【作者】 周丰；

【导师】 孙昭晨； 梁书秀；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2007， 博士

【摘要】 水污染的治理关键是污染源的控制，造成水环境污染的主要原因之一就是城市污水的无序排放。由于污水江河湖海处置的工程造价和运行费用相对较低，污水江河湖海处置已经成为解决城市水污染优先考虑的工程措施。科学的设计污水排放方式和科学的选择排放水域都有赖于对排放到环境水体中污水的动力特性以及污染物扩散、输移特性等环境水力学问题的深刻认识。污水通常以射流的形式排放到江河湖海中，系统开展动水环境中射流特性的基础性研究不仅可以加深对湍流的认识，而且能够为射流在生产实践中的应用提供更加完善的理论基础，有着重要的科学价值和实际意义。本文从物理实验和数值模拟两方面对动水环境中射流特性，包括射流的流态、射流扩展率以及污染物浓度场分布特性等进行了较为系统的研究。在实验方面，利用波浪水槽结合粒子图像测速(PIV)系统对波浪环境中圆形垂向射流流场的时均特性和紊动特性进行了研究；在数值模拟方面，以Reynolds时均方程为基本控制方程，利用应力代数紊流模型和VOF方法建立了可模拟带自由表面的紊动射流二维数学模型和三维数学模型，对动水环境中窄缝射流和圆形射流进行了数值模拟，分析了横流环境中射流喷角对射流特性的影响，开展了波浪环境中窄缝射流和圆形射流基本特性的系统研究。本文基于不同波要素波浪环境中射流流场实验结果，分析、总结了波浪周期对射流核长度、横剖面上射流垂向平均速度分布以及射流扩展率的影响规律。根据对波浪环境中射流紊动特性实验结果的分析，依据射流的紊动特性，将波浪环境中紊动射流的发展分为三个阶段，分析、总结了波浪环境中射流的紊动量在横剖面上的分布规律，及其在紊动射流三个不同发展阶段随波高的变化规律，并指出波浪环境下射流的紊动扩散量值大小约是对流的1／8～1／3，紊动扩散的作用不可忽略。本文基于对横流环境中窄缝射流的数值模拟结果，分析、总结了横流环境中不同射流比下各种喷角对涡心点、分离点位置以及稀释度的影响规律。提出“面积湍动能”的概念，并通过分析喷角对“面积湍动能”的影响规律，得出喷角为90度时最有利于射流水体与环境水体间掺混的结论。本文基于对波浪环境中窄缝射流的数值模拟结果，详细描述了波浪环境中的窄缝射流二维即时流场以及浓度场的特点，指出波浪环境中窄缝射流污染物的传播扩散过程分为三个阶段。通过对波浪环境中窄缝射流周期平均流场的分析，指出喷口轴线上周期平均的垂向速度衰减分为四个阶段，并总结了波高和波周期对波浪环境下窄缝射流的射流核长度、横剖面上射流垂向平均速度分布以及射流扩展率的影响规律。指出波浪影响射流特性的直接因素包括两个：第一，波浪水质点的最大水平速度；第二，波浪的摆动。波浪水质点的水平运动半径是影响垂向射流特性的根本因素，波浪水质点水平运动半径越大，波浪对射流特性的影响越显著。本文基于波浪环境中圆形射流的数值模拟结果，详细描述了波浪环境中的圆形射流三维即时流场以及浓度场的特点，着重对比了过喷口轴线顺浪向和垂直浪向的两个垂面上的即时流场、浓度场的差异，以及波浪环境中圆形射流过喷口轴线顺浪向垂面上浓度场与窄缝射流浓度场的差异。另外，通过对不同波要素、不同水平面上即时涡流场的分析，指出波浪环境中圆形射流水平面上出现的各旋涡结构中，肾形漩涡对出现频率最高。通过对波浪环境中圆形射流周期平均流场的分析，总结了波要素对三维圆形射流扩展率的影响规律，并着重对比了过喷口轴线顺浪向和垂直浪向的两个垂面上射流扩展率的差异，以及波浪环境中三维圆形射流与二维窄缝射流扩展率受波要素影响规律的差异。更多还原

【Abstract】 The key problem for renovating water environment is the control on the origin of pollution. One of the factors polluting water environment is just the out-of-order letting of cities’ polluted water. Because the cost of the waste water treated project is correspondingly cheap by letting the polluted water into rivers or sea, it has been the preferentially measure for dealing with polluted water of cities. Scientifically designing the mode of waste water letting and choosing the region of waste water letting all depend on the profoundly understanding for the polluted water’s hydrodynamic characteristics and the contamination’s diffusion, transport characteristics. Polluted water usually flows into rivers and sea by the mode of jet. Systemically making the basic study of the jet’s characteristics in the flowing ambient fluid not only proves the understanding on the turbulent flow, but also supplies more perfect academic base for the jet’s application in the production, so it has important scientific value and factual significance.This paper makes more systemically study on the jet’s characteristics in the flowing ambient fluid by the experiment and numerical simulation, including the jet’s flow state, expansion rate, and the distribution of concentration. In the experiment the time-averaged and turbulent characteristics of the vertical round jet in wave environment is studied by the wave flume and the system of particle image velocimetry (PIV); in the numerical simulation based on Reynolds time-averaged equations the turbulent jet’s 2D and 3D numerical modes are established by the stress-algebraic turbulent model and VOF method. Numerically simulate the plan jet and round jet in the flowing ambient environment, analyze the jet angle influence on the jet’s characteristics, and makes the systemically study on the plan and round jet’s characteristics in wave environment.Based the experimental results of the jet’s velocity field this paper summarizes the rules of the wave period influence on the length of potential core, the distribution of vertical velocity on the cross-profiles, and the jet’s expansion rate. By analyzing the jet’s turbulent characteristics the process of the turbulent jet in wave environment is divided into three phases. Summarize the rules of the distribution of turbulent terms on the cross-profiles and the change of turbulent terms with the wave height, and indicate that the value of the jet’s turbulent diffusion is about the 1/8-1/3 of the value of convection in wave environment, so the function of the diffusion can’t be ignored. Based the numerical simulated results of the jet in the cross flow this paper summarizes the rules of the jet angle influence on the position of the vortex center, separation point and dilution. The concept of "area turbulent kinetic energy" is proposed and by using this concept the relationship between mixing intensity and jet angles is analyzed. The results show that 90 degree jet angle is the most favorite condition for jet water mixing with environment water.Based the numerical simulated results of the plan jet in wave environment this paper describes the characteristics of the instantaneous velocity and concentration field, and indicates that the progress of the contamination’s spreading is divided into three phases. By analyzing the period-averaged velocity field of the plan jet in wave environment this paper divides the progress of the vertical period-averaged velocity falling on the axis of the spout into four phases, and summarizes the rules of the wave height and wave period influence on the length of potential core, the distribution of vertical velocity on the cross-profiles, and the plan jet’s expansion rate. The factors of the wave influence on the characteristics of the jet include: the first one is the horizontal maximum velocity of wave particle; the second one is the oscillatory wave motion. Based on the two reasons it can be conclude that the horizontal radius of wave particle motion is the essential factor affecting the characteristics of vertical jet, and the horizontal radius of wave particle motion is larger, the effect on the characteristics of vertical jet is more remarkable.Based the numerical simulated results of the round jet in wave environment this paper describes the 3D characteristics of the instantaneous velocity and concentration field, and emphasizes the contrast between the instantaneous velocities, concentration fields in the two vertical plans through the axis of the spout. In addition the conclusion is obtained that the pairs of kidney vortex has the highest frequency in all the vortexes in the horizontal plan by analyzing the vortex and velocity fields in the different cases. Summarize the rules of the wave terms influence on the rate of the 3D jet expansion by analyzing the period-averaged velocity field of the round jet in wave environment, and emphasizes the contrast between the rules of the wave terms influence on the rate of the 3D round jet expansion and the 2D plan jet expansion.更多还原