矩形明渠边界平均剪切应力变化规律研究

针对棱柱型矩形明渠的特点 ,在分析均匀流运动机理的基础上 ,认为水流可以分为河床作用部分和岸壁作用部分 ,各部分分别作均匀流运动。在分析水体能量消耗的物理模式的基础上 ,提出了面积分割的补充关系。对于河床和岸壁糙率相同的情况 ,利用静力平衡条件和水流连续方程 ,可推得水流槽底、岸壁剪应力的计算关系式。对关系式的讨论表明 ,公式结构合理 ,能反映明渠水流的特点。对已有水槽试验资料进行的分析表明本文提出的计算关系式较好地描述水流的实际情况 ,比已有的公式更简便可靠。     

STUDY OF NONLINEAR LONG WAVE APPOXIMATION IN UNIFORM CHANNELS VIA HAMILTONIAN STRUCTURE

ＳＴＵＤＹＯＦＮＯＮＬＩＮＥＡＲＬＯＮＧＷＡＶＥＡＰＰＯＸＩＭＡＴＩＯＮＩＮＵＮＩＦＯＲＭＣＨＡＮＮＥＬＳＶＩＡＨＡＭＩＬＴＯＮＩＡＮＳＴＲＵＣＴＵＲＥ￥ＸｕＸｉｎ－ｓｈｅｎｇ；ＺｈｏｎｇＷａｎ－ｘｉｅ；ＬｕＹｕ－ｌｉｎ（ＩｎｓｔｉｔｕｔｅｏｆＥｎｇ...     

2-D CHARACTERISTICS-LIKE MODEL AND OPEN BOUNDARY CONDITION FOR UNSTEADY OPEN CHANNEL FLOW MODELING

1.　ＩＮＴＲＯＤＵＣＴＩＯＮＵｎｓｔｅａｄｙｏｐｅｎｃｈａｎｎｅｌｆｌｏｗｓｗｉｔｈｒａｐｉｄｃｈａｎｇｅｏｆｗａｔｅｒｌｅｖｅｌｏｆｔｅｎｏｃｃｕｒｓｉｎｔｈｅｍａｎｍａｄｅｃｈａｎｎｅｌｓａｎｄｎａｔｕｒａｌｒｉｖｅｒｓ.Ｔｈｅｄａｍｂｒｅａｋｆ?..     

THRESHOLD CONDITION FOR CHOCKING IN OPEN CHANNELS AND EXCAVATION OF TAILRACE

On the basis of energy and continuity equations a general threshold condition for chocking in open channels is obtained and a representation in terms of the Froude number at the upstream section and other parameters is given to predict whether the chocking phenomenon occurs or not at the downstream section. From the general threshold condition for chocking the limit contraction ratios of the channel width are introduced for both with and without the energy losses and a criterion for excavation of the tailrace to avoid chocking is derived. An example shows that using these criterion and the representation proposed for calculating flow depth it is very easy to determine the scheme of the excavation of the open channels.     

MIXING MODEL EXTENDED TO TURBULENT FLOW IN NARROW SMOOTH OPEN CHANNELS

ＭＩＸＩＮＧＭＯＤＥＬＥＸＴＥＮＤＥＤＴＯＴＵＲＢＵＬＥＮＴＦＬＯＷＩＮＮＡＲＲＯＷＳＭＯＯＴＨＯＰＥＮＣＨＡＮＮＥＬＳＮｉＪｉｎ－ｒｅｎ（ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｇｒａｐｈｙ，ＰｅｋｉｎｇＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉｊｉｎｇ１００８７１，Ｐ．...     

THE TURBULENCE CHARACTERISITICS OF OPEN CHANNEL FLOW

ＴＨＥ　ＴＵＲＢＵＬＥＮＣＥ　ＣＨＡＲＡＣＴＥＲＩＳＩＴＩＣＳ　ＯＦ　ＯＰＥＮ　ＣＨＡＮＮＥＬ　ＦＬＯＷＴＨＥＴＵＲＢＵＬＥＮＣＥＣＨＡＲＡＣＴＥＲＩＳＩＴＩＣＳＯＦＯＰＥＮＣＨＡＮＮＥＬＦＬＯＷ￥ＷａｎｇＸｉｎｇ－ｋｕｉ（Ｄｅｐａｒｔ．ｏｆＨｙｄｒ...     

FINITE-VOLUME TVD ALGORITHM FOR DAM-BREAK FLOWS IN OPEN CHANNELS

1 .　INTRODUCTIONThepropagationofborewavesorthemove mentoffreesurfaceflowscausedbydambreak ing ,orsuddenopeningorclosingofasluiceinachannelhasincreasedinterestinenvironmentalandhydraulicengineering .Generallyitcanbede scribedbytheShallowWaterEquations (SWE )throughtheintegrationoftheNavier Stokesequationsoverdepthwiththeassumptionsofhydrostaticpressuredistributionandmildchannel bedslope .ManyclassicaltechniquesthatwereusedforsolvingtheSWEcanbefoundinthepaststudies .However ,whendiscon…     

VELOCITY DISTRIBUTIONS OF SUSPENDED SEDIMENT-LADEN FLOWS IN OPEN CHANNELS

This paper presents an analysis on the velocity distributions of steady,uniform suspended sediment-laden flows in open channels.The sediment particle-particle interactions and the buoyancy effects due to density stratification are taken into account respectively through the water-sediment mixture's constitutive relationship and an adapted Monin-Obukhov lengthscale to validate the theory for a wider spectrum of sediment concentrations.The developed model,with the same yon Karman coefficient as that of a single phase flow,is shown to be in excellent agreement with measurements of controlled experiments with both low and heavy sediment concentrations.     

2－D SIMULATION OF OPEN CHANNEL TURBULENT FLOW WITH HIGH REYNOLDS NUMBER BY EMPLOYING N－S EQUATIONS AND IEM

２－ＤＳＩＭＵＬＡＴＩＯＮＯＦＯＰＥＮＣＨＡＮＮＥＬＴＵＲＢＵＬＥＮＴＦＬＯＷＷＩＴＨＨＩＧＨＲＥＹＮＯＬＤＳＮＵＭＢＥＲＢＹＥＭＰＬＯＹＩＮＧＮ－ＳＥＱＵＡＴＩＯＮＳＡＮＤＩＥＭ￥ＷａｎｇＤｉｎｇ－ｙａｎｇ；ＬｉｕＨｅ－ｄｏｎｇ（ＹａｎｇｔｚｅＲｉ...     

VELOCITY DISTRIBUTION IN TRAPEZOID-SECTION OPEN CHANNEL FLOW WITH A NEW REYNOLDS-STRESS EXPRESSION

By considering that the coherent structure is the main cause of the Reynolds stress, a new Reynolds stress expression was given. On this basis the velocity distribution in the trapezoid-section open channel flow was worked out with the pseudo-spectral method. The results were compared with experimental data and the influence of the ratio of length to width of the cross-section and the lateral inclination on the velocity distribution was analyzed. This model can be used the large flux in rivers and open channes.     

A NEW MEASURE FOR DIRECT MEASUREMENT OF THE BED SHEAR STRESS OF WAVE BOUNDARY LAYER IN WAVE FLUME

In this article, a shear plate was mounted on the bottom in a wave flume and direct measurements of the smooth and rough bed shear stress under regular and irregular waves were conducted with the horizontal force exerted on the shear plates by the bottom shear stress in the wave boundary layer. Under immobile bed condition, grains of sand were glued uniformly and tightly onto the shear plate, being prevented from motion with the fluid flow and generation of sand ripples. The distribution of the bottom mean shear stress varying with time was measured by examining the interaction between the shear plate and shear transducers. The relation between the force measured by the shear transducers and its voltage is a linear one. Simultaneous measurements of the bottom velocity were carried out by an Acoustic Doppler Velocimeter (ADV), while the whole process was completely controlled by computers, bottom shear stress and velocity were synchronously measured. Based on the experimental results, it can be concluded that (1) the friction coefficient groews considerably with the increase of the Reynolds number, (2) the shear stress is a function varying with time and linearly proportional to the velocity. Compared with theoretical results and previous experimental data, it is shown that the experimental method is feasible and effective, A further study on the bed shear stress under regular or irregular waves can be carried out. And applicability to the laboratory studies on the initiation of sediments and the measurement of the shear stress after sediment imigration.     

THREE-DIMENSIONAL LARGE EDDY SIMULATION OF FREE SURFACE TURBULENT FLOW IN OPEN CHANNEL WITHIN SUBMERGED VEGETATION DOMAIN

1 .　INTRODUCTIONInactualrivers ,theriverbediscommonlycoveredbyvegetation .Thevegetationinriversplaysanimportantroleontheenvironmentalfunc tionoftherivers,thatis,theamenitytohumanlife ,livingspaceformanylives ,purificationofwaterqualityandsoon .However ,thevegetationinriversalsoplaysakeyroleonthecarryingca pacityofachannelwithfloodplains .Therefore ,thehydraulicsoftheflowwithvegetationshouldbemoreimprovedorrefined .Logicalexplanationandaccurateevaluationaboutturbulentflowinopenchannelwith…     

ANALYSIS OF PULSATILE FLOW IN THE PARALLEL-PLATE FLOW CHAMBER WITH SPATIAL SHEAR STRESS GRADIENT

The Parallel-Plate Flow Chamber (PPFC), of which the height is far smaller than its own length and width, is one of the main apparatus for the in-vitro study of the mechanical behavior of cultured vascular Endothelical Cells (ECs) exposed to fluid shear stress. The steady flow in different kinds of PPFC has been extensively investigated, whereas, the pulsatile flow in the PPFC has received little attention. In consideration of the characteristics of geometrical size and pulsatile flow in the PPFC, the 3-D pulsatile flow was decomposed into a 2-D pulsatile flow in the vertical plane, and an incompressible plane potential flow in the horizontal plane. A simple method was then proposed to analyze the pulsatile flow in the PPFC with spatial shear stress gradient. On the basis of the method, the pulsatile fluid shear stresses in several reported PPFCs with spatial shear stress gradients were calculated. The results were theoretically meaningful for applying the PPFCs in-vitro, to simulate the pulsatile fluid shear stress environment, to which cultured ECs were exposed.     

THE LARGE EDDY SIMULATION OF STRONGLY CURVED OPEN CHANNEL FLOW

ＴＨＥＬＡＲＧＥＥＤＤＹＳＩＭＵＬＡＴＩＯＮＯＦＳＴＲＯＮＧＬＹＣＵＲＶＥＤＯＰＥＮＣＨＡＮＮＥＬＦＬＯＷ￥ＺｈｏｕＦａ－ｙｉ（Ｄｅｐｔ．ｏｆＣｉｖｉｌＥｎｇｒｇ．，ＤａｌｉａｎＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ，Ｄａｌｉａｎ１１６０２３，...     

EXPERIMENTAL INVESTIGATION ON SOUND SPEED PROPAGATING THROUGH HIGH SPEED AERATED FLOW IN OPEN CHANNEL

An experiment concerning the sound propaga-tion in aerated open channel flow was designed and conductedin a variable slope chute. The acquisition of sound data wasdone by the hydro-phones installed into the bottom wall of thechute. The data were analyzed and processed by the tape re-corder and a 3562A analyzer. The primary experimetal resultsindicated that the sound speed in aerated flow is varied with the air concentration and highly lower than each of the soundspeed in pure water or air. As released by the derived theoryformula, the minimum sound of 24m/s in aerated flow hap-pened when the air concentration achieved to 50%. This resultshows that the compressibility of high speed aerated flowshould be considered when the air concentration is near to50%. A criterion of compressibility of high speed aerated flowwas also giv. En in this paper.     

矩形明渠均匀流水深和底宽的算子分裂算法式

   应用算子分裂思想将矩形明渠均匀流方程分裂为两个简单算式,通过耦合方法建立了整个定义域内的统一近似算式,该算式结构简明,计算方便,精度可达10-5。     

LARGE EDDY SIMULATION OF PULSATING TURBULENT OPEN CHANNEL FLOW

Pulsating turbulent open channel flow has been investigated by the u.se of I.arge Eddy Simulation (I.ES) technique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulent SGS stress to closure the governing equations.Three-dimensional filtered Navier-Stokes equations are numerically solved by a fractional-- step method. The objective of this study is to deal with the behavior of the pulsating turbulent open channel flow and to examine the reliability of the I.ES approach for predicting the pulsating turbulent flow. In this study, the Reynolds number (Re,) is chosen as 180 based on the friction velocity and the channel depth, The frequency of the driving pressure gradient for the pulsating turbulent flow ranges low, medium and high value, Statistical turbulence quantities as well as the flow structures are analyzed.     

A NON LINEAR ANALYSIS OF TWO PHASE FLOW INSTA BILITY IN PARALLEL CHANNELS OF A BOILING SYSTEM

１．　ＩＮＴＲＯＤＵＣＴＩＯＮＴｗｏｐｈａｓｅｆｌｏｗｉｎｓｔａｂｉｌｉｔｙａｒｅｏｆｔｅｎｅｎｃｏｕｎｔｅｒｅｄｉｎａｗｉｄｅｒａｎｇｅｏｆｅｎｇｉｎｅｅｒｉｎｇｓｙｓｔｅｍｓ，ｓｕｃｈａｓｎｕｃｌｅａｒｒｅａｃｔｏｒｓ，ｓｔｅａｍｐｏｗｅｒｐｌａｎｔｓ，ｓｐｅｃｉａｌｈｅａｔｅｘｃｈａｎｇｅｒｓ，ｓｔｅａｍｇｅｎｅｒａｔｏｒｓ，ｃｈｅｍｉｃａｌｉｎｄｕｓｔｒｙｅｑｕｉｐｍｅｎｔｓａｎｄｓｏｏｎ［１］［２］　．Ｉｎｔｈｅｓｅｓｙｓｔｅｍｓ，ｔｗｏｐｈａｓｅｆｌｏｗｉｎｓｔａｂｉｌｉｔ…     

Numerical investigation of flow through vegetated multi-stage compound channel

This paper addresses the problem of the renormalization group k turbulence modeling of a vegetated multi-stage compound channel. Results from Micro acoustic Doppler velocimeter（ADV） tests are used with time and spatial averaging（doubleaveraging method） in the analysis of the flow field and the characterization. Comparisons of the mean velocity, the Reynolds stress, and the turbulent energy distribution show the validity of the computational method. The mean velocity profile sees an obvious deceleration in the terraces because of vegetation. Secondary flow exists mainly at the junction of the main channel and the vegetation region on the first terrace. The bed shear stress in the main channel is much greater than that in the terraces. The difference of the bed shear stress between two terraces is insignificant, and the presence of vegetation can effectively reduce the bed shear stress.     

QUADRANT ANALYSIS OF BUBBLE INDUCED VELOCITY FLUCTUATIONS IN A TRANSITIONAL BOUNDARY LAYER

Our previous study showed that the frictional drag decreases with increasing void fraction at Re > 1300, while it increases at Re < 1000. Decomposition of the Reynolds shear stress also implied that bubbles induce isotropy of turbulence. In order to confirm our previous analysis and to further investigate flow fields in the vicinity of bubbles, we analyze velocity fluctuations on the quadrant space in the streamwise and transverse directions ( u′ – v′ plane). Here, we focus on two specific Reynolds numbers ...