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EXPERIMENTAL INVESTIGATION ON THE TURBULENT COHERENT STRUCTURES OF LAMINAR SEPARATION FLOW OVER A BACKWARD FACING STEP
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作者 Wang Jinjun Lian Qixiang Lan Shilong(Fluid Mechanics Institute, Beijing University of Aeronautics and Astronautics, Beijing, China, 100083) 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 1996年第3期175-181,共7页
The experimental investigation is conducted with LDV and hydrogen bubble technique in water flow. The shear layer thickness. the vorticity thickness. the maximulll value of turbulence intensities. the turbulent coher... The experimental investigation is conducted with LDV and hydrogen bubble technique in water flow. The shear layer thickness. the vorticity thickness. the maximulll value of turbulence intensities. the turbulent coherent structure. the variations of wall shear stress and the boundary layer shape factor are obtained. In the redevelopment region. the detailed analysis is first made for the streak structures in the near wall region and the turbulent boundary layer is formed at (x-xr) / h = 20. 展开更多
关键词 backward facing steps laminar boundary layer separated flow turbulent boundary layer reattached flow
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Investigation of the interaction between NS-DBD plasma-induced vortexes and separated flow over a swept wing
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作者 刘备 梁华 郑博睿 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第1期88-99,共12页
The effect of nanosecond pulsed dielectric barrier discharge(NS-DBD) plasma flow separation control is closely related to the actuation frequency,because it involves the interaction between plasma-induced vortexes and... The effect of nanosecond pulsed dielectric barrier discharge(NS-DBD) plasma flow separation control is closely related to the actuation frequency,because it involves the interaction between plasma-induced vortexes and separated flow.In order to study the mechanism of NS-DBD plasma flow separation control over a swept wing,especially the influence of the actuation frequency,at first,experimental studies of the actuation frequencies at 100 Hz are conducted to validate the numerical simulation method.Then,numerical studies of different actuation frequencies which are 50 Hz,100 Hz,160 Hz,200 Hz,500 Hz,and 1000 Hz,respectively are conducted.The interaction between the plasma-induced vortexes and the separated flow is analyzed.Results show that there is a range of the actuation frequency which includes the frequency(160 Hz) calculated by the average aerodynamic chord length to make the control effect good,but when the actuation frequencies are too low(50 Hz) or too high(1000 Hz),the control effect will get worse.The former is because plasmainduced vortexes disappear in a period within an actuation cycle;the latter is because plasma-induced vortexes cannot develop completely,resulting in a weak vortex intensity. 展开更多
关键词 plasma-induced vortex flow separation control NS-DBD LES
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Analysis of flow separation control using nanosecond-pulse discharge plasma actuators on a flying wing 被引量:4
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作者 Zheng LI Zhiwei SHI +3 位作者 Hai DU Qijie SUN Chenyao WEI Xi GENG 《Plasma Science and Technology》 SCIE EI CAS CSCD 2018年第11期116-125,共10页
Dielectric barrier discharge (DBD) plasma is one of most promising flow control method for its several advantages. The present work investigates the control authority of nanosecond pulse DBD plasma actuators on a fl... Dielectric barrier discharge (DBD) plasma is one of most promising flow control method for its several advantages. The present work investigates the control authority of nanosecond pulse DBD plasma actuators on a flying wing model's aerodynamic characteristics. The aerodynamic forces and moments are studied by means of experiment and numerical simulation. The numerical simulation results are in good agreement with experiment results. Both results indicate that the NS-DBD plasma actuators have negligible effect on aerodynamic forces and moment at the angles of attack smaller than 16-. However, significant changes can be achieved with actuation when the model's angle of attack is larger than 16° where the flow separation occurs. The spatial flow field structure results from numerical simulation suggest that the volumetric heat produced by NS-DBD plasma actuator changes the local temperature and density and induces several vortex structures, which strengthen the mixing of the shear layer with the main flow and delay separation or even reattach the separated flow. 展开更多
关键词 nanosecond dielectric barrier discharge flying wing aircraft flow separation control
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Flow Separation and Vortex Dynamics in Waves Propagating over A Submerged Quartercircular Breakwater 被引量:2
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作者 JIANG Xue-lian YANG Tian +1 位作者 ZOU Qing-ping GU Han-bin 《China Ocean Engineering》 SCIE EI CSCD 2018年第5期514-523,共10页
The interactions of cnoidal waves with a submerged quartercircular breakwater are investigated by a ReynoldsAveraged Navier–Stokes(RANS) flow solver with a Volume of Fluid(VOF) surface capturing scheme(RANSVOF) model... The interactions of cnoidal waves with a submerged quartercircular breakwater are investigated by a ReynoldsAveraged Navier–Stokes(RANS) flow solver with a Volume of Fluid(VOF) surface capturing scheme(RANSVOF) model. The vertical variation of the instantaneous velocity indicates that flow separation occurs at the boundary layer near the breakwater. The temporal evolution of the velocity and vorticity fields demonstrates vortex generation and shedding around the submerged quartercircular breakwater due to the flow separation. An empirical relationship between the vortex intensity and a few hydrodynamic parameters is proposed based on parametric analysis. In addition, the instantaneous and time-averaged vorticity fields reveal a pair of vortices of opposite signs at the breakwater which are expected to have significant effect on sediment entrainment, suspension, and transportation,therefore, scour on the leeside of the breakwater. 展开更多
关键词 submerged quartercircular breakwater cnoidal wave flow separation vortex dynamics SCOUR
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A Lagrangian criterion of unsteady flow separation for two-dimensional periodic flows 被引量:2
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作者 Shuaibin HAN Shuhai ZHANG Hanxin ZHANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第7期1007-1018,共12页
The present paper proposes a Lagrangian criterion of unsteady flow separation for two-dimensional periodic flows based on the principle of weighted averaging zero skin-friction given by Haller (HALLER, G. Exact theor... The present paper proposes a Lagrangian criterion of unsteady flow separation for two-dimensional periodic flows based on the principle of weighted averaging zero skin-friction given by Haller (HALLER, G. Exact theory of unsteady separation for two-dimensional flows. Journal of Fluid Mechanics, 512, 257-311 (2004)). By analyzing the distribution of the finite-time Lyapunov exponent (FTLE) along the no-slip wall, it can be found that the periodic separation takes place at the point of the zero FTLE. This new criterion is verified with an analytical solution of the separation bubble and a numerical simulation of lid-driven cavity flows. 展开更多
关键词 Lagrangian criterion unsteady flow separation finite-time Lyapunov ex-ponent(FTLE) two-dimensional periodic flow
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Experimental Investigation of Flow Separation Control Using Dielectric Barrier Discharge Plasma Actuators 被引量:1
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作者 李钢 聂超群 +2 位作者 李轶明 朱俊强 徐燕骥 《Plasma Science and Technology》 SCIE EI CAS CSCD 2008年第5期605-611,共7页
Influence of plasma actuators as a flow separation control device was investigated experimentally. Hump model was used to demonstrate the effect of plasma actuators on external flow separation, while for internal flow... Influence of plasma actuators as a flow separation control device was investigated experimentally. Hump model was used to demonstrate the effect of plasma actuators on external flow separation, while for internal flow separation a set of compressor cascade was adopted. In order to investigate the modification of the flow structure by the plasma actuator, the flow field was examined non-intrusively by particle image velocimetry measurements in the hump model experiment and by a hot film probe in the compressor cascade experiment. The results showed that the plasma actuator could be effective in controlling the flow separation both over the hump and in the compressor cascade when the incoming velocity was low. As the incoming velocity increased, the plasma actuator was less effective. It is urgent to enhance the intensity of the plasma actuator for its better application. Methods to increase the intensity of plasma actuator were also studied. 展开更多
关键词 dielectric barrier discharge PLASMA separation flow control hump model compressor cascade
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FLUID FLOW SEPARATION CHARACTER ON NOVEL HYBRID JOURNAL BEARING 被引量:4
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作者 CHEN Shujiang LU Changhou LI Lei 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2006年第4期540-543,共4页
The influence of the structure and running parameters of a novel spiral oil wedge hybrid journal bearing on the fluid flow trace is investigated. The governing equation of the flow trace of lubricant is set up, and th... The influence of the structure and running parameters of a novel spiral oil wedge hybrid journal bearing on the fluid flow trace is investigated. The governing equation of the flow trace of lubricant is set up, and the simulation is carried out by using finite difference method. The results show that the lubricant flow status and end leakage quantity are greatly influenced by spiral angle,and that the rotating speed has little influence on the flow status. With advisable geometry design, the separation of lubricant between different oil wedges can be obtained, which can decrease the temperature rise effectively. 展开更多
关键词 Fluid flow separation character Spiral oil wedge flow statusHybrid journal bearing
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Flow separation control over an airfoil using continuous alternating current plasma actuator 被引量:1
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作者 Jian-Guo Zheng 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第3期346-355,共10页
The flow separation control over an NACA 0015 airfoil using continuous alternating current(AC)dielectric barrier discharge(DBD)plasma actuator is investigated experimentally and numerically.This work is intended to re... The flow separation control over an NACA 0015 airfoil using continuous alternating current(AC)dielectric barrier discharge(DBD)plasma actuator is investigated experimentally and numerically.This work is intended to report some observations made from our experiment,to which little attention is paid in the previous studies,but which is thought to be important to the understanding of control of complex flow separation with AC DBD.To this end,the response of separated flow to AC plasma actuation is visualized through the time-resolved particle image velocimetry(PIV)measurement,whereas numerical simulation is carried out to complement the experiment.The flow control process at chord-based Reynolds number(Re)of 3.31×105 is investigated.It is found that the response of external flow to plasma forcing is delayed for up to tens of milliseconds and the delay time increases with angle of attack increasing.Also observed is that at the intermediate angle of attack near stall,the forced flow features a well re-organized flow pattern.However,for airfoil at high post-stall angle of attack,the already well suppressed flow field can recover to the massively separated flow state and then reattach to airfoil surface with the flow pattern fluctuating between the two states in an irregular manner.This is contrary to one’s first thought that the forced flow at any angles of attack will become well organized and regular,and reflects the complexity of flow separation control. 展开更多
关键词 dielectric barrier discharge plasma actuator alternating current plasma discharge flow separation flow control delayed response
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Analysis and experimental study on resistance-increasing behavior of composite high efficiency autonomous inflow control device
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作者 Liang-Liang Dong Yu-Lin Zhang 《Petroleum Science》 SCIE EI CAS CSCD 2024年第2期1290-1304,共15页
Bottom water coning is the main reason to reduce the recovery of horizontal bottom water reservoir. By water coning, we mean the oil-water interface changes from a horizontal state to a mound-shaped cone and breaks th... Bottom water coning is the main reason to reduce the recovery of horizontal bottom water reservoir. By water coning, we mean the oil-water interface changes from a horizontal state to a mound-shaped cone and breaks through to the wellbore. Autonomous inflow control device(AICD) is an important instrument maintain normal production after bottom water coning, however, the resistance increasing ability of the swirl type AICD is insufficient at present, which seriously affects the water control effect. Aiming this problem, this paper designs a multi-stage resistance-increasing and composite type AICD. The separation mechanism of oil-water two phases in this structure, the resistance form of oil-water single phase and the resistance-increasing principle of water phase are analyzed. Establishing the dual-phase multi-stage separation and resistance-increasing model, and verified by measuring the throttling pressure drop and oil-water volume fraction of the AICD, it is found that the composite type AICD has the effect of ICD and AICD at the same time, which can balance the production rate of each well section at the initial stage of production, delay the occurrence of bottom water coning. In the middle and later stages of production, water-blocking can be effectively increased to achieve water control and stable production.After structural sensitivity analysis, the influence law of various structural parameters on the water control performance of composite AICD was obtained. The simulation calculation results show that,compared with the existing swirl type AICD, composite AICD has higher sensitivity to moisture content,the water phase throttling pressure drop is increased by 4.5 times on average. The composite AICD is suitable for the entire stage of horizontal well production. 展开更多
关键词 Water control flow separation flow resistance-increasing AICD device Simulation and experiment
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Fluctuating Pressure Inside/Outside the Flow Separation Region in High Speed Flowfield 被引量:1
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作者 Zhao Lei Zhao Xiaojian Li Suxun 《Journal of Aerospace Science and Technology》 2015年第1期18-26,共9页
An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside an... An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside and outside the laminar or turbulence boundary layer separation region in hypersonic flow. The changes of fluctuating pressure in separation region were focused on in this paper. The study shows that the existence of fin changes flowfiled on the plate significantly. The laminar boundary layer separation occurs earlier and the separation region is more extensive. Similar flow is observed between a couple of measurement points outside the laminar separation region. However, there are significant differences between the flow inside and outside the separation region. The level of fluctuating pressure of laminar boundary layer is smaller than that in turbulent case. Even so, in laminar case, the peak fluctuating pressure still reaches a high level. Therefore, the structural influence (damage and/or early fatigue) of fluctuating pressure loads caused by the laminar boundary layer separation should not be ignored. 展开更多
关键词 Hypersonic separated flow laminar flow blunt fin fluctuating pressure.
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Control of flow separation over a wing model with plasma synthetic jets
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作者 Zhi SU Guozheng SONG +5 位作者 Haohua ZONG Hua LIANG Jun LI Like XIE Xuecheng LIU Weiliang KONG 《Plasma Science and Technology》 SCIE EI CAS CSCD 2022年第6期135-147,共13页
An array of 30 plasma synthetic jet actuators(PSJAs)is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model.The lift and drag of the wing model are measur... An array of 30 plasma synthetic jet actuators(PSJAs)is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model.The lift and drag of the wing model are measured by a force balance,and the velocity fields over the suction surface are captured by a particle imaging velocimetry system.Results show that the flow separation of the straight wing originates from the middle of the model and expands towards the wingtips as the angle of attack increases.The flow separation can be suppressed effectively by the PSJAs array.The best flow control effect is achieved at a dimensionless discharge frequency of F^+=1,with the peak lift coefficient increased by 10.5%and the stall angle postponed by 2°.To further optimize the power consumption of the PSJAs,the influence of the density of PSJAs on the flow control effect is investigated.A threshold of the density exits(with the spanwise spacing of PSJAs being 0.2 times of the chord length in the current research),below which the flow control effect starts to deteriorate remarkably.In addition,for comparison purposes,a dielectric barrier discharge(DBD)plasma actuator is installed at the same location of the PSJAs.At the same power consumption,4.9%increase of the peak lift coefficient is achieved by DBD,while that achieved by PSJAs reaches 5.6%. 展开更多
关键词 flow separation plasma synthetic jet DENSITY dielectric barrier discharge
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Numerical study on flow separation control over NACA0015 aerofoil using electromagnetic fields
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作者 Ahmad Sedaghat Mohammad Ali Badri 《Theoretical & Applied Mechanics Letters》 CAS 2013年第5期62-68,共7页
In this study, a flow solver was developed based on the governing RANS equations of compressible flows and was further extended to include the effects of electromagnetic forces namely Lorentz forces. Lorentz forces ma... In this study, a flow solver was developed based on the governing RANS equations of compressible flows and was further extended to include the effects of electromagnetic forces namely Lorentz forces. Lorentz forces may be added as a source term in the governing fluid flow equations. Numerical studies were carried out for NACA0015 aerofoil at high angles of incidences from 15° to 30° and compared with some available cases of experimental and incompressible numerical solutions. The hydrodynamics performance was improved using a magnetic momentum coefficient of up to 0.048. The size of flow separation zone was decreased or completely eliminated by increasing this coefficient. The overall drag was not changed considerably, however the overall lift was increased up to 80 percent at stall angles. 展开更多
关键词 tromagnetic field Lorentz force flow separation NAVIER-STOKES TVD schemes
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Measurment of gas-liquid two-phase slug flow with a Venturi meter based on blind source separation
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作者 王微微 梁霄 张明柱 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2015年第9期1447-1452,共6页
We propose a novel flow measurement method for gas–liquid two-phase slug flow by using the blind source separation technique. The flow measurement model is established based on the fluctuation characteristics of diff... We propose a novel flow measurement method for gas–liquid two-phase slug flow by using the blind source separation technique. The flow measurement model is established based on the fluctuation characteristics of differential pressure(DP) signals measured from a Venturi meter. It is demonstrated that DP signals of two-phase flow are a linear mixture of DP signals of single phase fluids. The measurement model is a combination of throttle relationship and blind source separation model. In addition, we estimate the mixture matrix using the independent component analysis(ICA) technique. The mixture matrix could be described using the variances of two DP signals acquired from two Venturi meters. The validity of the proposed model was tested in the gas–liquid twophase flow loop facility. Experimental results showed that for most slug flow the relative error is within 10%.We also find that the mixture matrix is beneficial to investigate the flow mechanism of gas–liquid two-phase flow. 展开更多
关键词 Two-phase slug flow flow measurement Differential pressure Blind source separation Independent component analysis
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Comparative assessment of SAS and DES turbulence modeling for massively separated flows 被引量:4
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作者 Weilin Zheng Chao Yan +1 位作者 Hongkang Liu Dahai Luo 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第1期12-21,共10页
Numerical studies of the flow past a circular cylinder at Reynolds number 1.4 × 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation (SAS) and detached edd... Numerical studies of the flow past a circular cylinder at Reynolds number 1.4 × 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation (SAS) and detached eddy simu- lation (DES), in comparison with the existing experimental data. The new version of the model developed by Egorov and Menter is assessed, and advantages and disadvantages of the SAS simulation are analyzed in detail to provide guidance for industrial application in the future. Moreover, the mechanism of the scale-adaptive characteristics in separated regions is discussed, which is obscure in previous analyses. It is con- cluded that: the mean flow properties satisfactorily agree with the experimental results for the SAS simulation, although the prediction of the second order turbulent statistics in the near wake region is just reasonable. The SAS model can produce a larger magnitude of the turbulent kinetic energy in the recir- culation bubble, and, consequently, a smaller recirculation region and a more rapid recovery of the mean velocity out- side the recirculation region than the DES approach with the same grid resolution. The vortex shedding is slightly less irregular with the SAS model than with the DES approach, probably due to the higher dissipation of the SAS simulation under the condition of the coarse mesh. 展开更多
关键词 Scale-adaptivelength scale Bluff bodies SIMULATION von Karman Massively separated flows Computational fluid dynamics
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Applications of URANS on predicting unsteady turbulent separated flows 被引量:2
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作者 Jinglei Xu Huiyang Ma Department of Physics, Graduate University of the Chinese Academy of Sciences, 100049 Beijing, China 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2009年第3期319-324,共6页
Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2D flow past a circular cylinder at Reynolds number 3,90... Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2D flow past a circular cylinder at Reynolds number 3,900 is numerically investigated by using the technique of unsteady RANS (URANS). Some typical linear and nonlinear eddy viscosity turbulence models (LEVM and NLEVM) and a quadratic explicit algebraic stress model (EASM) are evaluated. Numerical results have shown that a high-performance cubic NLEVM, such as CLS, are superior to the others in simulating turbulent separated flows with unsteady vortex shedding. 展开更多
关键词 URANS Nonlinear eddy viscosity turbulencemodel separated flows Circular cylinder
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Numerical simulation of the pulsing air separation field based on CFD 被引量:12
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作者 He Jingfeng He Yaqun +2 位作者 Zhao Yuemin Duan Chenlong Ye Cuiling 《International Journal of Mining Science and Technology》 2012年第2期201-207,共7页
The flow field of pulsing air separation is normally in an unsteady turbulence state.With the application of the basic principles of multiphase turbulent flows,we established the dynamical computational model,which sh... The flow field of pulsing air separation is normally in an unsteady turbulence state.With the application of the basic principles of multiphase turbulent flows,we established the dynamical computational model,which shows a remarkable variation of the unstable pulsing air flow field.CFD(computational fluid dynamics) was used to conduct the numerical simulation of the actual geometric model of the classifier.The inside velocity of the flowing fields was analyzed later.The simulation results indicate that the designed structure of the active pulsing air classifier provided a favorable environment for the separation of the particles with different physical characters by density.We shot the movement behaviors of the typical tracer grains in the active pulsing flow field using a high speed dynamic camera.The displacement and velocity curves of the particles in the continuous impulse periods were then analyzed.The experimental results indicate that the effective separation by density of the particles with the same settling velocity and different ranges of the density and particle size can be achieved in the active pulsing airflow field.The experimental results provide an agreement with the simulation results. 展开更多
关键词 Pulsing air separation flow fieldMultiphase turbulence flowNumerical simulationHigh-speed dynamic camera imaging
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INVESTIGATION OF PULSED-WIRE TECHNIQUE FOR WALL PARAMETERS MEASUREMENT IN SEPARATED FLOWS
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作者 Liao Yufeng, Xu Cheng(Mechanical Engineering Institute, Nanjing University of Scienceand Technology, Nanjing, 210094, China) 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 1997年第2期98-103,共6页
A pulsed-wire wall probe measurement system was developed in this paper,which can be used for measuring wall Parameters in separated flow- The operating princi-ple was described and the way of probe calibration was gi... A pulsed-wire wall probe measurement system was developed in this paper,which can be used for measuring wall Parameters in separated flow- The operating princi-ple was described and the way of probe calibration was given. Wall parameters of back-ward-facing and forward-facing step flow were measured,and the wall nows structure andcharacters were revealed. 展开更多
关键词 separated flow MEASUREMENT pulse heating wall parameters pulsed-wire wall probe
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TURBULENT SEPARATED REATTACHED FLOW IN A TWO-DIMENSIONAL CURVED-WALL DIFFUSER
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作者 尹军飞 余少志 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1993年第2期117-123,共7页
A turbulent separation-rcattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter.The turbulent boundary layer separates on the lower curved wall... A turbulent separation-rcattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter.The turbulent boundary layer separates on the lower curved wall under strong pressure gradient and then reattaches on a parallel channel.At the inlet of the diffuser,Reynolds number based on the diffuser height is 1.2×10~5 and the velocity is 25.2m/s.The re- sults of experiments are presented and analyzed in new defined streamline-aligned coordinates.The experiment shows that after Transitory Detachment Reynolds shear stress is negative in the near-wall backflow region. Their characteristics are approximately the same as in simple turbulent shear layers near the maximum Reynolds shear stress.A scale is formed using the maximum Reynolds shear stresses.It is found that a Reynolds shear stress similarity exists from separation to reattachment and the Schofield-Perry velocity law ex- ists in the forward shear flow.Both profiles are used in the experimental work that leads to the design of a new eddy-viscosity model.The length scale is taken from that developed by Schofield and Perry.The composite velocity scale is formed by the maximum Reynolds shear stress and the Schofield Perry velocity scale as well as the edge velocity of the boundary layer.The results of these experiments are presented in this paper 展开更多
关键词 separating flow boundary layer turbulent flow turbulence model Laser Doppler Velocimeter two- dimensional diffuser
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THE EVOLUTION OF STARTING VORTEX AND SECONDARY SEPARATION ON AN ELLIPTIC CYLINDER
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作者 Zhang Dieli (Institute of Mechanics,Academia Sinica) 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1989年第1期20-30,共11页
Flow visualization was used to investigate experimentally the evolution process from symmetrical shedding to staggered shedding of the starting vortex and the phenomenon of secondary separation on an elliptic cylinder... Flow visualization was used to investigate experimentally the evolution process from symmetrical shedding to staggered shedding of the starting vortex and the phenomenon of secondary separation on an elliptic cylinder at moderate Reynolds numbers.The vortex structure of the flow separation was studied.The temporal variation of separation angle and length of wake vortex were given. The photographs and experimental results provided basis for further investigation of the complicated feature of the starting process of unsteady separated flows around an elliptic cylinder. 展开更多
关键词 unsteady separated flows starting vortex secondary vortex secondary separation staggered shedding of vortex
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Numerical Simulation and Experimental Investigation of 3 D Separated Flow Field around a Blunt Body
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作者 Doctoral Candidate: TAN Fa sheng Advisor: Prof. DAI Shi qiang Prof. WENG Pei fen (Shanghai Institute of Appllied Mathematics and Mechanics, Shanghai University) 《Advances in Manufacturing》 SCIE CAS 1999年第3期259-262,共4页
To study the effects of factors such as electromagnetic field and electron temperature on the ion extraction characteristics (extraction time, collision loss ratio) in atomic vapor laser isotope separation (AVLIS),... To study the effects of factors such as electromagnetic field and electron temperature on the ion extraction characteristics (extraction time, collision loss ratio) in atomic vapor laser isotope separation (AVLIS), 2 D electron equilibrium model was used to analyze and simulate the ion extraction process. The collisions between particles mainly considered charge exchanges between isotopic ions and atoms, which were treated by using cross section. The results show that the electric field and electron temperature have significant effects on the ion extraction characteristics: the stronger the electric field is, the higher the electron temperature is; the shorter the extraction time is, the less the collision loss ratio is, and moderate constant magnetic field has few effects on them. Key words atomic vapor laser isotope separation (AVLIS); ion extraction; charge exchange cross section; collision loss ratio 展开更多
关键词 blunt body separated flow numerical simulation NS equations flow visualization LDV experiment
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