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Instability analysis and drag coefficient prediction on a swept RAE2822 wing with constant lift coefficient

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Chinese Journal of Aeronautics 2017年第3期30卷 964-975页

作者： Zhenrong JING Zhangfeng HUANG department of Mechanics Tianjin University State Key Laboratory of aerodynamics China Aerodynamics Research and Development Center

Swept wing is widely used in civil aircraft,whose airfoil is chosen,designed and optimized to increase the cruise speed and decrease the drag *** parameters of swept wing,such as sweep angle and angle of attack,are determined according to the cruise lift coefficient requirement,and the drag coefficient is expected to be predicted accurately,which involves the instability characteristics and transition position of the *** pressure coefficient of the RAE2822 wing with given constant lift coefficient is obtained by solving the three-dimensional Navier-Stokes equation numerically,and then the mean flow is calculated by solving the boundary layer（BL） equation with spectral *** cross-flow instability characteristic of boundary layer of swept wing in the windward and leeward is analyzed by linear stability theory（LST）,and the transition position is predicted by *** drag coefficient is numerically predicted by introducing a laminar/turbulent indicator.A simple approach to calculate the lift coefficient of swept wing is *** is found that there is a quantitative relationship between the angle of attack and sweep angle when the lift coefficient keeps constant;when the angle of attack is small,the flow on the leeward of the wing is *** the angle of attack is larger than 3°,the flow becomes unstable quickly;with the increase of sweep angle or angle of attack the disturbance on the windward becomes more unstable,leading to the moving forward of the transition position to the leading edge of the wing;the drag coefficient has two significant jumping growth due to the successive occurrence of transition in the windward and the leeward;the optimal range of sweep angle for civil aircraft is suggested.

关键词： Constant lift coefficient Cross-flow instability Drag coefficient Linear stability theory Swept RAE2822 wing

High-Order Discontinuous Galerkin Method for Hovering Rotor Simulations Based on a Rotating Reference Frame

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第1期36卷 57-70页

作者： ZHANG Tao Lü Hongqiang QIN Wanglong CHEN Zhengwu department of aerodynamics Nanjing University of Aeronautics and Astronautics China aerodynamics Research and Development Center

An implicit higher ? order discontinuous Galerkin(DG) spatial discretization for the compressible Euler equations in a rotating frame of reference is presented and applied to a rotor in hover using hexahedral grids. Instead of auxiliary methods like grid adaptation,higher ? order simulations(fourth ? and fifth ? order accuracy) are *** numerical experiments are carefully designed,conducted and analyzed. The results show generally excellent consistence with references and vigorously demonstrate the higher?order DG method's better performance in loading distribution computations and tip vortex capturing, with much fewer degrees of freedom(DoF). Detailed investigations on the outer boundary conditions for hovering rotors are presented as well. A simple but effective speed smooth procedure is developed specially for the DG method. Further results reveal that the rarely used pressure restriction for outlet speed has a considerable advantage over the extensively adopted vertical speed restriction.

关键词： high-order method(HOM) discontinuous Glaerkin method(DGM) Euler equation hovering rotor simulation tip vortex

Optimal Design of Rectification Circuit in Electronic Circuit Fault Self-repair Based on EHW and RBT

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Chinese Journal of Electronics 2018年第1期27卷 93-101页

作者： ZHANG Junbin CAI Jinyan MENG Yafeng department of Electronic and Optical Engineering Mechanical Engineering College Hypervelocity aerodynamics Institute China Aerodynamics Research & Development Center

Reliability of traditional electronic circuit is improved mainly by redundant fault-tolerant technology with large hardware resource consumption and limited fault self-repair capability. In complicated environment,electronic circuit faults appear easily. If on-site immediate repair is not implemented, normal running of electronic system will be directly affected. In order to solve these problems, Evolvable hardware(EHW) technology is widely used. The conventional EHW has some *** optimal design of Rectification circuit(RTC) is further researched on the basis of the previously proposed fault self-repair based on EHW and Reparation balance technology(RBT). Fault sets are selected by fault danger degree and fault coverage rate. The optimal designed RTC can completely repair faults in the fault set. Simulation results prove that it has higher self-repair capability and less hardware resource.

关键词： Evolvable hardware(EHW) Fault self repair Reparation balance technology(RBT) Rectification circuit(RTC) Optimal design Fault coverage

Lift enhancement of airfoil and tip flow control for wind turbine

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Applied Mathematics and Mechanics(English Edition) 2011年第7期32卷 825-836页

作者：白亚磊马兴宇明晓 department of aerodynamics Nanjing University of Aeronautics and Astronautics

Two techniques that improve the aerodynamic performance of wind turbine airfoils are described. The airfoil $809, designed specially for wind turbine blades, and the airfoil FX60-100, having a higher lift-drag ratio, are selected to verify the flow control techniques. The flow deflector, fixed at the leading edge, is employed to control the boundary layer separation on the airfoil at a high angle of attack. The multi-island genetic algorithm is used to optimize the parameters of the flow deflector. The results indicate that the flow deflector can suppress the flow separation, delay the stall, and enhance the lift. The characteristics of the blade tip vortex, the wake vortex, and the surface pressure distributions of the blades are analyzed. The vortex diffuser, set up at the blade tip, is employed to control the blade tip vortex. The results show that the vortex diffuser can increase the total pressure coefficient of the core of the vortex, decrease the strength of the blade tip vortex, lower the noise, and improve the efficiency of the blade.

关键词： flow separation flow control flow deflector multi-island genetic algorithm,tip vortex diffuser

HB-2 high-velocity correlation model at high angles of attack in supersonic wind tunnel tests

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Chinese Journal of Aeronautics 2019年第7期32卷 1565-1576页

作者： Djordje VUKOVI? Dijana DAMLJANOVI? department of Experimental aerodynamics Military Technical InstituteVojnotehnicki Institut

Responding to a need for experimental data on a standard wind tunnel model at high angles of attack in the supersonic speed range, and in the absence of suitable reference data, a series of tests of two HB-2 standard models of different sizes was performed in the T-38 trisonic wind tunnel of Vojnotehnickˇi Institut(VTI), in the Mach number range 1.5–4.0, at angles of attack up to+30°. Tests were performed at relatively high Reynolds numbers of 2.2 millions to 4.5 millions(based on model forebody diameter). Results were compared with available low angle of attack data from other facilities, and, as a good agreement was found, it was assumed that, by implication, the obtained high angle of attack results were valid as well. Therefore, the results can be used as a reference database for the HB-2 model at high angles of attack in the supersonic speed range, which was not available before. The results are presented in comparison with available reference data, but also contain data for some Mach numbers not given in other publications.

关键词： Base pressure Experimental aerodynamics High angle of attack Standard model Wind tunnel

Implicit discontinuous Galerkin method on agglomerated high-order grids for 3D simulations

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Chinese Journal of Aeronautics 2016年第6期29卷 1496-1505页

作者： Qin Wanglong Lyu Hongqiang Wu Yizhao Zhou Shijie Chen Zhengwu department of aerodynamics Nanjing University of Aeronautics and AstronauticsNanjing 210016China China aerodynamics Research and Development Center Mianyang 621000China

High quality of geometry representation is regarded essential for high-order methods to maintain their high-order accuracy. An agglomerated high-order mesh generating method is investigated in combination with discontinuous Galerkin(DG) method for solving the 3D compressible Euler and Navier-Stokes equations. In this method, a fine linear mesh is first generated by standard commercial mesh generation tools. By taking advantage of an agglomeration method, a quadratic high-order mesh is quickly obtained, which is coarse but provides a high-quality geometry representation, thus very suitable for high-order computations. High-order discretizations are performed on the obtained grids with DG method and the discretized system is treated fully implicitly to obtain steady state solutions. Numerical experiments on several flow problems indicate that the agglomerated high-order mesh works well with DG method in dealing with flow problems of curved geometries. It is also found that with a fully implicit discretized system and a p-sequencing method, the DG method can achieve convergence state within several time steps which shows significant efficiency improvements compared to its explicit counterparts.

关键词： Agglomeration Discontinuous Galerkin(DG) High-order Implicit scheme Navier-Stokes equations

Installation error calibration for MEMS angular measurement system in hypersonic wind tunnel

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Chinese Journal of Aeronautics 2023年第5期36卷 175-186页

作者： Xiong WANG Xueling ZHAO Bin ZHOU Qi WEI Rong ZHANG Hypervelocity aerodynamics Institute China Aerodynamics Research and Development CenterMianyang 621000China department of Precision Instrument Tsinghua UniversityBeijing 100084China

The accuracy of model attitude measurement has an important impact on wind tunnel test results. Microelectromechanical System Inertial Measurement Unit(MEMS IMU) provides a feasible way to measure model attitudes with high accuracy. However, the installation error between MEMS IMU coordinate system and the body coordinate system of test models can make the accuracy of the model attitude measurement decrease. In wind tunnel tests, the installation error depends on the relationship between the IMU and the model mechanism before tests. Therefore, infield calibration in wind tunnel tests is necessary to reduce installation errors. To improve attitude measurement accuracy, the least squares quaternion calibration method based on MEMS IMU and six-position calibration procedure are proposed. High-precision three-axis turntable tests are performed. The pitch accuracy after calibration is higher than that before calibration in the angle of attack sweeping tests. The Root-Mean-Square Errors(RMSE) in the roll and yaw are within0.01°, which are smaller than those before calibration. In the roll sweeping tests, RMSE of three attitude angles decrease significantly. In hypersonic wind tunnel tests, the pitch errors before and after calibration are within 0.05° and 0.02° in the angle of attack sweeping tests without wind. In five angle of attack sweeping tests with wind, the deviation between the mean of the pitch and the pitch after the elastic angle correction is within 0.03° and the standard deviation of five tests is within 0.01°. The proposed method is confirmed to enhance the accuracy of attitude measurement effectively, which is convenient for engineering applications.

关键词： Calibration Installation error Least squares MEMS Model attitude measurement Quaternion Wind tunnel test

Nonlinear evolution of turbulent spots in the near-wall shear flow

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Science China(Physics,Mechanics & Astronomy) 2006年第2期49卷 158-168页

作者： ZHANG Li TANG Dengbin department of aerodynamics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of aerodynamics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The initial model of turbulent spots with the wall disturbance using the pulse form was proposed. A group of three-dimensional coupling compact difference schemes with high accuracy and high resolution were developed, and implemented to simulate the formation and development of turbulent spots in the near-wall shear flow by means of direct numerical simulation of the Navier-Stokes equations. Growing and decaying modes were used to analyze nonlinear evolution characteristics of the turbulent spots.

关键词： turbulent spots direct numerical simulation initial model nonlinear evolution.

Numerical and experimental investigation into hypersonic boundary layer transition induced by roughness elements

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Chinese Journal of Aeronautics 2019年第3期32卷 559-567页

作者： Hao DONG Shicheng LIU Xi GENG Song LIU Liming YANG Keming CHENG department of aerodynamics Nanjing University of Aeronautics and Aeronautics department of Mechanical Engineering National University of Singapore

In this work, the Direct Numerical Simulation(DNS) and Oil-Film Interferometry(OFI)technique are used to investigate the hypersonic boundary layer transition induced by single and double roughness elements at Mach number 5. For single roughness, the DNS results showed that both horseshoe vortices and hairpin vortices caused by shear layer instability can affect the boundary layer instability. The generation of the near-wall unstable structure is the key point of boundary layer transition behind the roughness element. At the downstream of the roughness element, the interaction between horseshoe vortices and hairpin vortices will spread in the spanwise *** double roughness elements, the effect of the spacing between roughness elements on the transition is studied. It is found that the case of higher spacing between roughness elements is more effective for inducing transition than the lower one. The interaction between two adjacent roughness elements can suppress the evolution of horseshoe vortices in the downstream and trigger the instability of shear layer. Thus, the transition will be suppressed accordingly.

关键词： Boundary layer transition Hypersonic Direct numerical simulation (DNS) Oil-film interferometry Roughness elements