ADV技术测量圆射流流场紊动特性实验

利用 ADV(Acoustic Doppler Velocimeter)技术对静止环境条件下圆射流流场紊动特性进行了研究 .通过专门的 Win ADV系统分析软件获得了射流横断面上流速的紊动强度、偏斜度、平坦度及雷诺应力的分布 ,轴线流速紊动强度的变化和射流瞬时速度变化等紊动特性 ,并将所得成果与已有的国内外成果进行了比较     

ADV技术测量圆射流流场紊动特性实验

利用ＡＤＶ（Ａｃｏｕｓｔｉｃ Ｄｏｐｐｌｅｒ Ｖｅｌｏｃｉｍｅｔｅｒ）技术对静止条件下圆射流流场紊动特性进行了研究。通过专门的ＷｉｎＡＤＶ系统分析软件获得了射流横断面上流速的紊动强度，偏斜度、平坦度及雷诺应力的分析，轴线流速紊动强度的变化和射流瞬时速度变化等紊动特性，并将所得成果与已有的国内外成果进行了比较。     

ADV在波浪边界层流动特性研究中的应用

本文介绍新声学多普勒流速仪（Acoustic-Doppler Velocimeter）技术在波浪流动特性研究中的应用。通过波浪水槽试验,利用ADV测量椭圆余弦波作用下不同底床情况,垂线上各点的瞬时流速。将瞬时流速进行相位平均,计算了各点的紊动强度。试验结果显示：在平底床面,水平流速u沿水深变化曲线体现了椭圆余弦波流速的不对称性;分析紊动强度沿水深分布,两种床面上水平流速u的紊动强度明显大于另外两个方向,沙纹床面上由于受到分离涡的影响,紊动强度沿水深分布和平坦床面上的特性有较大不同。     

流动环境中高浓度射流的三维数值模拟

应用流动环境中高浓度圆孔射流的三维RNG湍流模型,模拟计算不同水深和环境来流下的流态和浓度场分布,结果表明在已有射流区、冲击区以及异重流区的基础上,还存在1个上游入侵区。该上游入侵区的长度随环境流速的增大而减小,水深对其的影响相对较小。射流触底点位置随环境流速以及水深的增大而下移,触底点浓度则随环境流速以及水深的增大而减小。流态分析显示,壁面反射流形成动量较强的附壁射流时,会在较短距离内收缩和膨胀,紊动掺混剧烈,水深较浅时容易形成全水深掺混。比较而言,附壁射流较弱时无上游入侵,在射流孔口下游附近横断面上会形成较为特别的水滴状浓度等值线分布,在水体底部形成更为稳定的异重流。最后探讨了水体底面横向最大浓度沿流向的分布特征。     

高含沙水流运动特性综述

本文综述了高含沙水流的阻力特征，流速分布，紊动强度分布，能量分布等流动过程中所具有的特性，并和清水、低含沙水流作了对比分析，系统论述高，低含沙水流所共同具有的规律。     

泥沙对挟沙水流流动结构影响的研究

应用MicroADV研究了不同粒径的泥沙颗粒在不同水力条件下对水流流动结构的影响。实验发现：挟沙水流流动结构的变化不仅与颗粒的大小密切相关，而且与水流流动条件有关，颗粒对水流结构的影响随着水力条件的变化而改变：在强水流条件下，不论粗、中、细泥沙都不改变主流区的流速分布及紊动强度；在中等强度水流条件下，粗、中、细三种颗粒的加入都使流速大于相同条件的清水水流，而其紊动强度则较清水水流低；在弱水流条件下，三种颗粒的加入都不改变水流的流速分布，但粗颗粒使水流紊动强度显著增大，而中、细颗粒基本不改变其紊动强度。     

淹没紊动射流三维流场特性的数值模拟

采用RNGk-ε紊流模型对有限空间的单孔、双孔紊动射流的流场进行了三维数值模拟研究。研究结果表明:无论入流条件如何变化,经无量纲处理后的轴线流速分布曲线几乎都落在同一条无量纲速度分布曲线上,说明流动存在相似性。双孔射流时,流场存在分区结构,在不同的喷嘴间距下,射流的卷吸程度不同,S/D越大,射流之间的卷吸掺混作用越弱。     

矩形水槽水流紊动特性分析

采用三维超声流速仪系统地测量矩形水槽水流紊动特性,对紊动拟序结构中的准周期、频率、周期函数、概率密度函数等进行了定量的数学描述,并对时均流速、紊动强度、雷诺应力等沿垂线分布问题作了较为深入的分析计算。为研究水流的紊动结构及悬移质泥沙的运动机理提供了验证资料,加深了对水流紊动结构的了解。     

常曲率U型弯道水流紊动特性试验研究

采用三维声学多普勒流速仪,对水流三维流速进行了采集,对弯道水流的脉动进行了统计分析,研究了典型断面的紊动强度、紊动切应力、紊动能的分布。试验结果能够很好的揭示弯道水流的三维特性及分布规律。研究成果为进一步研究水流的紊动结构及泥沙的运动机理提供了参考资料。     

射流冲沙研究

作者通过实验和分析，研究了横流中加入平面冲击射流对防止局部泥沙淤积的影响。水槽实验中观测了水射流局部紊动强度变化、射流冲沙范围内局部紊动剪应力分布、泥沙不淤积临界断面的底部垂向紊动强度和射流强度与泥沙防淤尺度的关系。得出了射流影响区水流紊动能随距离的衰减规律和保持泥沙不淤积所需的水流临界紊动强度。统计分析了射流强度与紊动能的变化关系。根据泥沙悬浮理论和射流紊动输沙机理，建立了水射流局部无泥沙淤积长度经验计算式，并以不同特性泥沙的射流输沙实验资料对所建立的计算公式进行了验证，二者吻合良好。     

Large eddy simulation of turbulent flow structure and characteristics in an annular jet pump

The large eddy simulation(LES) of the flow characteristics in an annular jet pump(AJP) is conducted, and the flow characteristics are systematically analyzed from both time-averaged and instantaneous aspects. The jet expansion, the velocity distribution and the energy are considered to analyze the time-averaged evolution of the flow field in the AJP. The transient flow characteristics can also be acquired from the analysis of the turbulence intensity and the Reynolds stress. The simulation demonstrates that in the time-averaged characteristics, the potential cores increase linearly with the increase of the flow ratio. With the flow development, the jet half-width gradually increases and the residual energy coefficient decreases. Compared with the distribution of the time-averaged axial velocity, that of the instantaneous velocity is more complex and disorderly. The high intensity of the axial turbulence mainly occurs in the mixing layer and the near-wall regions of the diffuser. The annular distribution of the Reynolds stress is mainly in the mixing layer and the recirculation region. There is a low-stress zone between the mixing layer and the high-stress region in the wall-boundary layer. The intensity of the spanwise vortexes is larger than that of the streamwise vortexes, and therefore, the former make greater contribution to the total vorticity. This research provides a better understanding of the flow characteristics in the AJP.     

THREE-DIMENSIONAL MEAN AND TURBULENCE CHARACTERISTICS OF AN IMPINGING DENSITY JET IN A CONFINED CROSSFLOW IN NEAR FIELD

The three-dimensional mean and turbulence characteristics of an impinging density jet in a confined crossflow were numerically investigated using the RNG turbulence model. The comparison of the subregion structures and gross features between the numerical results and the experimental data show good agreement. The velocity, Turbulent Kinetic Energy (TKE) and concentration distributions of the impinging jet in near field were obtained and analyzed. The results indicate that the flow and concentration fields of the impinging jet in the crossflow exhibit distinguished three-dimensionality in the near field. There exist upstream wall vortices and downstream wall jet zones in the impinging region, and the TKE and concentration decays are asymmetrical in relation to the stagnation point. The lateral concentration distributionrange in the impinging region spreads considerably. The enhanced entrainment and mixing of the impinging jet in the confined crossflow are mostly associated with the impinging action and lateral expansion in the impinging region. The presence of the bottom wall restrains the formation of the spanwise rollers in the transverse jet region and vertical entrainment and mixing in the impinging region and the transition region.     

浅尾水深水平底板上表面射流水力特性的数值模拟研究

采用VOF(volume of fluid)方法追踪自由液面,辅以Realizable(可实现化)湍流模型封闭两相流时均方程,对浅尾水深水平底板上的表面射流水力特性进行了数值模拟。微分方程的离散采用有限体积法,速度与压力耦合求解使用了压力隐式算子分裂PISO(Pressure-Implicit with Splitting of Operators)算法。研究并分析了入射速度、尾水深和进口宽度等对流场流线分布、速度场及横断面最大流速沿程衰减规律等水力特性的影响。研究发现:流场内存在一个大的漩涡,入射流速越大,漩涡长度越长;横断面上水平流速和纵向流速在漩涡区和明渠流区分布规律不同;横断面最大流速沿程衰减主要受进口流速大小的影响。     

THEORETICAL AND EXPERIMENTAL STUDY ON THE CONICAL SWIRLING WATER JET FLOW

This paper is concerned with theoretical and experimental study on theconical swirling water jet flow.Based upon the theoretical analysis,the experiment on thestructural characteristics of swirling water jet flow including the velocity and pressure dis-tribution laws,on which the parameters of the jet,nozzle and directional blades havemore or less influence,was carried out in CSSRC by using a 3-D LDV in order to optimizea new high-efficiency jet instead of swirling drilling bit for rock-breaking and continuouslydrilling,and to meet the demand of radial horizontal drilling technology.Meanwhile basedon the experimental results,the numerical simulation was conducted for the conicalswirling water jet in the immersed well-bottom flow by solving the RANS equations in the3-D body-fitted coordinate system with the k-ε turbulence model.The numerical resultsare consistent with the experimental data,and lead to some conclusions which are impor-tant for applying the conical swirling water jet to the petroleum drill     

横流中射流及其温度标量输运大涡模拟

将动力拟序涡黏性亚格子应力模型拓展到温度标量亚格子模型中,数值模拟了横流条件下有、无温度标量场作用的射流,得到的横流条件下浮力射流的温度和速度分布与Anwar的试验值吻合一致。在此基础上,分析了有、无温度标量场作用下射流回流区域大小和射流轨迹线特性,对比分析了回流区域内涡心和分离点处湍动能和耗散率、拟涡能以及边界层处拟序结构等湍流特性。计算结果表明:温度场的作用使射流的回流区域增大,射流速度轨迹线高度增加,回流区域内湍流的湍动能增加,边界处拟序结构的周期性不如无温度场时明显。     

Velocity and concentration measurements in initial region of submerged round jets in stagnant environment and in coflow

Velocity and concentration fields are measured in submerged round jets in a stagnant environment and in coflow using laser Doppler anemometry and laser-induced fluorescence. Measurements are made in the initial region within distances of 40 jet exit diameter at jet Reynolds number between 1000 and 5000 and coflow-to-jet velocity ratio from 0 to 0.43. Different behaviors of jet spreading and dilution are found in jets at three different ranges of Reynolds number in which the jets are classified as initially laminar, transitional or turbulent. In the zone of established flow, the jet centerline velocity and concentration decay with downstream distance at different rates in the three groups of jets. For jets in coflow, axial development of normalized forms of centerline mean excess velocity and mean concentration at different velocity ratios can be reasonably well collapsed onto universal trends through the use of momentum length scale. Turbulence properties inside a jet are increased by the presence of a strong coflow. Inside the zone of flow establishment, some strange features are observed on jet turbulence properties. The length of zone of flow establishment increases from the turbulent jets, to the transition jets and to the laminar jets. The zone lengths for concentration are shorter than those for velocity by one to two jet exit diameters. Both lengths are shortened further in the presence of a coflow. For jets a stagnant environment and in the strong jet flow region of jets in coflow, jet widths increase linearly with downstream distance in transitional and turbulent jets. Self-similarity of radial profiles of mean velocity or excess velocity, mean concentration, turbulence intensities and concentration fluctuation level is explored in the zone of established flow.     

NUMERICAL SIMULATION OF TURBULENT JETS WITH LATERAL INJECTION INTO A CROSSFLOW

1. INTRODUCTION The interaction of jets with crossflow generates complex flow fields which exist in a variety of industrial applications, e.g. internal film cooling of turbine blades, dilution air jets in combustion chambers, jet from V/STOL aircraft in transition flight. Systematic experimental, theoretical and numerical investigations of the flow fields began several decades ago, where the parameters studied include the jet injection angel, the jet-to-crossflow velocity ratio, the jet …     

Numerical simulation of slurry jets using mixture model

Slurry jets in a static uniform environment were simulated with a two-phase mixture model in which flow-particle interactions were considered. A standard k-ε turbulence model was chosen to close the governing equations. The computational results were in agreement with previous laboratory measurements. The characteristics of the two-phase flow field and the influences of hydraulic and geometric parameters on the distribution of the slurry jets were analyzed on the basis of the computational results. The calculated results reveal that if the initial velocity of the slurry jet is high, the jet spreads less in the radial direction. When the slurry jet is less influenced by the ambient fluid (when the Stokes number St is relatively large), the turbulent kinetic energy k and turbulent dissipation rate ε, which are relatively concentrated around the jet axis, decrease more rapidly after the slurry jet passes through the nozzle. For different values of St, the radial distributions of streamwise velocity and particle volume fraction are both self-similar and fit a Gaussian profile after the slurry jet fully develops. The decay rate of the particle velocity is lower than that of water velocity along the jet axis, and the axial distributions of the centerline particle streamwise velocity are self-similar along the jet axis. The pattern of particle dispersion depends on the Stokes number St. When St = 0.39, the particle dispersion along the radial direction is considerable, and the relative velocity is very low due to the low dynamic response time. When St = 3.08, the dispersion of particles along the radial direction is very little, and most of the particles have high relative velocities along the streamwise direction.