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Aeroelastic stability analysis of heated flexible panel subjected to an oblique shock

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Chinese Journal of Aeronautics 2018年第8期31卷 1650-1666页

作者： Liuqing ye zhengyin ye Xiaochen WANG School of Aeronautics Northwestern Polytechnical University Xi'an 710072 China

The critical conditions for aeroelastic stability and the stability boundaries of a flexible two-dimensional heated panel subjected to an impinging oblique shock are considered using theoretical analysis and numerical computations, respectively. The von-Karman large deflection theory of isotropic flat plates is used to account for the geometrical nonlinearity of the heated panel, and local first-order piston theory is employed in the region before and after shock waves to estimate the aerodynamic pressure. The coupled partial differential governing equations, according to the Hamilton principle, are established with thermal effect based on quasi-steady thermal stress *** Galerkin discrete method is employed to truncate the partial differential equations into a set of ordinary differential equations, which are then solved by the fourth-order Runge-Kutta numerical integration method. Lyapunov indirect method is applied to evaluate the stability of the heated panel. The results show that a new aeroelastic instability（distinct from regular panel flutter） arises from the complex interaction of the incident and reflected wave system with the panel flexural modes and thermal loads. What＇s more, stability of the panel is reduced in the presence of the oblique shock. In other words, the heated panel becomes aeroelastically unstable at relatively small flight aerodynamic pressure.

关键词： AerothermoelasticityHeated panel Local piston theory Shock waves Stability Thermal flutter

Investigation on the mechanism of aeroelastic hazard during ground test of rocket nozzle

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Science China(Technological Sciences) 2012年第9期55卷 2462-2473页

作者： LU GuangLiang ye zhengyin State Key Laboratory of Aerodynamic Design and Research Northwest Polytechnical UniversityXi'an 710072China

Side loads and aeroelastic stability of rocket nozzle were studied by solving Navier-Stokes equation coupled with structural equation of *** computation was implemented at different total pressure inlet conditions,and flow phenomena of free shock separation(FSS) and restricted shock separation(RSS) were *** certain total pressure inlet conditions,it was found that both kinds of separations existed in nozzle flow filed,while RSS exhibited combined space asymmetry and time unsteady *** corresponding asymmetric circumferential pressure distribution,strong pressure fluctuation in separation region and large range of displacement of shock wave all led to severe side ***,for flexible nozzles,the low pressure gradient in separation region might reduce structure stability at nozzle exit,resulting in large local *** was also found that aeroelasticity exhibited buffeting characteristic due to the asymmetric separation,resulting in reduction of aeroelastic stability,even structure ***,aeroelasticity might amplify side loads and aggravate its growth ***,with increment of inlet pressure,nozzle aeroelastic stability was also increased when a full flow was nearly reached.

关键词： aeroelasticity rocket nozzle flow separation side loads stability

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 *** 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 *** means of the large eddy simulation(LES)with high-order accurate finite difference method,the numerical investigations are *** 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 *** 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 ***,it is indicated that a surface with large resistance for spanwise flow and small resistance for streamwise flow can achieve significant drag *** 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

Numerical simulation of rotor-airframe aerodynamic interaction based on unstructured dynamic overset grids

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Science China(Technological Sciences) 2012年第10期55卷 2798-2807页

作者： XU HeYong ye zhengyin National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical UniversityXi’an 710072China

A method of unstructured dynamic overset grids is developed for the numerical simulation of helicopter unsteady rotorairframe aerodynamic *** the effective treatment of the relative motion between the rotor and the airframe,the domain of flowfield is divided into two overset subzones,namely,a rotational subzone containing the blades and a stationary subzone containing the *** overset part of two subzones is used to convect the flow variables of the two *** Taylor series expansion is used to obtain a second-order spatial accuracy,and dual-time stepping is adopted to improve the solution *** deformation from the blade motion in forward flight is treated by using a spring *** is made by numerically simulating the flows around a wind tunnel configuration and comparing the predicted time-averaged and instantaneous inflow and airframe surface pressure distributions with the experimental *** shows that the present method is efficient and robust for the prediction of complicated unsteady rotor-airframe aerodynamic interaction phenomena.

关键词： unstructured grid overset grids rotor-airframe interaction spring analogy relative motion

Experimental and computational investigation of novel vertical tail buffet suppression method for high sweep delta wing

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Science China(Technological Sciences) 2015年第1期58卷 147-157页

作者： ZHANG Qing HUA RuHao ye zhengyin School of Aeronautics Northwestern Polytechnical University

Our research aim is to investigate the buffet alleviation effect of static or vibrating bulges attached on the forebody surface of the *** and numerical simulations on a model consisting of a sharp-edged,70°-leading edge sweep delta wing and twin swept back vertical tails were *** with different bulges were tested and computed at 10 and 20 m/s of free stream velocity at angles of attack ranging from 20°–50°.Dynamic strain gauge and multichannel data acquisition and analysis system were employed for the measurement of unsteady root strain on the vertical *** and computational results show that both static and vibrating bulges behave effectively as a novel tool to alleviate tail buffet,and the alleviation effect depends largely on the vibrating ***,one-sided bulge can only alleviate the buffeting response for the tail of the same side,and it has no obvious alleviation effect for the opposite *** of the spectral analysis reveal that there are generally three peaks of spectral density for aircrafts of this configuration,and bulges used in this paper could alleviate tail buffeting,but the total lift and drag of the whole model show no obvious deviation compared to the base model and the dominant frequency of the vibration of the tails has not shifted.

关键词： forebody bulge delta wing/twin tail configuration vortex breakdown self-induction theory buffet suppression

Design of a new tandem wings hybrid airship

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Science China(Physics,Mechanics & Astronomy) 2012年第10期55卷 1886-1893页

作者： LI Feng ye zhengyin GAO Chao National Key Loboratory of Aerodynamic Design and Research Northwestern Polytechnical UniversityXi'an 710072China

It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude *** the numerical method,a new tandem wings hybrid airship with both higher utility value and economy efficiency was obtained and its total performance and technical parameters were analyzed in *** order to further improve the lift-drag characteristics,we implemented the optimization design for aerodynamic configuration of tandem wings hybrid airship via the response surface *** results indicate that the tandem wings hybrid airship has considerable volume efficiency and higher aerodynamic *** optimization,the lift-drag ratio of this hybrid airship was increased by 6.08%.In a given gross lift condition,tandem wings hybrid airship may provide more payload and specific ***,the size of tandem airship is smaller so the demand for skin flexible materials can be *** of this study could serve as a new approach to designing buoyancy-lifting integrated hybrid airship.

关键词： hybrid airship tandem wings numerical simulation aerodynamic configuration optimization design

Sparse grid-based polynomial chaos expansion for aerodynamics of an airfoil with uncertainties

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Chinese Journal of Aeronautics 2018年第5期31卷 997-1011页

作者： Xiaojing WU Weiwei ZHANG Shufang SONG zhengyin ye School of Aeronautics Northwestern Polytechnical University

The uncertainties can generate fluctuations with aerodynamic characteristics. Uncertainty Quantification（UQ） is applied to compute its impact on the aerodynamic *** addition, the contribution of each uncertainty to aerodynamic characteristics should be computed by uncertainty sensitivity analysis. Non-Intrusive Polynomial Chaos（NIPC） has been successfully applied to uncertainty quantification and uncertainty sensitivity analysis. However, the non-intrusive polynomial chaos method becomes inefficient as the number of random variables adopted to describe uncertainties increases. This deficiency becomes significant in stochastic aerodynamic analysis considering the geometric uncertainty because the description of geometric uncertainty generally needs many parameters. To solve the deficiency, a Sparse Grid-based Polynomial Chaos（SGPC） expansion is used to do uncertainty quantification and sensitivity analysis for stochastic aerodynamic analysis considering geometric and operational uncertainties. It is proved that the method is more efficient than non-intrusive polynomial chaos and Monte Carlo Simulation（MSC） method for the stochastic aerodynamic analysis. By uncertainty quantification, it can be learnt that the flow characteristics of shock wave and boundary layer separation are sensitive to the geometric uncertainty in transonic region. The uncertainty sensitivity analysis reveals the individual and coupled effects among the uncertainty parameters.

关键词： Non-intrusive polynomial chaos sparse grid Stochastic aerodynamic analysis analysis Unceriainty quantification

Characteristic analysis of lock-in for an elastically suspended airfoil in transonic buffet flow

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Chinese Journal of Aeronautics 2016年第1期29卷 129-143页

作者： Quan Jingge Zhang Weiwei Gao Chuanqiang ye zhengyin School of Aeronautics Northwestern Ploytechnical University

Numerical simulations are performed to study the aeroelastic responses of an elastically suspended airfoil in transonic buffet flow, by coupling the unsteady Reynolds-averaged Navier- Stokes （RANS） equations and structural motion equation. The current work focuses on the char- acteristic analysis of the lock-in phenomenon. Great attentions are paid to studying the frequency range of lock-in and the effects of the three parameters, namely the structural natural frequency, mass ratio and structural damping, on lock-in characteristic of the elastic system in detail. It is found that when the structural natural frequency is close to the buffet frequency, the coupling fre- quency of the elastic system is no longer equal to the buffet frequency, but keeps the same value as the structural natural frequency. The frequency lock-in occurs and stays present until the structural nature frequency is near the double buffet frequency. It means that the lock-in presents within a broad range, of which the lower threshold is near the buffet frequency, while the upper threshold is near the double buffet frequency. Moreover, the frequency range of lock-in is affected by mass ratio and structural damping. The lower the mass ratio and structural damping are, the wider the range of lock-in will be. The upper threshold of lock-in grows with the mass ratio and structural damping decreasing, but the lower threshold always keeps the same.

关键词： Aeroelastic analysisBuffet Elastic airfoil Lock-in Transonic flow

Numerical study on the correlation of transonic single-degree-of-freedom flutter and buffet

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Science China(Physics,Mechanics & Astronomy) 2015年第8期58卷 67-78页

作者： GAO ChuanQiang ZHANG WeiWei LIU YiLang ye zhengyin JIANG YueWen School of Aeronautics Northwestern Polytechnical University Department of Engineering Science University of Oxford

Transonic single-degree-of-freedom(SDOF) flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are investigated using Unsteady Reynolds-Averaged Navier-Stokes(URANS) equations. The airfoil is free to vibrate in SDOF of pitching. It is found that, the coupling system may be unstable and SDOF self-excited pitching oscillations occur in pre-buffet flow condition, where the free-stream angle of attack(AOA) is lower than the buffet onset of a stationary airfoil. In the theory of classical aeroelasticity, this unstable phenomenon is defined as flutter. However, this transonic SDOF flutter is closely related to transonic buffet(unstable aerodynamic models) due to the following reasons. Firstly, the SDOF flutter occurs only when the free-stream AOA of the spring suspended airfoil is slightly lower than that of buffet onset, and the ratio of the structural characteristic frequency to the buffet frequency is within a limited range. Secondly, the response characteristics show a high correlation between the SDOF flutter and buffet. A similar "lock-in" phenomenon exists, when the coupling frequency follows the structural characteristic frequency. Finally, there is no sudden change of the response characteristics in the vicinity of buffet onset, that is, the curve of response amplitude with the free-stream AOA is nearly smooth. Therefore, transonic SDOF flutter is often interwoven with transonic buffet and shows some complex characteristics of response, which is different from the traditional flutter.

关键词： transonic flow single-degree-of-freedom flutter transonic buffet buffet onset correlation