喷嘴与水平圆管的气—液两相流动阻力特性

本文应用一维变密度气－液两相流动量于喷嘴和水平圆管的气水两相流动，建立了喷嘴进口压力及流速之间的关系，将动量方程在有限管道长度内积分，从而可由试验得的压力差计算通过水平圆管的气－液两相流阻力系数，并在大量试验的基础上建立了考虑截面含气率的喷嘴动量修正系数的相关关系式和水平圆管中大气两相流阻力系数与雷诺数之间的关系式。     

喷嘴与水平圆管的气－液两相流动阻力特性

本文应用一维变密度气－液两相流动量方程于喷嘴和水平圆管的气水两相流动，建立了喷嘴进出口压力及流速之间的关系，将动量方程在有限管道长度内积分，从而可由试验测得的压力差计算通过水平回管的气－液两相流阻力系数，并在大量试验的基础上建立了考虑截面含气率的喷嘴动量修正系数的相关关系式和水平因管中气水两相流阻力系数与雷诺数之间的关系式。     

垂直上升气液两相流中三角形柱体两相斯托拉赫数的研究

本文试验研究了两种规格三角形柱体，在垂直上升气液两相流中，发生气液两相涡街时，气液两相斯托拉赫数的变化规律。在测得大量数据的基础上，得出了发生气液两相涡街时，气液两相斯托拉赫数的通用关系式，研究表明，气液两相斯托拉赫数在两相工况下为一变数，与来流截面含气率、涡街发生体形状和特征尺寸、来流方向等因素有关，应用此关系式，根据测得的两相涡街频率可钎涡街发展体作为测量两相流流量与组分的测量元件。     

气—固两相流边界层双向耦合模型及其应用

本文提出了一种稀相的气－固两相流边界层的双向耦合模型，在对固壁附近的粒子源项作子特殊处理后，利用此模型研究了流经平面叶栅的气－固两相流中的固体粒子越边界层时受到的影响以及粒子存在对边界层内气体流动的反影响。其中粒子运动特的计算结果与试验进行了对比分析。     

压力脉冲在井眼气－液两相流传播的数值模拟

本文对压井期间节流阀调节过程中压力脉冲在井眼环空气－液两相流中传播速度进行了数值模拟。建立并求解了一维拟线性双曲型偏微分方程组，从而能够给出气侵后环空气－液两相流分布和在压井期间的气－液两相流分布。同时导出了压力脉冲在气－液两相流中传播速度公式，给出了计算节流阀调节间隔计算方法。举例计算出了节流阀调节后压力脉冲经过钻柱泥浆及环空流体中传播时间。利用本方法可以适时调节节流问，使压井期间井底保持较恒定的压力，从而真正符合并控理论。     

表面活性剂对气液两相螺旋管流流动特性的影响

为了考察阴离子型表面活性剂十二烷基硫酸钠(SDS)对气液两相螺旋管流流动特性的影响,该文用实验研究了不同浓度的SDS溶液体系气液两相螺旋管流的流型转变及压降规律。实验装置为由有机玻璃圆管制成的长2 m内径23 mm的实验段,以SDS水溶液和空气为实验介质,气液相折算流速均为0―2.5 m/s,SDS溶液质量浓度10―90 mg/kg,螺旋流由5种不同型号的金属螺旋叶轮诱导产生。利用直接观察和高速摄像相结合的方法观测流型的变化,并用液柱式压差计测量实验管段上下游间压差,实验在常温常压条件下进行。实验共得到螺旋线状流、螺旋波状分层流、螺旋轴状流、螺旋弥散流4种流型,与未添加表面活性剂体系相比较,并未得到螺旋泡状流和螺旋团状流这两种流型。同时,随着SDS溶液浓度的增大,气液两相螺旋流逐渐向螺旋弥散流流型转变,这是因为低浓度的SDS溶液随着其浓度的增大,气液界面张力逐渐减小,而气液掺混程度则会不断增大。此外,与未添加表面活性剂体系相比较,添加了SDS体系的气液两相螺旋管流压降梯度将会减小。最后,阐述了气液两相螺旋管流强化天然气水合物生成的研究及应用现状,并针对多相流研究现状,提出了气液两相流相间传热特性应成为今后研究热点等建议。     

垂直下水管中气液两相流动特性分析

由于山区水资源空间分布不均,我国边远山区存在结构性缺水的问题。低落差河流环境下液气泵系统是解决该问题的一个有效方案,而垂直下水管及其涉及的气液两相流动特性是其重要的组成部分及关键技术。基于提出的均相流模型和多工况试验数据,对垂直下水管中的气液两相流运动特性进行了进一步研究。重点研究了能够反映垂直下水管中的气液混合程度的关键参数与各个影响因素之间的关系。通过试验结果与解析解的对比,进一步分析并论证了均相流模型存在的不足和试验设计的欠缺之处,为垂直下水管道直径的选取提出了建议。     

曝气池中气液两相流速度场分布的实验研究与数值模拟

气液两相流广泛存在于水利工程、废水处理等领域,其在气液装置中的流型流态及速度场分布可直接影响装置运行效能。本文采用实验研究与数值模拟相结合的方法,对圆柱形气液装置进行PIV实验,获得了准确的气液两相流气相速度场分布;在充分考虑湍流、曳力、升力、湍流分散力等作用下,采用欧拉-欧拉双流体模型和气泡群平衡模型对气液两相流流场进行了数值模拟,并将模拟结果与实验结果进行验证,所得结果误差控制在10%左右。结果表明,本文提出的模拟方法在气液两相流模拟中能够得到较准确的两相流动规律和速度场分布情况。     

稠密固液两相流管道絮凝研究

通过对前人有关稠密固液两相流管道絮凝过程的研究回顾与分析，基于管道中流体运动处于紊动状态这一事实，推导出了新的管道中稠密两相流体紊乱的平均流速梯度G（即絮凝强度）的计算公式，克服了以往有关教科书存在的物理概念和数学推导方面的缺陷。利用该公式并结合试验对管道絮凝过程的最佳GT值进行了研究，得出当GT＝60－120时，稠密固液两相流管道絮凝效果最佳。     

曝气池中气液两相流的数值模拟与实验研究

曝气在活性污泥处理方法中起着重要的作用，而曝气池中气液两相流流动规律对曝气作用的影响又至关重要。本文通过实验研究了曝气池中气液两相流的流动问题。在此基础上建立了气液两相紊流的流动模型，并采用单位体积方法进行求解计算，经比较表明实测值与计算值吻合较好。     

滤料气水反冲洗性能的人工神经网络模拟研究

对3组不同滤料的气水反冲洗性能的正交试验结果,用神经网络方法进行建模研究。建模实践表明:人工神经网络方法适合于滤料反冲洗的灰箱和黑箱系统的建模。建立了滤料气水反冲洗耗水量的BP人工神经网络模型,以便对变量进行重要度和灵敏度分析。在研究的空气反冲洗强度、水反冲洗强度、气水同时反冲洗历时、单水漂洗强度和池型5个变量中,水反冲洗强度最重要,空气反冲洗强度最不重要,为研究在保证清洁度的前提下有效降低气水反冲洗耗水量提供了理论依据。     

Unstructured finite volume method for water impact on a rigid body

A new method is presented for the water impact simulation, in which the air-water two phase flow is solved using the pressure-based computational fluid dynamics method. Theoretically, the air effects can be taken into account in the water structure interaction. The key point of this method is the air-water interface capture, which is treated as a physical discontinuity and can be captured by a well-designed high order scheme. According to a normalized variable diagram, a high order discrete scheme on unstructured grids is realised, so a numerical method for the free surface flow on a fixed grid can be established. This method is implemented using an in-house code, the General Transport Equation Analyzer, which is an unstructured grid finite volume solver. The method is verified with the wedge water and structure interaction problem.     

基于数字图像处理的掺气水流 气泡分布研究

通过试验室研究,借助高速数码摄像机,结合VC高级编程技术,开发掺气水流气泡分析 软件,提出一种自动识别水气两相流中气泡的数字图像处理方法,为图像处理技术与水气两相流 实测研究相结合的尝试和探索。研究成果将提高对高速水流掺气机理的认识,为今后进一步深入 研究图像处理技术在水流流场特别是高速水气两相流流场测量中的应用打下良好的基础,对提高 掺气浓度的测量水平和精度,进而提高水力模型试验水平、满足工程设计要求等都具有较高的学 术意义和实用价值。     

气水两相流模型试验条件与掺气浓度相似律

从气体运动状态方程出发,研究了竖井有压流动模型中气水两相流的运动规律,分析了气泡几何相似、运动相似以及动力相似的条件,指出掺气浓度相似律是研究气水两相流相似问题的又一必要条件,即原、模型的掺气浓度必须相等,前提为大气压强或密度相似。对照公伯峡水电站竖井水平旋流洞原型与常压模型水流中掺气浓度测值的差异,给出了该竖井流态、压强、流量等不相似现象的合理性解释。依据掺气浓度相似律准则进行气水两相流模拟研究,对于发展传统水力学研究理论、创新研究方法、完善工程应用技术等,可以起到有效的推动作用。     

Effects of Surface Films on Air-Water Exchange Rates

The effects of surface films in reducing air-water exchange rates are discussed, an example being given to illustrate effects on solute concentrations and persistence. It is suggested that films may have two additive retarding effects. First is a hydrodynamic effect in which turbulence in the interfacial region is rendered more sluggish, this effect being identifiable by changes in drag coefficient, friction velocity, and surface roughness. Second is a diffusive resistance effect for which a three phase resistance model is derived. The effects are combined to give model results which compare favourably with experimental data. Suggestions are made for experimental testing of the model hypotheses.     

THEORETICAL AND EXPERIMENTAL INVESTIGATIONS OF ENTRAINED AND TRANSPORTED CHARACTERISTICS OF SUBMERGED JET

This paper presents entrainment mechanism, and transported and diffusion characteristics at the point of entry of submerged jet. The profiles of both velocity and concentration within the air water mixing layer were theoretically deduced. And the comparisons between theoretical values and measured data were made. Results show that the velocity profile within the air water mixing layer exhibits a form of error function. The concentrations of air entrainment in the internal and external regions of ai~water mixing layer correspond to Gaussian distribution.     

Estimation of Overlake Wind Speed from Overland Wind Speed: A Comparison of Three Methods

Meteorological data gathered by buoys in Lake Erie and recorded at overland weather stations were used to test three different methods for determining overlake wind speed as a function of overland wind speed and the difference between overland air temperature and water temperature. The overall root mean square differences between estimated and observed overlake wind speed ranged from 2.02 to 2.11 m s^?1. Overall correlation coefficients ranged from 0.63 to 0.69. These values are close to the best values possible for a simple statistical formula relating overlake wind speed to overland wind speed and air-water temperature difference. The conclusion is that statistical methods for determining overlake wind speed from overland wind speed have not improved markedly in over a decade and new methods are called for. It is also shown that for the Great Lakes, as opposed to the open sea, air-water temperature difference is a significant factor in determining overlake from overland wind speed.     

溢洪道挑流消能数值模拟计算模型的选择

采用数值模拟的研究方法,以溢洪道为研究对象,分别采用标准k-ε模型与RNG k-ε模型,对溢洪道进行二维水气两相流数值模拟,通过与物理模型试验数据相对比,探究不同计算模型对溢洪道数值模拟计算所得数据的准确性。经验证标准k-ε模型计算所得结果较为准确,且耗时较短。     

Anisotropic diffusion of volatile pollutants at air-water interface

The volatile pollutants that spill into natural waters cause water pollution. Air pollution arises from the water pollution because of volatilization. Mass exchange caused by turbulent fluctuation is stronger in the direction normal to the air-water interface than in other directions due to the large density difference between water and air. In order to explore the characteristics of anisotropic diffusion of the volatile pollutants at the air-water interface, the relationship between velocity gradient and mass transfer rate was established to calculate the turbulent mass diffusivity. A second-order accurate smooth transition differencing scheme (STDS) was proposed to guarantee the boundedness for the flow and mass transfer at the air-water interface. Simulations and experiments were performed to study the trichloroethylene (C₂HCl₃) release. By comparing the anisotropic coupling diffusion model, isotropic coupling diffusion model, and non-coupling diffusion model, the features of the transport of volatile pollutants at the air-water interface were determined. The results show that the anisotropic coupling diffusion model is more accurate than the isotropic coupling diffusion model and non-coupling diffusion model. Mass transfer significantly increases with the increase of the air-water relative velocity at a low relative velocity. However, at a higher relative velocity, an increase in the relative velocity has no effect on mass transfer.     

RE-AERATION LAW OF WATER FLOW OVER SPILLWAYS

1. INTUODUCTION Due to the strong turbulence of the flow over the spillway, air is entrained into water body making the oxygen content increased. It is important for river, especially for city-river to maintain favorable water quality and ecological envir…