旋转槽道内部流动结构的识别与分析

基于旋转湍流是典型的各向异性湍流,在大气、天体和旋转机械的湍流运动中必须考虑旋转效应。该文采用大涡模拟的方法对一旋转槽道流进行数值模拟,考察了旋转效应在湍流场中非线性的能量输运机制,并采用不同的涡显示方法对旋转槽道中的湍流结构的演化规律进行了分析。     

曲率对边界层湍流结构的影响

本文计算了沿不同曲面流动的湍流边界层。提出了考虑曲率影响的双方程湍流模式。通过与实测的穿过边界层的湍流能量和结构系数分布的数据比较,分析了曲率对边界层的影响。结果发现,曲率对边界层湍流结构的影响小于旋转的影响,但在不旋转的蜗壳中,不能略去曲率的影响。     

一种适于强分离流动的三方程VLES模型

强分离流动的准确模拟对湍流模型极具挑战性，导致现有的VLES模型仍难以满足要求。究其原因，强分离流动往往伴随分离涡且具有局部旋转特征，而现有模型往往并未考虑该效应。为此，该文基于旋转湍流中表现优异的k-ω-v²模型，建立了一种新的VLES模型，并将其应用于圆柱绕流中，结果表明：相比现有的VLES k-ε模型，新模型准确地预测了圆柱后方的回流区长度，且雷诺应力的预测明显占优。通过精度控制函数及几个相关尺度的分析，发现湍流积分尺度是关键影响因素，新模型得到了该尺度的合理值，而VLES k-ε模型则高估了该值，导致精度控制函数偏低而预测失真。     

水力机械中固液两相流研究——水力机械中固液两相流基本方程组

本文建立起了水力机械中固液两相流的基本方程组,对于层流流态,方程组是封闭的;对于湍流流态,方程组是不封闭的,需要相应的湍流模式。导出了旋转相对坐标系上固液两相相互作用力的表达式,与绝对坐标系上的相比,它包含了向心惯性力和科氏惯性力。     

任意拉格朗日—欧拉（ALE）法求解三维湍流流动

本文推导了旋转叶轮内流湍流Ｎ－Ｓ方程计算的ＡＬＥ格式。以网格的虚拟运动计算对流作用；采用粘性子循环时步、拉格朗日子循环时步加速收敛；改进上风格式为部分施主单元格式来减小扩散同时实现良好的计算性能；由通量限制控制耗散截断误差；计算中引入短波长阻尼以消除不规则性；以亚网格（ＳＧＳ）湍流模式模拟湍流运动。     

水力机械中固液两相流研究—水力机械中固液两相流基…

本文建立起了水力机械中固液两相流的基本方程组，对于层流流态，方程组是封闭的，对于湍流流态，方程组是不封闭的，需要相应的湍流模式。导出了旋转相对坐标系上固液两相相互作用力的表达式，与绝对坐标系上的相比，它包含向心惯性力和科氏惯性力。     

滑移网格下泵内流场的非定常流计算

该文在OpenFOAM开源平台下,采用滑移网格方法对二维泵内流场进行了非定常流数值计算.计算区域分为旋转区和静止区,滑移界面通过GGI算法实现变量插值和传递.并分别利用RANS和LES模型进行模拟,研究了不同湍流模型对非定常湍流场计算的影响.计算结果表明,动静叶相互作用下的流场具有明显的瞬态特征,其中LES模拟能更好预报流场的大尺度脉动特征.并将该文计算的瞬时速度分布与实验数据进行了比较,结果表明该文的滑移网格数值方法具有较好的适用性.     

挟沙水流幂律湍流模式研究

围绕如何描述挟沙水流湍流特性和确定湍流模式这一工程设计所关心的问题,建立了一种合理实用的挟沙水流湍流特性表达式。通过湍流理论分析和挟沙水流湍流特性试验,构建了与浑水含沙浓度相关的一种非牛顿切应力型湍流模式——幂律湍流模式,进而求解雷诺方程得到挟沙水流的流速分布,回归分析挟沙水流湍流特性试验数据,率定流速分布表达式参数,从而确定挟沙水流幂律湍流模式参数。     

液--液旋流分离管中强旋湍流的RNG k-ε数值模拟

在高雷诺数时，ＲＮＧｋ－ε模型在形式上与标准ｋ－ε模型基本相同，其区别主要是在ε方程中增加一个附加生成项。当流动快速畸变时该项迅速增大，由此改善了对旋转流、浮力流等较复杂湍流的预报能力。本文应用该模型对液－－液旋流分离管中强旋湍流场的数值计算结果表明，其结果虽较标准ｋ－ε模型有所改善，但同实际值间仍存在定性上的不合理性，因此，要在更大程度上改进对液－－液旋流分离管中强旋湍流的预报，必须放弃基于各向     

同轴旋转分层流燃烧器空气动力场的数值模拟

同轴旋转分层流燃烧器运用离心力分层原理，对一、二次风混合进行有效控制，达到分级燃烧，抑制NO，生成的目的。由于离心力的作用，同轴旋转分层流燃烧器的湍流脉动是各向异性的，这使得基于各向同性假设的k-e模型不再适用。本文运用作者提出的考虑离心力影响的k-e模型(k-e-cf模型)，对流项采用混合差分格式，对同轴旋转分层流燃烧器空气动力特性进行了数值模拟，将数值预报与实验测定进行了比较，得到了较好的结果。     

用水轮机能量特性比较稳定性：紊流损失分析法

变换欧拉方程式推导出紊流方程式，该方程提出了“虚拟最优工况”的概念，将转轮前后的紊流流态分析离出来，利用水轮机的能量特性计算紊流损失，比较其大小，以判断运行的风险。     

THE TURBULENCE CHARACTERISITICS OF OPEN CHANNEL FLOW

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

圆端形桥墩侧向紊流宽度的试验研究

在水槽中进行概化试验,采用三维声学多普勒测速仪(ADV)测量圆端形桥墩周围三维流场及紊动强度分布.分析有桥墩时的紊流强度垂向分布及有、无桥墩时紊流强度比值的横向分布变化,分析结果表明,垂线上紊流强度最大位置在0～0.2 h与0.8h～1.0h两个区间,桥墩对紊流强度的变化影响存在极值,极值大小和出现位置与流速有关,流速越大,极值越大,且极值位置与桥墩的距离也越大.根据极值出现位置离桥墩距离确定紊流宽度,给出了桥墩紊流宽度与弗汝德数的关系.     

明渠紊流与床面形态相互作用研究进展

结合国内外最新研究动态,从明渠紊流与床面形态相互作用的研究方法、明渠紊流特点、紊流对沙波形态的影响、床面形态对紊流的反作用等方面对明渠紊流与床面形态相互作用进行了综述。当前明渠紊流特性、二维沙波床面水沙运动特性等方面的研究已经取得丰富成果,但尚不能很好地解释天然河流中的水沙输移机理;由于试验测量方法的限制,复杂床面条件下的水沙相互作用研究在相当长时间内没有取得突破性的成果,亟需探索和引入无干扰、高精度的三维瞬态全场测量技术;床面几何形态、沙波发展演变方面的研究相对成熟,但床面的稳定机理尚存在分歧,理论模型和数学模型均不够完善,尤其沙波内部渗流与明渠紊流综合作用下的床面稳定性和泥沙运动特性研究还比较少,是今后进一步探索的方向,其成果可为揭示三维沙波床面紊流与泥沙相互作用机理提供必要的前提。     

Turbulence characteristics in free-surface flow over two-dimensional dunes

The turbulent structure of open-channel flows over two-dimensional dunes is investigated numerically using large-eddy simulation (LES), in order to improve our understanding of the interaction between the dune-generated turbulence and the free surface dynamics. The filtered Navier–Stokes equations in the LES model have been discretised using the finite volume method, with a dynamic sub-grid model being employed for the unresolved scales of turbulence. The partial cell treatment has been implemented in a Cartesian grid form to deal with the dune topography. Both the volume of fluid method and rigid lid approach have been employed in the numerical framework to investigate the effects of the free surface treatment on the flow characteristics. The numerical model predicted mean flow velocities, turbulence intensities and Reynolds stresses have been compared with experimental measurements published in the literature, with a detailed analysis being undertaken to assess the accuracy of the model results and the effects of the free surface treatment on the velocity and turbulence predictions. The instantaneous flow structure has been investigated, with emphasis being focused on the free surface dynamics and coherent structures.     

PIV and PTV measurements in hydro-sciences with focus on turbulent open-channel flows

PIV is one of the most popular measurement techniques in hydraulic engineering as well as in fluid sciences. It has been applied to study various turbulent phenomena in laboratory experiments related to natural rivers, e.g., bursting phenomena near the bed, mixing layers observed at confluences, wake turbulence around dikes and piers, and so on. In these studies, PIV plays important roles in revealing the space-time structure of velocity fluctuations and coherent vortices. This review article focuses particularly on the applications of PIV to turbulent open-channel flows, which have been conducted for the past decade in Hydraulics Laboratory of Kyoto University. In Section 2, we introduce our experimental setup and PIV/PTV algorithm. In Section 3, we apply the PIV measurements to reveal turbulence characteristics and coherent structures in open-channel flows as well as in vegetated canopy flows. For complex flow situations, various applications of PIV to compound open-channel flows and wind-induced water waves are considered to reveal coherent vortices. In Section 4, we discuss some advanced PIV measurements in open-channel flows. The free-surface-elevation fluctuations and velocity components were measured simultaneously with two sets of cameras to examine phase-averaged parameters of turbulence. A multi-layer scanning PIV was developed to reveal 3D turbulence structure in compound open-channel flows. Our discriminator PIV/PTV was applied successfully to sediment-laden open-channel flows and revealed the fluid/particle interaction and the relationship between coherent structures and sediment concentration. Finally, we conducted simultaneous measurements of velocity and dye concentration with a combination of PIV and LIF in vegetated open-channel flow, which enables us to examine turbulent scalar flux of a passive contaminant.     

随机波浪边界层的数值模拟与分析

该文基于雷诺平均的Navier-Stokes方程和k-ω两方程紊流模型建立了随机波浪边界层数学模型,模拟了粗糙底床上方的随机波浪边界层流速、床面剪切应力和紊动能量分布,计算结果与实测数据吻合良好。探讨了随机波浪边界层水动力特性,发现随机波浪时间序列中各个子波的紊动能量近似随该子波均方根自由振荡速度平方的增大而线性增大,但各个子波的紊动能量还受到上一个子波紊动能量传递的影响,体现了随机波浪与规则波浪的区别。整个随机波浪时间序列的有效摩阻系数和单个子波的摩阻系数均与前人实验数据和经验公式较为一致。     

A preliminary study of the turbulence features of the tidal bore in the Qiantang River,China

In this paper, the turbulence characteristics of the tidal flow in the Qiantang River, China, the world-famous Qiantang bore, are studied. A detailed field observation at the Yanguan section of the Qiantang River was carried out during the spring tide in October 2010 with a continuous collection of high frequency turbulence data. The data analysis shows that the hydrodynamic processes are characterized by a strong tidal bore. Statistics of the turbulence such as the probability distributions of the turbulent components, the variance terms and the covariance terms are found consistent with those of previous studies of estuaries without the tidal bore. However, along the vertical profile, the distributions of all variables become more scattered downwards. The horizontal turbulence fluctuations are of a similar magnitude while the vertical turbulence has a fluctuation magnitffde about 1/3 of that of the horizontal turbulences. The fluctuation strengths and the Reynolds stresses are much larger than those of other estuaries when the bore arrives. The bottom shear stress varies periodically with the tides, less than 0.44 N/m2 during the ebb but is increased drastically at the bore arrival, with the maximum being 0.92 N/m2. A good linear relationship is found between the bottom shear stress and the bottom suspended sediment concentration.     

THE APPLICATIONS AND STUDY OF NUMERICAL SIMULATION OF TURBULENCE FLOW WITH FREE SURFACE IN HYDRAULIC SPILL WAYS STRUCTURE

The turbulence flow Free Surface has important applications in hydraulic spillways structure,such as the hydraulic jump,energy dissipation flow etc.This is being considered as very complicated flow,and has not yet been solved quite well by numerical method. In this paper,a Large-scale computational software package are developed for numerical laboratory of hydraulic spillway structure.Some methods,such as turbulence model, free surface and irregular boundary treating techniques,scientific computer visualization are put forward and performed.