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Generation of acoustic waves in the hypersonic boundary layer over a wavy wall

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Science China(Physics,Mechanics & Astronomy) 2022年第3期65卷 62-70页

作者： WenKai Zhu DingWei Gu YiDing Zhu CunBiao Lee State KeyLaboratory of Turbulence and Complex Systems Collaborative Innovation Center of Advanced Aero-EnginePeking UniversityBeijing 100871China

The effects of a wavy wall on a hypersonic boundary layer of a flared cone are investigated using experimental measurements and direct numerical simulations(DNSs). Non-contact optical measurements using a focused laser differential interferometer(FLDI) show that a wavy wall can significantly suppress the second mode, and multiple perturbations of new frequencies are generated over the wavy surface, which agrees well with numerical results. Using Lagrangian tracking of marked particles, it is demonstrated that the wavy wall geometry can induce mean flow oscillations while exciting acoustic waves. The frequencies of the excited disturbances over a wavy wall agree with the classical Rossiter model. The superposition of a disturbance propagating downstream and an acoustic wave propagating upstream at the same frequency but with different amplitudes and propagation velocities results in a spatial distribution with a streamwise-oscillatory pattern over the wavy surface. A simple two-wave superposition model that takes into account the phase velocities and wavenumbers of the convective disturbance and acoustic wave can well describe the modal behavior of excited disturbances over a wavy wall.

关键词： instability of boundary layers compressible flows hypersonic flows

A dual timescale model for micro-mixing and its application in LES-TPDF simulations of turbulent nonpremixed flames

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Chinese Journal of aeronautics 2019年第4期32卷 875-887页

作者： Fang WANG Rui LIU Li DOU Denghuan LIU Jie JIN aero-engine Numerical Simulation Research center School of Energy and Power EngineeringBeihang University Collaborative Innovation Center for Advanced Aero-Engine

The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transported Probability Density Function(TPDF) turbulence combustion model is promising in engineering applications. In flame region, the impact of chemical reaction should be considered in TPDF molecular mixing model. Based on pioneer research, three new TPDF turbulence-chemistry dual time scale molecular mixing models were proposed tentatively by adding the chemistry time scale in molecular mixing model for nonpremixed flame. The aero-engine Combustor Simulation Code(AECSC) which is based on LES-TPDF method was combined with the three new models. Then the Sandia laboratory's methane-air jet flames: Flame D and Flame E were simulated. Transient simulation results show that all the three new models can predict the instantaneous combustion flow pattern of the jet flames. Furthermore,the average scalar statistical results were compared with the experimental data. The simulation result of the new TPDF arithmetic mean modification model is the closest to the experimental data:the average error in Flame D is 7.6% and 6.6% in Flame E. The extinction and re-ignition phenomena of the jet flames especially Flame E were captured. The turbulence time scale and the chemistry time scale are in different order in the whole flow field. The dual time scale TPDF combustion model has ability to deal with both the turbulence effect and the chemistry reaction effect, as well as their interaction more accurately for nonpremixed flames.

关键词： Dual time scale model Large eddy simulation Sandia methane-air jet flame TPDF molecular mixing model Turbulence combustion model

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波纹壁面上的高超声速边界层气动降热

Science Bulletin 2022年第10期67卷 988-990页

作者：朱文凯顾丁炜司武飞陈十一朱一丁李存标 State Key Laboratory of Turbulence and Complex Systems Collaborative Innovation Center of Advanced Aero-EnginePeking UniversityBeijing 100871China

Hypersonic boundary layer transition is of fundamental importance for the design of high-speed vehicles because of its direct relevance to drag and aerodynamic heating.As the focus of transition and turbulence research is shifting towards higher velocities,research on compressible flows,especially hypersonic flows,is becoming increasingly attractive to researchers worldwide[1,2].

关键词： flows transition attractive

A combined application of micro-vortex generator and boundary layer suction in a high-load compressor cascade

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Chinese Journal of aeronautics 2019年第5期32卷 1171-1183页

作者： Shan MA Wuli CHU Haoguang ZHANG Xiangjun LI Haiyang KUANG School of Power and Energy Northwestern Polytechnical University collaborative innovation center of advanced aero-engine

In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex generator with a special configuration and the longitudinal suction slot are adopted. The calculated results show that a reverse flow region, which is considered the main reason for occurring stall at 7.9° incidence, grows and collapses rapidly near the leading edge and leads to two critical points occurring on the end-wall with the increasing incidence in the baseline. As the micro-vortex generator is introduced in the baseline cascade, the corner separation is switched to a trailing edge separation by the thrust from the induced vortex. Meanwhile, the occurrence of failure is delayed due to the mixed low energy fluid and main flow. The synergistic effects between the micro-vortex generator and the boundary layer suction on the performance of the cascade are superior to the baseline at all the incidence conditions before the occurrence of failure, and the sudden deterioration of the cascade occurs at 10.3° incidence. The optimal results show that the farther upstream suction position, the lower total pressure loss of the cascade with vortex generator at the near stall condition. Moreover, the induced vortex with a leg can migrate the accumulated low energy fluid backward to delay the occurrence of stall.

关键词： Boundary layer suction Flow control strategies High-load compressor cascade Numerical simulations Vortex generators

Recent progress in the study of transition in the hypersonic boundary layer

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National Science Review 2019年第1期6卷 155-170页

作者： Cunbiao Lee Shiyi Chen State Key Laboratory for Turbulence and Complex Systems Advanced Aero Engine Collaborative Innovation Center Peking University

Turbulence is a universal form of fluid motion. It is the key issue in fluid mechanics. Very recently, it has become a bottleneck in some key engineering research of national importance, such as aeronautics,astronautics and navigation. Developed turbulence and the onset of turbulence, i.e. transition, are two interrelated parts of turbulence. The hypersonic boundary-layer transition is a strategic focus in the fluid mechanics community. This article reviews recent developments in the study of the hypersonic boundary-layer transition, research facilities and experimental techniques. The hypersonic quiet wind tunnel is introduced as a necessary device to obtain real flight data in near space. Near-wall measurement techniques, such as temperature-sensitive paint, near-wall particle image velocimetry and Rayleigh-scattering visualization, are shown. The most important issues in the recent development of the transition in the hypersonic boundary layer are addressed. The instability and nonlinear interaction of different instability modes are discussed. The recent contributions from China, especially at Peking University, are also introduced.

关键词： hypersonic boundary layer transition quiet wind tunnel

Turbulent characteristics and rotation correction of wall function in rotating channel with high local rotation parameter

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Chinese Journal of aeronautics 2018年第10期31卷 1985-1999页

作者： Zhi TAO Huijie WU Ruquan YOU Haiwang LI Kuan WEI National Key Laboratory of Science and Technology on aero-engine aero-Thermodynamics Beihang University Collaborative Innovation Center for Advanced Aero-Engine Beihang University

The turbulent fluctuation and the rotation correction of wall function law are investigated in the entrance section of a rotating channel. The one-dimensional hot wire probe and the X-type probe are utilized to measure the boundary layer at four streamwise stations. Through the analysis on the boundary layer near the leading side and trailing side, it is found that the turbulent fluctuation is promoted in the trailing side whereas suppressed in the leading side. This difference is attributed to the Coriolis instability near the trailing side. In addition, considering the local rotation parameter Rc, whose maximum absolute value is 0.014, is larger than that in previous research, whose maximum value is 0.007, the whole process of the relaminarization is captured. To understand this phenomenon better, the effects of the generation term and the Coriolis term in the transport equation of the Reynolds stress are discussed. In addition, the rotation correction of the viscous-Coriolis region and the Coriolis region are discussed, a new revising method for the wall function is proposed.

关键词： Coriolis force Entry section Relaminarization Rotating channel Turbulence

Lock-in phenomenon of tip clearance flow and its influence on aerodynamic damping under specified vibration on an axial transonic compressor rotor

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Chinese Journal of aeronautics 2022年第3期35卷 185-200页

作者： Le HAN Dasheng WEI Yanrong WANG Mingchang FANG School of Energy and Power engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center for Advanced Aero-Engine Beijing 100083China

In this study,the lock-in phenomenon of Tip Clearance Flow(TCF)instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance.The capabilities of simulating instability flow and lock-in phenomenon are verified on a transonic rotor and a NACA0012 airfoil by comparing with the test data,respectively.The lock-in phenomenon is first numerically confirmed that may occur to TCF instabilities when its frequency is close to the blade vibration frequency.The lock-in region becomes wider with the vibration amplitude increasing,and it is also affected by modal shapes.For the rotor at the simulation conditions in this study,the bending mode results in a wider lock-in region than the torsional mode.In the lock-in region,the phase difference between the Tip Clearance Vortex(TCV)and the blade vibration changes with the flow condition and the frequency ratio of the blade vibration and the TCV instabilities.The frequency of the TCV instabilities reduces with the mass flow decreasing.Therefore,reducing mass flow and increasing frequency ratio have similar effects on the TCV phase,which causes a significant variation on the unsteady pressure amplitude in the blade tip area.Thus,the aerodynamic damping changes significantly with the TCV phase.The aerodynamic damping displays a nonlinear relationship with the vibration amplitude,and it changes from negative to positive with the vibration amplitude increasing at the same frequency ratio.The negative damping is mainly provided by the tip area of the blade.For unlocked conditions,the period of the TCF instabilities fluctuates over time,and it cannot be directly separated by their frequency features.Inter Blade Phase Angle(IBPA)also has an important influence on the feature of the TCV instabilities.The occurrence of frequency lock-in also requires“appropriate”IBPA.For the examined working conditions,the frequency lock-in occurs under 0 ND(Nodal Diameter),but not under 8 ND.However,no matter 0 ND or 8 ND,the phas

关键词： aerodynamic damping Inter blade phase angle Lock-in Specified blade vibration Tip clearance flow instabilities

Remaining useful life prediction for engineering systems under dynamic operational conditions: A semi-Markov decision process-based approach

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Chinese Journal of aeronautics 2019年第3期32卷 627-638页

作者： Diyin TANG Jinrong CAO Jinsong YU School of Automation Science and Electrical engineering Beihang University collaborative innovation center of advanced aero-engine

For critical engineering systems such as aircraft and aerospace vehicles, accurate Remaining Useful Life(RUL) prediction not only means cost saving, but more importantly, is of great significance in ensuring system reliability and preventing disaster. RUL is affected not only by a system's intrinsic deterioration, but also by the operational conditions under which the system is operating. This paper proposes an RUL prediction approach to estimate the mean RUL of a continuously degrading system under dynamic operational conditions and subjected to condition monitoring at short equi-distant intervals. The dynamic nature of the operational conditions is described by a discrete-time Markov chain, and their influences on the degradation signal are quantified by degradation rates and signal jumps in the degradation model. The uniqueness of our proposed approach is formulating the RUL prediction problem in a semi-Markov decision process framework, by which the system mean RUL can be obtained through the solution to a limited number of equations. To extend the use of our proposed approach in real applications, different failure standards according to different operational conditions are also considered. The application and effectiveness of this approach are illustrated by a turbofan engine dataset and a comparison with existing results for the same dataset.

关键词： Condition-specific failure threshold Degradation modeling Dynamic operational conditions Remaining useful life Semi-Markov decision process

Macro-phenomenological high-strain-rate elastic fracture model for ice-impact simulations

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Chinese Journal of aeronautics 2023年第3期36卷 146-160页

作者： Jiang FAN Qinghao YUAN Fulei JING Guangchen BAI Xiuli SHEN School of Energy and Power engineering Beihang UniversityBeijing 100191China Beijing Key Laboratory of aero-engine Structure and Strength Beijing 100191China collaborative innovation center of advanced aero-engine Beijing 100191China aero-engine Academy of China Aero Engine(Group)Corporation of ChinaBeijing 101304China

The ice impact can cause a severe damage to an aircraft’s exposed structure,thus,requiring its prevention.The numerical simulation represents an effective method to overcome this challenge.The establishment of the ice material model is critical.However,ice is not a common structural material and exhibits an extremely complex material behavior.The material models of ice reported so far are not able to accurately simulate the ice behavior at high strain rates.This study proposes a novel high-precision macro-phenomenological elastic fracture model based on the brittle behavior of ice at high strain rates.The developed model has been compared with five reported models by using the smoothed particle hydrodynamics method so as to simulate the ice-impact process with respect to the impact speeds and ice shapes.The important metrics and phenomena(impact force history,deformation and fragmentation of the ice projectile and deflection of the target)were compared with the experimental data reported in the literature.The findings obtained from the developed model are observed to be most consistent with the experimental data,which demonstrates that the model represents the basic physics and phenomena governing the ice impact at high strain rates.The developed model includes a relatively fewer number of material parameters.Further,the used parameters have a clear physical meaning and can be directly obtained through experiments.Moreover,no adjustment of any material parameter is needed,and the consumption duration is also acceptable.These advantages indicate that the developed model is suitable for simulating the iceimpact process and can be applied for the anti-ice impact design in aviation.

关键词： Crack propagation Elastic fracture High strain rate Ice impact Impact force Material model