-field sonic boom prediction considering atmospheric turbulence effects: An improved approach

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Chinese Journal of Aeronautics 2022年第9期35卷 208-225页

作者： Jianling QIAO Zhonghua HAN Liwen ZHANG Wenping SONG Bifeng SONG Institute of aerodynamic and Multidisciplinary design Optimization School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710071China national key laboratory of Science and Technology on aerodynamic design and research School of AeronauticsNorthwestern Polytechnical UniversityXi'an710071China

Accurate prediction of sonic boom is one of key challenges for the design of a low-boom supersonic aircraft. For most of available far-field prediction methods, the effect of atmospheric turbulence appearing in the planetary boundary layer cannot be considered, which results in remarkable inaccuracy of predicting ground-level sonic boom waveform. Although some efforts have been made to overcome the shortcoming, the turbulence effects are not yet well described so far. This article proposes an improved method by extending the two-dimensional Heterogeneous One-Way Approximation for the Resolution of Diffraction(HOWARD) equation to account for the axial and transverse convections of wind fluctuation as well as the effect of temperature fluctuation. The proposed method is validated by comparing the predictions with the flight-test data of JAXA D-SEND#1 LBM, which shows that the result of the proposed method is in better agreement with the flight-test data than that of the method without considering atmospheric turbulence effects.Then, distortion mechanism of sonic boom waveforms caused by atmospheric turbulence is analyzed by using the proposed method. It is indicated that the effect of turbulent convection makes uniform sonic-boom wavefronts irregular, which creates the condition of diffraction effect to perturb waveforms. Finally, the proposed method is applied to investigate the behavior of two types of waveforms given by the sonic boom minimization theory. Results show that a far-field waveform with a weaker initial shock is more beneficial for low-boom design of a supersonic aircraft.

关键词： Atmospheric turbulence Augmented Burgers equation HOWARD equation Sonic boom Supersonic transport

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