检索结果-南通市图书馆

Statistical Analysis of Coherent Vortical Structures in a Supersonic Turbulent Boundary Layer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics Letters 2011年第3期28卷 124-127页

作者： WANG Li lu xi-yun Department of Modern Mechanics University of Science and Technology of ChinaHefei 230026

Characteristics of coherent vortical structures in a compressible turbulent boundary layer are statistically analyzed by means or airect numerical simulation of the compressible Navier-Stokes equations for Mach number M=2and Reynolds number Reθ≈1000 based on the inlet momentum *** is found that a large variety of hairpin-like and cane-like vortical structures exist in the boundary layer and the most popular structure is the cane-like *** injection and sweep events contribute a major proportion of the total Reynolds *** study indicates structural similarities with the incompressible ***,the length scales of coherent structures in the streamwise and spanwise directions increase with the distance from the *** inclination angle of vortical structures with respect to the streamwise direction increases from the suboayer to the buffer layer and then decreases from the buffer layer to the wake region.

关键词： coherent Reynolds boundary

DIRECT NUMERICAL SIMULATION OF TURBULENT HEAT TRANSFER IN A WALL-NORMAL ROTATING CHANNEL FLOW

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2006年第1期18卷 26-31页

作者： LI Bu-yang LIU Nan-sheng lu xi-yun Department of Mechanics and Mechanical Engineering University of Science and Technology of ChinaHefei 230026 China

Direct Nmerical Simulation （DNS） of turbulent heat transfer in a wall-normal rotating channel flow has been carried out for the rotation number Nr from 0 to 0.1, the Reynolds number 194 based on the friction velocity of non ro taring case and the half-height of the channel, and the Prandtl number 1. The objective of this study is to reveal the effects of rotation on the characteristics of turbulent flow and heat transfer. Based on the present calculated results, two typical rotation regimes are identified. When 0 〈 Nr 〈 0.06, turbu lence and thermal statistics correlated with the spanwise veloc ity fluctuation are enhanced since the shear rate of spanwise mean flow induced by Coriolis force increases; however, the other statistics are suppressed. When Nr 〉 0.06, turbulence and thermal statistics are suppressed significantly because the Coriolis force effect plays as a dominated role in the rotating flow. Remarkable change of the direction of near wall streak structures based on the velocity and temperature fluctuations is identified.

关键词： Direct Numerical Simulation (DNS) wallnormal rotating channel flow turbulent heat transfer thermal statistics

Interaction between strain and vorticity in compressible turbulent boundary layer

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2316-2329页

作者： CHU You Biao WANG Li lu xi yun Department of Modern Mechanics University of Science and Technology of China

The interaction of strain and vorticity in compressible turbulent boundary layers at Mach number 2.0 and 4.9 is studied by direct numerical simulation(DNS)of the compressible Navier-Stokes *** fundamental characteristics have been studied for both the enstrophy producing and destroying *** is found that large enstrophy production is associated with high dissipation and high enstrophy,while large enstrophy destruction with moderate *** enstrophy production and destruction are also correlated with the dissipation production and ***,the enstrophy producing region has a distinct tendency to be‘sheet-like’structures and the enstrophy destroying region tends to be‘tube-like’in the inner ***,the tendency to be‘sheet-like’or‘tube-like’structures is no longer obvious in the outer ***,the alignment between the vorticity vector and the strain-rate eigenvector is analyzed in the flow *** is noticed that the enstrophy production rate depends mainly on the alignment between the vorticity vector and the intermediate eigenvector in the inner layer,and the enstrophy production(destruction)mainly on the alignment between the vorticity vector and the extensive(compressive)eigenvector in the outer layer.

关键词： direct numerical simulation compressible flow turbulent boundary layer

Large-Eddy Simulation of Underexpanded Supersonic Swirling Jets

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2012年第6期29卷 196-199页

作者： WANG Guo-Lei lu xi-yun Department of Modern Mechanics University of Science and Technology of ChinaHefei 230026

A large-eddy simulation of underexpanded supersonic swirling jets issuing into a quiescent environment was carried out for two typical swirl *** corresponding nonswirling jet was also calculated for comparison and validation against the experimental *** swirling effect on the various fundamental mechanisms that dictate the intricate flow phenomena,including flow features,shock cell *** spreading characteristics and turbulence behaviors,was carefully analyzed,and it is found that the first shock cell length is reduced in the swirling jet in comparison with the nonswirling jet.A recirculation zone is formed in the high swirl number case,and the jet spreads quickly in the radial direction due to the swirling ***,intensive turbulent fluctuations are generated along the jet shear layer and at the end of the jet potential core,which will be helpful in the mixing *** obtained results provide a physical insight into understanding the mechanisms relevant to underexpanded supersonic swirling jets.

关键词： process effect expanded

NUMERICAL ANALYSIS OF THE UNSTEADY FORCE IN INSECT FORWARD FLIGHT

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2006年第2期18卷 143-147页

作者： ZHA xiong-quan lu xi-yun YIN xie-zhen Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei 230026 China

The objective of this study is to get into physical insights to the unsteady force and the relevant mechanisms in forward flight of insects. Unsteady force in the forward flight was studied, based on a virtual model problem of a foil with oscillating translation and rotation in a uniform flow, by solving the two-dimensional incompressible Navier-Stokes equations with a finite element method. The effects of typical parameters, including the advance ratio, the inclined angle of stroke plane, the stroke amplitude, and the amplitude of pitching angle of attack, on the forces and the flow structures were analyzed.

关键词： unsteady flow vortex dynamics thrust and lift,flapping motion biomechanics

TURBULENT OPEN CHANNEL FLOW SUBJECTED TO THE CONTROL OF A SPANWISE TRAVELING WAVE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第1期21卷 65-70页

作者： LIU Nan-sheng WANG Lei lu xi-yun Department of Modem Mechanics University of Science and Technology of China Hefei 230026 China

Turbulent open channel flows subjected to the control of a spanwise traveling wave have been investigated by means of Direct Numerical Simulation （DNS）. The objective of this study is to reveal the response of the near-wall and surface-influenced turbulence to the spanwise traveling wave control. Three typical frequencies of the spanwise traveling wave, i.e., high-, middle- and low-frequency, corresponding to the exciting periods at 25, 50 and 100, are considered to study the turbulence dynamics in the wall and surface regions. To elucidate the behaviors of turbulence statistics, some typical quantities, including the mean velocity, velocity fluctuations and the structures of turbulence fluctuations, are exhibited and analyzed.

关键词： turbulent open channel flow traveling wave Direct Numerical Simulation (DNS) turbulence statistics turbulence structures

ANALYSIS OF HYDRODYNAMICS FOR TWO-DIMENSIONAL FLOW AROUND WAVING PLATES

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第1期19卷 18-22页

作者： ZHANG Cheng ZHUANG Li-xian lu xi-yun Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei 230026 China

Hydrodynamic characteristics for two-dimensional flow around a waving plate are investigated. Under large Reynolds number approximation, the flow is assumed to be a combination of the outer potential flow and a thin vortex layer, which consists of a boundary layer and a shed free shear layer. A nonlinear mathematical formulation for describing the outer unsteady potential flow coupled with an unsteady boundary layer equation for the inner viscous flow adjacent to the waving plate is developed. A semi-analytical method with a nonlinear Kutta condition imposed at the trailing edge is used to solve the velocity field of the outer flow and the evolution of wake vortex induced by a large-amplitude waving plate. The unsteady boundary layer equation is solved by extending Pohlhausen＇s method to its unsteady counterpart. The thrust and viscous drag coefficients, propulsive efficiency, and the pattern of wake vortex sheet are discussed.

关键词： waving plate fish swimming unsteadyboundary layer vortex shedding

Flutter of Finite-Span Flexible Plates in Uniform Flow

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2010年第6期27卷 126-128页

作者： BAO Chun-Yu TANG Chao YIN xie-Zhen lu xi-yun Department of Modern Mechanics University of Science and Technology of China Hefei 230027

The flutter instability and response of finite-span flexible plates in uniform flow are investigated experimentally. The effects of the plate aspect ratio on its dynamic responses are mainly analyzed. A hysteretic phenomenon is observed and can be described such that the plate flutters spontaneously as the flow velocity is greater than a critical value UC and the plate returns to its stable state as the flow velocity is slowly decreased to another critical one UD. We find that the aspect ratio has a greater effect on UC than on UD. The flutter frequency decreases and the amplitude increases with the increase in the flow velocity. When the flutter instability of the plate occurs, three typical flutter modes are identified and are associated with the aspect ratio and the flow velocity.

关键词： FluTTER (Aerodynamics) PLATES (Engineering) AERODYNAMICS HYSTERESIS FluID dynamics

FINITE ELEMENT ANALYSIS OF LAMINAR FLOW AND HEAT TRANSFER IN A BUNDLE OF CYLINDERS

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2000年第4期12卷 99-108页

作者： Wang Yan-xing Zhao Hong lu xi-yun Zhuang Li-xian Department of Modern Mechanics University of Science and Technology of ChinaHefeiAnhui 230026P.R.China

Two-dimensional Navier-Stokes equations and energy equation governing incompressible laminar flow past a bundle of cylinders were numerically solved by using the finite element method. The velocity correction method was used for time advancement, and spatial discretization was carried out with the Galerkin weighted residual method. Viscous flows past the cylinder banks arranged in in-line cylinder bundles and staggered cylinder bundles, coupled with heat transfer, were investigated for pitch-diameter ratios of 1.5 and 2.0 and the Reynolds numbers from 50 to 500. Flow structures and heat transfer behavior were discussed. The results obtained agree well with available numerical data.

关键词： finite element method velocity correction method heat transfer bundle of cylinders