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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 ***-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 *** 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 *** 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 *** parallel computing considering automatic load balance on averagely partitioned overset grid is developed to reduce the wall-clock time of an unsteady *** 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 *** 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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Attenuation of boundary-layer instabilities for natural laminar flow design on supersonic highly swept wings

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Chinese Journal of Aeronautics 2024年第11期37卷 118-137页

作者： han NIE Wenping SONG zhonghua han Kefeng ZHENG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Aircraft Configuration Design Xi’an 710072China

To meet the challenge of drag reduction for next-generation supersonic transport aircraft,increasing attention has been focused on Natural Laminar Flow(NLF)***,the highly swept wings and high-Reynolds-number conditions of such aircraft dramatically amplify Crossflow(CF)instabilities inside boundary layers,making it difficult to maintain a large laminar flow *** explore novel NLF designs on supersonic wings,this article investigates the mechanisms underlying the attenuation of Tollmien-Schlichting(TS)and CF instabilities by modifying pressure *** evolution of TS and CF instabilities are evaluated under typical pressure distributions with different leading-edge flow acceleration region lengths,pressure coefficient slopes and pressure coefficient *** results show that shortening the leading-edge flow acceleration region and using a flat pressure distribution are favorable for suppressing CF instabilities,and keeping a balance of disturbance growth between positive and negative wave angles is favorable for attenuating TS *** on the uncovered mechanisms,a strategy of supersonic NLF design is *** of the proposed strategy at a 60°sweep angle and Ma=2 presents potential to exceed the conventional NLF limit and achieve a transition Reynolds number of 17.6million,which can provide guidance for NLF design on supersonic highly swept wings.

关键词： Supersonic transport aircraft Natural laminar flow design Supersonic flow Highly-swept wings Transition delay Linear stability theory

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Aerodynamic/aeroacoustic variable-fidelity optimization of helicopter rotor based on hierarchical Kriging model

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Chinese Journal of Aeronautics 2020年第2期33卷 476-492页

作者： Yuepeng BU Wenping SONG zhonghua han Yu ZhanG Liang ZhanG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

Rotor noise is one of the most important reasons for restricting helicopter development;hence,the optimization design of rotor blade considering aeroacoustic and aerodynamic performance at the same time has always been the focus of research *** complex rotor design problems with a large number of design variables,the efficiency of the traditional Kriging model needs to be ***,Hierarchical Kriging(HK)model is employed in this study for rotor optimization *** using the validated RANS solver and acoustic method based on the FWHpds equation,an efficient aerodynamic/aeroacoustic optimization method for high-dimensional problem of rotors in hover based on HK model is *** using present HK model and new infill-sampling criteria,the number of design variables is increased from less than *** of two analytical function test cases show that the HK model is efficient and accurate in ***,the helicopter rotor blade is optimally designed for aerodynamic/aeroacoustic performance in hover based on the HK model with high dimensional design *** objective function is adopted to improve the rotational noise characteristics by reducing the absolute peak of the acoustic *** addition,the constraints of thrust,hover efficiency,solidity,and airfoils thickness are strictly *** results show that the Kriging model finds the objective of reducing the noise by 2.87 dB after 248 iterations while the HK model does it only after 164 *** optimization efficiency of the HK model is significantly higher than that of the traditional Kriging *** the case analyzed,the HK model saves 35%of the time used by the Kriging model.

关键词： Aeroacoustics Design optimization FW-Hpds equation Helicopter rotor RANS equations

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Aerodynamic performance enhancement forflapping airfoils by co-flow jet

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Chinese Journal of Aeronautics 2020年第10期33卷 2535-2554页

作者： Tao WU Bifeng SONG Wenping SONG Wenqing YANG zhonghua han School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Yangtze River Delta Research Institute Northwestern Polytechnical UniversityTaicang 215400China Research&Development Institute Northwestern Polytechnical University in ShenzhenShenzhen 518057China

Introducing active flow control into the design of flapping wing is an effective way to enhance its aerodynamic *** this paper,a novel active flow control technology called Co-Flow Jet(CFJ)is applied to flapping *** effect of CFJ on aerodynamic performance of flapping airfoils at low Reynolds number is numerically investigated using Unsteady Reynolds Averaged Navier-Stokes(URANS)simulation with Spalart-Allmaras(SA)turbulence *** methods are validated by a NACA6415-based CFJ airfoil case and a S809 pitching airfoil *** NACA6415 baseline airfoil and NACA6415-based CFJ airfoil with jet-off and jet-on are simulated in flapping motion,with Reynolds number 70,000 and reduced frequency *** a result,CFJ airfoils with jet-on generally have better lift and thrust characteristics than baseline airfoils and jet-off airfoil when Cμgreater than 0.04,which results from the CFJ effect of reducing flow separation by injecting high-energy fluid into boundary ***,typical kinematic and geometric parameters,including the reduced frequency and the positions of the suction and injection slot,are systematically studied to figure out their influence on aerodynamic performance of the CFJ *** a variable Cμjet control strategy is proposed to further improve effective propulsive *** with using constant Cμ,an increase of effective propulsive efficiency by22.6%has been achieved by using prescribed variable CμNACA6415-based CFJ airfoil at frequency *** study may provide some guidance to performance enhancement for Flapping wing Micro Air Vehicles(FMAV).

关键词： Aerodynamic performance Co-flow jet Flapping airfoils Flow control Propulsive efficiency

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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 ***, 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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A transition prediction method for flow over airfoils based on high-order dynamic mode decomposition

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Chinese Journal of Aeronautics 2019年第11期32卷 2408-2421页

作者： Mengmeng WU zhonghua han han NIE Wenping SONG Soledad Le CLAINCHE Esteban FERRER School of Aeronautics Northwestern Poly technical UniversityX i’an 710072China ETSIAE-UPM School of AeronauticsUniversidad Politecnica de MadridPza Cardenal Cisneros 3Spain

This article presents a novel approach for predicting transition locations over airfoils,which are used to activate turbulence model in a Reynolds-averaged Navier-Stokes flow *** approach combines Dynamic Mode Decomposition(DMD)with e^*** core idea is to use a spatial DMD analysis to extract the modes of unstable perturbations from a steady flowfield and substitute the local Linear Stability Theory(LST)analysis to quantify the spatial growth of Tollmien–Schlichting(TS)*** is assumed to take place at the stream-wise location where the most amplified mode’s N-factor reaches a prescribed threshold and a turbulence model is activated *** improve robustness,the high-order version of DMD technique(known as HODMD)is employed.A theoretical derivation is conducted to interpret how a spatial highorder DMD analysis can extract the growth rate of the unsteady *** new method is validated by transition predictions of flows over a low-speed Natural-Laminar-Flow(NLF)airfoil NLF0416 at various angles of attack and a transonic NLF airfoil *** transition locations predicted by our HODMD/e^Nmethod agree well with experimental data and compare favorably to those obtained by some existing methods■.It is shown that the proposed method is able to predict transition locations for flows over different types of airfoils and offers the potential for application to 3D wings as well as more complex configurations.

关键词： Airfoil Dynamic mode decomposition(DMD) e^N criterion Navier-Stokes equations Transition prediction

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Efficient aerodynamic shape optimization using variable-fidelity surrogate models and multilevel computational grids

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Chinese Journal of Aeronautics 2020年第1期33卷 31-47页

作者： zhonghua han Chenzhou XU Liang ZhanG Yu ZhanG Keshi ZhanG Wenping SONG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

A variable-fidelity method can remarkably improve the efficiency of a design optimization based on a high-fidelity and expensive numerical simulation,with assistance of lower-fidelity and cheaper simulation(s).However,most existing works only incorporate‘‘two"levels of fidelity,and thus efficiency improvement is very *** order to reduce the number of high-fidelity simulations as many as possible,there is a strong need to extend it to three or more *** article proposes a novel variable-fidelity optimization approach with application to aerodynamic *** key ingredient is the theory and algorithm of a Multi-level Hierarchical Kriging(MHK),which is referred to as a surrogate model that can incorporate simulation data with arbitrary levels of *** high-fidelity model is defined as a CFD simulation using a fine grid and the lower-fidelity models are defined as the same CFD model but with coarser grids,which are determined through a grid convergence ***,sampling shapes are selected for each level of fidelity via technique of Design of Experiments(DoE).Then,CFD simulations are conducted and the output data of varying fidelity is used to build initial MHK models for objective(e.g.C_D)and constraint(e.g.C_L,C_m)***,new samples are selected through infillsampling criteria and the surrogate models are repetitively updated until a global optimum is *** proposed method is validated by analytical test cases and applied to aerodynamic shape optimization of a NACA0012 airfoil and an ONERA M6 wing in transonic *** results confirm that the proposed method can significantly improve the optimization efficiency and apparently outperforms the existing single-fidelity or two-level-fidelity method.

关键词： Aerodynamic shape optimization Computational fluid dynamics Hierarchical kriging Kriging Surrogate model

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Application of surrogate models to stability analysis and transition prediction in hypersonic flows

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Advances in Aerodynamics 2022年第1期4卷 699-720页

作者： han Nie Wenping Song zhonghua han Guohua Tu Jianqiang Chen National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical UniversityXi’an710072People’s Republic of China China Aerodynamics Research and Development Center Mianyang621000People’s Republic of China

To increase the efficiency and robustness of stability-based transition prediction in flow simulations, simplified methods are introduced to substitute direct stability analyses for rapid disturbance growth prediction. For low-speed boundary layers, these methods are mainly established based on self-similar assumptions, which are not applicable to non-similar boundary layers in hypersonic flows. The objective of this article is to investigate the application of surrogate models to stability analysis of non-similar flows over blunt cones, focused on parameterization of boundary-layer (BL) profiles. Firstly, correlations between BL edge and profile parameters are analyzed, along with self-similar flow parameters and discrete points on BL profiles, which present four groups of BL characteristic parameters. Secondly, using these parameters as inputs, surrogate models are built for disturbance growth prediction over an MF-1 blunt cone. Results show that, surrogate models using four BL edge parameters and a BL shape factor {Ue, Te, ρe, ηe, H12} for stability analysis can achieve comparable accuracy with those using 16 discrete BL profile parameters, which are more precise than those using merely self-similar parameters or BL edge parameters. Thirdly, the established surrogate models are validated by stability analysis and transition prediction over the MF-1 blunt cone in flight experiments at the instants of t = 17 s ~ 22 s. Compared with direct linear stability analyses, the mean relative error of predicted disturbance growth rates by surrogate models is 8.0% and the maximum relative error of N factor envelopes is 6.6%, which indicates feasible applications of surrogate models to stability analysis and transition prediction of non-similar boundary layers in hypersonic flows.

关键词： Surrogate models Stability analysis Transition prediction Hypersonic flows Blunt cone

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Lift performance enhancement for flapping airfoils by considering surging motion

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Chinese Journal of Aeronautics 2022年第9期35卷 194-207页

作者： Tao WU Bifeng SONG Wenping SONG Wenqing YANG Dong XUE zhonghua han School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China Yangtze River Delta Research Institute of Northwestern Polytechnical University Taicang 215400China

The flapping motion has a great impact on the aerodynamic performance of flapping wings. In this paper, a surging motion is added to an airfoil performing pitching-plunging combined motion to figure out how it influences the lift performance and flow pattern of flapping ***, the numerical methods are validated by a NACA0012 airfoil pitching case and a NACA0012 airfoil plunging case. Then, the E377m airfoil which has typical geometric characteristics of the bird-like airfoil is selected as the calculation model to study how phase differences φ1 between surging motion and plunging motion affect the aerodynamic performance of flapping airfoils. The results show that the airfoil with surging motion has comprehensively better lift performance and thrust performance than the airfoil without surging motion when 15°hanism that surging motion adjusts the aerodynamic force is analyzed in detail by comparing the vortex structure and kinematic parameters. The results of this paper help reveal the aerodynamic mechanism of bird flight and guide the design of Flapping wing Micro Air Vehicles(FMAV).

关键词： Aerodynamics Flapping airfoils Surging motion Trajectory optimization Unsteady flow

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Effect of longitudinal lift distribution on sonic boom of a canard-wing-stabilator-body configuration

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Chinese Journal of Aeronautics 2023年第6期36卷 92-108页

作者： Liwen ZhanG zhonghua han Jianling QIAO Wenping SONG Yulin DING Xuehe WANG Institute of Aerodynamic and Multidisciplinary Design Optimization School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710072China National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710072China Research Center for Environment-friendly Supersonic Civil Transport Northwestern Polytechnical UniversityXi'an 710072China

After the last flight of the Concorde in 2003,sonic boom has been one of the obstacles to the return of a supersonic transport aircraft to *** reduce the sonic boom intensity to an acceptable level,it is of great significance to study the effect of lift distribution on far-field sonic boom,since lift is one of the most important contributors to an intense sonic *** studies on the longitudinal lift distribution used low-fidelity methods,such as Whitham theory,and in turn,only preliminary conclusions were obtained,such as that extending the lift distribution can reduce sonic *** paper uses a newly developed high-fidelity prediction method to quantitatively study the effect of longitudinal lift distribution on the sonic boom of a Canard-Wing-Stabilator-Body(CWSB)*** high-fidelity prediction method combines near-feld CFD simulation with far-field propagation by solving the augmented Burgers equation.A multipole analysis method is employed for the extraction of near-field waveform in order to reduce computational *** configurations with the same total lift but different distributions are studied,and the quantitative relationship between the longitudinal lift distribution and far-field sonic boom intensity is *** is observed that a small lift generated by the stabilator can prevent aft-stabilator and aft-fuselage shocks from merging,while the balanced lift generated by the canard and wing can effectively keep the corresponding shocks further apart,which is beneficial for reducing both the on-track and off-track sonic *** turn,the acoustic level perceived at the ground can be reduced by 5.9 PLdB on-track and 5.4 PLdB off-track,on average.

关键词： Computational fluid dynamics Longitudinal lift distribution Sonic boom Sonic boom reduction Supersonic transport

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