紊流

In this paper, a three-dimensional multi-level hydrodynamic model with curvature correction in curvilinear coordinates has been developed based on the update turbulent theory and numerical method, which can effectively solve the practical problems of flows and water quality transportations in hydraulic engineering, and can strengthen the practical usage of the mathematical model.

本文基于现代紊流理论、现代数值计算方法建立适合描述水利工程中紊流规律的非线性数值模型，即曲线坐标系下的多层紊流水动力模型，旨在提高紊流精细模拟的实用性，以求有效地解决水利工程中的水流和输运现象的实际问题。

Main creative points of the thesis are as following:1. It is the first time to apply 2-D and 3-D turbulent model of the air-water two phases flow to the study on hydraulic properties of groyne. It makes description of the turbulent flow field to be possible precisely. This offers a more accurate method to determine the water surface in channel improvement.2. Based on the results of experiment and simulation for 3-D turbulent model of air-water two phases flow, a new formula to compute the height of damming is built.3. Based on the 2-D mode and the formula to compute the height of damming, the subdivision method of 2-D computation for water surface at upstream and downstream.

本文的创新工作主要是：首次将三维水气两相流紊流数学模型应用于丁坝水动力学特性研究，使丁坝附近流场和紊动场的精细描述成为可能，为航道整治中水面线确定提供了一个更为准确的方法；(2)基于水槽实验和三维水气两相流紊流数学模型数值模拟结果，建立了新的丁坝前奎水高度计算公式；(3)基于上述奎水高度计算公式和本文二维水面计算数学模型，首次提出了丁坝上下游二维水面分段计算方法。

In this thesis, study is on the basis of N-S equation and standard turbulent flow mould. Numerical simulation is given to turbulent flow inside impeller of LB50-160 type centrifugal pump.

本文基于N-S方程和标准k-ε紊流模型，对LB50-160型离心泵设计流量下叶轮内流场三维紊流进行了数值计算，获得了叶轮内流场的速度、压力分布，捕捉到了一些重要的流动现象。

Numerical simulation to three-dimensional turbulent flow in multistage axial compressor blade row is carried out, where high resolution third-order ENN scheme is adopted to catch the shockwave and simulate the turbulent flow correctly, and LU-SGS implicit method is chosen to improve computation rate. A nicety and high efficiency numerical simulating system is thus constructed.

对多级轴流压气机叶栅内三维紊流流场进行数值模拟，采用高精度高分辨率的三阶ENN格式以保证对激波的捕捉和对紊流特征的正确模拟，利用LU-SGS隐式解法提高了计算速度，从而构成了一种既准确又高效的多级跨声速轴流压气机紊流流动数值求解系统。

Considering the characters of the viscoidal turbulent flow over high-speed train,the computing model of the outer fiow field for high-speed train has beenestablished based on the incompressible fluid Navier-StOkes epuation and theturbulent model of ke two equations. The equation set of the flow field problemvia finite element methods has been set up.

根据高速列车粘性紊态绕流的特点，在较少简化的条件下以Navier-Stokes方程和κ-ε两方程紊流模型为基础，建立了高速列车外流场的计算模型，在近壁区域采用壁面函数修正紊流模型。

The results of this study indicate that changing the angle of the intake port has a profound effect on the flow field during the intake stroke of the engine cycle. For the case with the intake-exhaust valves canted at zero degree (the so-called vertical valves), the tumble ratio, swirl ratio, turbulent intensity, and turbulent kinetic energy in the direction perpendicular to the bisecting plane of the cylinder are at their highest levels than those obtained for the other cases. This effect is most pronounced after the compression stroke of the cycle. As a result of this study, it is observed that the behavior of the overall flow field from the intake to the completion of compression stroke has a major impact on the effectiveness of the mixing of fuel-air prior to the ignition of the engine cycle.

结果显示，改变进排气阀的倾斜角度对进气期间的流场变化有很明显的影响，其中以垂直阀(进排气阀倾斜0度)所得的 Y轴向(Y方向系垂直於将汽缸对分为二平面的方向)滚流强度、涡漩比、紊流强度、紊流动能等流场强度为最强；若以流体经活塞压缩后的流场特性进行探讨，所得结果显示压缩冲程对汽缸内流场的效应是不容忽视的；因此由进气到压缩过程结束的整体流场现象，才是影响引擎点火前的油气混合程度与燃烧品质的关键。

In our research, a 3-D numerical simulation calculation of the outside flow field of the flat-headed van-body truck has been made first. A RNG k-? turbulence model which can increase the calculation precision of the separation flow has been adopted, and the results show that the calculation of the van-body truck with the RNG k-e turbulence model is more exact than that of the standard k-e turbulence model.

本研究首次对平头厢式货车外部流场进行了三维数值模拟计算，模拟采用可以提高分离流计算精度的RNG k-ε紊流模型，计算结果表明其计算精度较标准k-ε紊流模型有显著的提高。

PDA(particle dynamics analyzer system) was used to measure the flow velocity of particles in the XFD-12 flotation cell, the results show that tangential mean velocity in the radial direction changes from positive to negative in the flotation cell, naught point emerge in the medium of the radial direction ,it is where backward fluid emerge ,shear stress of backward fluid induce the particle detachment from bubbles .

汁算数据与实际矿石筛析结果都表明，紊流强度增大，泡沫中粗粒级含量减小。 4。用PDA在XFD-12型8L浮选机中测定的速度值，进行混合区、分离区、泡沫区紊流运动功率谱计算，得紊流脉动频率，混合区小于20Hz，分离区在20-30Hz之间，泡沫区在25-35Hz之间，浮选槽内紊流脉动以低频为主，且紊流脉动动能是混合区大于分离区大于泡沫区。

An advanced combined turbulent lubrication model is proposed: low turbulence Reynolds number k-e model is used to describe the flow in the near-wall regions, and algebraic Reynolds stress model is used to describe the flow in the turbulence kernel, with flow continuity kept between the two models and transition criterion set to fit Leutheusser's measurements.

提出了先进的复合型紊流润滑理论：以低紊流雷诺数k-e模式描述近壁区内的流场，而以代数雷诺应力模式描述紊流核心区内的流场，二区间流场连续过渡，并依据Leutheusser实验结果设定过渡准则。

The previous researches have been done experiments mostly in the Water tank. In order to simulate turbulence of flow in river and research its characteristics, the characteristics of turbulence are studied by experiments in the water channel with ADV technique. The research results indicate that R.M.S. velocity linearly relates to the oscillating-grid frequency; R.M.S. velocity decays by power exponent relates to the distance from the grid midplane; and the relationship between the geometrical factors and the free movement space of water is direct proportion.

以往研究大都在水箱中对振动格栅紊流特性进行实验研究，为能模拟天然河道中的紊流，研究天然河道中紊流特性，利用ADV技术在水槽中对振动格栅紊流进行了实验研究研究结果表明：均方根速度与格栅振动频率成线性关系；均方根速度与距格栅中平面的距离成幂指数关系衰减；几何系数与水的自由运动空间成正比关系。

It has been put forward that there exists single Ball point and double Ball points on the symmetrical connecting-rod curves of equilateral mechanisms.

从鲍尔点的形成原理出发，分析对称连杆曲线上鲍尔点的产生条件，提出等边机构的对称连杆曲线上有单鲍尔点和双鲍尔点。

The factory affiliated to the Group primarily manufactures multiple-purpose pincers, baking kits, knives, scissors, kitchenware, gardening tools and beauty care kits as well as other hardware tools, the annual production value of which reaches US$ 30 million dollars.

集团所属工厂主要生产多用钳、烤具、刀具、剪刀、厨具、花园工具、美容套等五金产品，年生产总值3000万美元，产品价廉物美、选料上乘、质量保证，深受国内外客户的青睐