AN INTEGRATEDC METHOD FOR COMPUTING COMPUTING THE INTERNAL AND EXTERNAL VISCOUS FLOW FIELD AROUND THE DUCTED PROPULSOR BEHIND AN AXISYMMETRIC BODY

ＡＮＩＮＴＥＧＲＡＴＥＤＣＭＥＴＨＯＤＦＯＲＣＯＭＰＵＴＩＮＧＣＯＭＰＵＴＩＮＧＴＨＥＩＮＴＥＲＮＡＬＡＮＤＥＸＴＥＲＮＡＬＶＩＳＣＯＵＳＦＬＯＷＦＩＥＬＤＡＲＯＵＮＤＴＨＥＤＵＣＴＥＤＰＲＯＰＵＬＳＯＲＢＥＨＩＮＤＡＮＡＸＩＳＹＭＭＥＴＲＩＣＢＯＤ...     

NUMERICAL SIMULATION AND EXPERIMENTAL STUDY OF THE FLOW FIELD AROUND A CIRCULAR CYLINDRICAL ARTIFICIAL ISLAND UNDER THE ACTION OF WAVES AND VISCOUS CURRENT

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＡＮＤＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＯＦＴＨＥＦＬＯＷＦＩＥＬＤＡＲＯＵＮＤＡＣＩＲＣＵＬＡＲＣＹＬＩＮＤＲＩＣＡＬＡＲＴＩＦＩＣＩＡＬＩＳＬＡＮＤＵＮＤＥＲＴＨＥＡＣＴＩＯＮＯＦＷＡＶＥＳＡＮＤＶＩＳＣＯＵ...     

NUMERICAL SIMULATION OF THE EFFECT OF FILLET FORMS ON APPENDAGE－BODY JUNCTION FLOW

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＴＨＥＥＦＦＥＣＴＯＦＦＩＬＬＥＴＦＯＲＭＳＯＮＡＰＰＥＮＤＡＧＥ－ＢＯＤＹＪＵＮＣＴＩＯＮＦＬＯＷＬｉＤｉｎｇ；ＺｈｏｕＬｉａｎ－ｄｉ（ＣｈｉｎａＳｈｉｐＳｃｉｅｎｔｉｆｉｃＲｅｓｅａｒｃｈＣｅｎｔｅｒＰ．...     

A NEW APPROACH TO THE SIMULATION OF UNSTEADY SUBCRITICAL FLOW

ＡＮＥＷＡＰＰＲＯＡＣＨＴＯＴＨＥＳＩＭＵＬＡＴＩＯＮＯＦＵＮＳＴＥＡＤＹＳＵＢＣＲＩＴＩＣＡＬＦＬＯＷ￥ＭａｏＺｅ－ｙｕ（ＤｅｐａｒｔｍｅｎｔｏｆＨｙｄｒａｕｌｉｃＥｎｇｉｎｅｅｒｉｎｇ，ＴｓｉｎｇｈｕａＵｎｉｖｅｒｓｉｔｙＢｅｉｊｉｎｇ１０００８...     

NATURAL CONVECTIVE HEAT AND MASS TRANSFER BY THE COUPLING OF TEMPERATURE CRADIENT AND CONCENTRATION GRADIENT IN A POROUS MEDIUM

ＮＡＴＵＲＡＬＣＯＮＶＥＣＴＩＶＥＨＥＡＴＡＮＤＭＡＳＳＴＲＡＮＳＦＥＲＢＹＴＨＥＣＯＵＰＬＩＮＧＯＦＴＥＭＰＥＲＡＴＵＲＥＣＲＡＤＩＥＮＴ　ＡＮＤＣＯＮＣＥＮＴＲＡＴＩＯＮＧＲＡＤＩＥＮＴＩＮＡＰＯＲＯＵＳＭＥＤＩＵＭ￥ＣｈｅｎＢａＯ－Ｍｉｎｇ；Ｆ...     

NUMERICAL SIMULATION OF THE TURBULENT FLUID FLOW AND PREDICTION OF INCIPIENT CAVITATION NUMBER ON ISOLATED SURFACE TRIANGULAR PROTRUSION

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＴＨＥＴＵＲＢＵＬＥＮＴＦＬＵＩＤＦＬＯＷＡＮＤＰＲＥＤＩＣＴＩＯＮＯＦＩＮＣＩＰＩＥＮＴＣＡＶＩＴＡＴＩＯＮＮＵＭＢＥＲＯＮＩＳＯＬＡＴＥＤＳＵＲＦＡＣＥＴＲＩＡＮＧＵＬＡＲＰＲＯＴＲＵＳＩＯＮ￥ＲｅｎＢｉ...     

NUMERICAL COMPUTATION OF THE DIFFUSION OF THE CONTAMINANTS AND THE FLOW FIELD OF SKEW DISCHARGES INTO A CHANNEL

ＮＵＭＥＲＩＣＡＬ　ＣＯＭＰＵＴＡＴＩＯＮ　ＯＦ　ＴＨＥ　ＤＩＦＦＵＳＩＯＮ　ＯＦ　ＴＨＥ　ＣＯＮＴＡＭＩＮＡＮＴＳ　ＡＮＤ　ＴＨＥ　ＦＬＯＷ　ＦＩＥＬＤ　ＯＦ　ＳＫＥＷ　ＤＩＳＣＨＡＲＧＥＳ　ＩＮＴＯ　Ａ　ＣＨＡＮＮＥＬＮＵＭＥＲＩＣＡＬＣＯＭＰＵ...     

THE INFLUENCE OF THE SECONDARY NORMAL STRESS DIFFERENCE OF VISCOELASTIC FLUID ON ECCENTRIC CAPSULE FLOW

ＴＨＥＩＮＦＬＵＥＮＣＥＯＦＴＨＥＳＥＣＯＮＤＡＲＹＮＯＲＭＡＬＳＴＲＥＳＳＤＩＦＦＥＲＥＮＣＥＯＦＶＩＳＣＯＥＬＡＳＴＩＣＦＬＵＩＤＯＮＥＣＣＥＮＴＲＩＣＣＡＰＳＵＬＥＦＬＯＷ￥ＰａｎＤａ－ｌｉｎ（ＧｕａｎｇｄｏｎｇＩｎｓｔｉｔｕｔｅｏｆｏｆＴｅｃ...     

THE APPLICATION OF THE AVERAGING FINITE DIFFERENCE SCHEME IN THE SIMULATION OF SEPARATED FLOW

ＴＨＥ　ＡＰＰＬＩＣＡＴＩＯＮ　ＯＦ　ＴＨＥ　ＡＶＥＲＡＧＩＮＧ　ＦＩＮＩＴＥ　ＤＩＦＦＥＲＥＮＣＥ　ＳＣＨＥＭＥ　ＩＮ　ＴＨＥ　ＳＩＭＵＬＡＴＩＯＮ　ＯＦ　ＳＥＰＡＲＡＴＥＤ　ＦＬＯＷＴＨＥＡＰＰＬＩＣＡＴＩＯＮＯＦＴＨＥＡＶＥＲＡＧＩＮＧＦＩＮＩ...     

STUDY ON THE MECHANISM OF TURBULENT PRODUCTION AND BURST DETECTION OVER A ROUGH WALL

ＳＴＵＤＹＯＮＴＨＥＭＥＣＨＡＮＩＳＭＯＦＴＵＲＢＵＬＥＮＴＰＲＯＤＵＣＴＩＯＮＡＮＤＢＵＲＳＴＤＥＴＥＣＴＩＯＮＯＶＥＲＡＲＯＵＧＨＷＡＬＬ￥ＷａｎｇＪｉｎ－Ｊｕｎ（ＩｎｓｔｉｔｕｔｅｏｆｆｌｕｉｄＭｅｃｈａｎｉｃｓ，ＢｅｉｊｉｎｇＵｎｉｖｅｒｓｉ...     

各向异性对无切变边界层与轴对称应变湍流特性的影响

本文运用湍流快速畸变理论对各向异性条件对无切变边界层及轴对称应变湍流特性的影响进行了探讨，对无切变边界层，所进行扮析与实验资料表明，此时各向异性的影响在于增加纵向紊动强度及减小横向紊动强度，但其对垂向紊动影响甚小，对轴对称应变湍流，本文也对紊动强度与雷诺应力随向各异性条件的变化进行了分析。     

Turbulent flow structure at a 90-degree open channel confluence: Accounting for the distortion of the shear layer

City channels often have a smaller width-to-depth ratio in comparison to natural rivers due to the limited land availability. The penetration of the tributary into the main channel can cause the distortion of the shear layer. The main purpose of the present study is to investigate the mean and turbulent flow structure in the distorted shear layer in a discharge-adjustable plexiglass circulating flume. Three-dimensional velocities were collected and hydrodynamics and turbulence characteristics such as mean velocity field, turbulent kinetic energy, Reynolds shear stress, turbulence spectrum, and occurrence probabilities of quadrant events were analyzed. The results showed that a stronger helical cell was formed and extended for a longer distance downstream when the tributary channel had a higher flow rate than the main channel. The maximum Reynolds shear stress and the ejection and sweep events were mainly distributed at the middle zone of the water depth, rather than near the water surface, which were coincident with the shear layer as indicated by the turbulence kinetic energy. No obvious energy concentration was observed, and the power law relations for individual velocity components all had an exponent slightly larger than −5/3 in the flow frequency. The distortion of the shear layer resulted in an increase in occurrence probabilities of ejection and sweep events within the shear layer, which were related to the turbulence presenting vortices induced by wall. If the discharge ratio remained unchanged, an increase in the discharge of both channels resulted in an increase in some parameters, such as velocity, turbulent kinetic energy, and the absolute values of Reynolds shear stress, while the shear layer was distorted to a larger extent as the discharge of each channel decreased. All these results suggested that sediment transport, bed morphology and contaminant transport in the distorted shear layer at city channel confluences may differ significantly from that at natural river confluences.     

EFFECT OF NON-SPHERICAL PARTICLES ON THE FLUID TURBULENCE IN A PARTICULATE PIPE FLOW

In the non-spherical particulate turbulent flows,a set of new fluid fluctuating velocity equations with the nonspherical particle source term were derived, then a new method,which treats the slowly varying functions and rapidly varying functions separately, was proposed to solve the equations, and finally the turbulent intensity and the Reynolds stress of the fluid were obtained by calculating the fluctuating velocity statistically. The equations and method were used to a particulate turbulent pipe flow. The results show that the turbulent intensity and the Reynolds stress are decreased almost inverse proportionally to the fluctuating velocity ratio of particle to fluid. Nonspherical particles have a greater suppressing effect on the turbulence than the spherical particles. The particles with short relaxation time reduce the turbulence intensity of fluid, while the particles with long relaxation time increase the turbulence intensity of fluid. For fixed particle and fluid, the small particles suppress the turbulence and the large particles increase the turbulence.     

THEORETICAL ANALYSIS AND NUMERICAL SIMULATION OF TURBULENT FLOW AROUND SAND WAVES AND SAND BARS

Natural rivers usually possess sand waves and sand bars. In this article, the rapid distortion theory was used to study the turbulent flow over sand waves. The results show that the pre-existing shearing motion and upstream anisotropy of the turbulence flow would have significant effect on the turbulent structures, and hence the memory effect should be taken into consideration. Furthermore, the 2-D mathematical model was employed to simulate the unsteady flow around the Taiping Sand Bar in the lower reach of the Yangtze River and the time step effect on the unsteady flow simulation with the implicit scheme was discussed at the same time. The results show that the implicit scheme keeps effective until the time step reaches a certain number, and the calculated water levels and velocities are in agreement with the observed data.     

二维自由剪切湍流的实验结果及其与理论计算的比较

本文用热线风速仪和数据采样技术,对二维湍流混合层、湍尾流和湍射流自模拟区内的平均速度、湍流强度、雷诺应力和脉动速度的高阶关联进行了测量,所得结果与不可压缩流体剪切湍流理论的计算结果进行了比较,两者吻合得较好。     

A STUDY ON NUMERICAL METHOD OF NAVIER-STOKES EQUATION AND NON-LINEAR EVOLUTION OF THE COHERENT STRUCTURES IN A LAMINAR BOUNDARY LAYER

1. INTRODUCTION A high accuracy compact finite difference scheme has been extensively applied to direct simulation of turbulence coherent structure’s complicated and remote physical phenomena [1-5]. The Fourier spectralexpansion was previously commonly …     

开孔促淤板周围水流紊动特性试验研究

为深入了解开孔促淤板周围的水流特性,通过室内概化水槽试验分析了开孔促淤板前后的水流紊动特性,采用声学多普勒流速仪(ADV)测量了开孔促淤板前后典型断面上的三维瞬时流速,分析了典型断面上的时均流速、紊动强度、雷诺切应力和紊动能的分布规律。试验结果表明:板后近板区出现回流区,且回流区与开孔促淤板格栅位置相对应;板后水流相对紊动强度、雷诺切应力及相对紊动能明显大于板前,开孔促淤板对板后近板区水流影响较大;随着与开孔促淤板距离的增大,回流现象消失,流速变化趋于稳定,水流相对紊动强度减小且最终趋于稳定,相对紊动能出现折减且折减率逐渐降低;靠近近板区xOy面雷诺切应力大于yOz面雷诺切应力,靠近下游xOy面雷诺切应力与yOz面雷诺切应力相差较小。     

EXPERIMENTAL STUDY OF FLOW STRUCTURE BEHIND A CIRCULAR CYLINDER WITH WAVY SURFACE BY PIV

1. INTRODUCTIONThe flow around a s mooth circular cylinderhas been extensively studied by many researchers ,as can be seen fromthe comprehensive reviews ofWilliamson[1]and Rockwell[2]. Wang et al .[3]in-vestigated the 3D flow structure behind a circularcy…     

The mechanical energy equation for total flow in open channels

The mechanical energy equation is a fundamental equation of a 1-D mathematical model in Hydraulics and Engineering Fluid Mechanics. This equation for the total flow used to be deduced by extending the Bernoulli＇s equation for the ideal fluid in the streamline to a stream tube, and then revised by considering the viscous effect and integrated on the cross section. This derivation is not rigorous and the effect of turbulence is not considered. In this paper, the energy equation for the total flow is derived by using the Navier-Stokes equations in Fluid Mechanics, the results are as follows：（1） A new energy equation for steady channel flows of incompressible homogeneous liquid is obtained, which includes the variation of the turbulent kinetic energy along the channel, the formula for the mechanical energy loss of the total flow can be determined directly in the deduction process.（2） The theoretical solution of the velocity field for laminar flows in a rectangular open channel is obtained and the mechanical energy loss in the energy equation is calculated. The variations of the coefficient of the mechanical energy loss against the Reynolds number and the width-depth ratio are obtained.（3） The turbulent flow in a rectangular open channel is simulated using 3-D Reynolds averaged equations closed by the Reynolds stress model（RSM）, and the variations of the coefficient of the mechanical energy loss against the Reynolds number and the width-depth ratio are discussed.     

Bottom shear stress in unsteady sewer flow.

The properties of unsteady open-channel turbulent flow were theoretically and experimentally investigated in a circular cross section channel with fixed sediment deposits. Velocity and turbulence distribution data were obtained using an ultrasonic velocity profiler (UVP). Different uniform flow conditions and triangular-shaped hydrographs were analysed. The hydrograph analysis revealed a dynamic wave behaviour, where the time lags of mean cross section velocity, friction velocity, discharge and flow depth were all evident. The bottom shear stress dynamic behaviour was estimated using four different approaches. Measurements of the velocity distribution in the inner region of the turbulent layer and of the Reynolds stress distribution in the turbulent flow provided the analysed data sets of the bottom shear stress. Furthermore, based on the Saint Venant equation, the bottom shear stress time behaviour was studied using both the kinematic and the dynamic flow principles. The dynamic values of the bottom shear stress were compared with those for the steady flow conditions. It is evident that bottom shear stress varies along the generated flood hydrograph and its variation is the function of the flow unsteadiness. Moreover, the kinematic flow principle is not an adequate type of approximation for presented flow conditions.