通流截面积的突变对添加剂水溶液管流减阻效果的影响及其机理

项目名称： 通流截面积的突变对添加剂水溶液管流减阻效果的影响及其机理

项目编号： No.51476051

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 能源与动力工程

项目作者： 蔡书鹏

作者单位： 湖南工业大学

项目金额： 82万元

中文摘要： 添加剂减阻技术已在欧美日的水循环输送系统得到了实际应用，取得了显著的经济效益。此领域的研究大多仅限于管内充分发展紊流的减阻，而水循环管网中的阀门、突扩及突缩等通流截面积突变形成的扰动会使很多区段的流动处于发展中，进而必使减阻特性依存于剪切强弱的减阻流的减阻率及流动结构发生改变。本项目在充分发展的减阻管流中安放不同内径的矩形横截面圆环或改变上下游管径，物理模拟实际水输送管网中的不同通流截面积突变的流动条件。在通过下游沿程压差测试揭示通流截面积突变对下游减阻率影响规律的基础上，采用流场染色可视化技术察明减阻剂对扰动流团抑制的时空演化特征、对扰动和管壁耦合作用下紊流猝发的抑制规律；通过LDV流场测试探究,受扰动的下游减阻流由主流向时均速度、主流向及横向速度脉动强度以及雷诺剪切应力的断面分布所表征的流动结构的发展特性及层流向紊流延迟转捩的过程；通过两静压孔的静压时域波形，揭示下游所形成的紊流泡囊或紊流塞的数量生成强度和随流动的生长速度被抑制的规律。本项目对进一步直接阐明表面活性剂减阻的动力学机理及合理设计表面活性剂减阻水循环系统具有重要的理论和经济意意义。

中文关键词： 层流；流态转捩；局部扰动；流动结构；紊流塞

英文摘要： The additive drag reducing technology has been successfully applied to the regional water-transporting systems in European and American countries and Japan. It should be noted that so far most drag-reducing studies have mainly focused on a fully developed turbulent pipe flow. But, a water-transporting pipeline network is necessarily with valves and locally sudden alternations in pipe diameter,which certainly will affect the drag-reducing efficiency and flow structure in an additive drag-reducing pipe flow with making flow developing, because its drag-reducing behavior is dependent on shear stresses. In the present project,in an additive drag-reducing pipe folw with ring-shaped roughness elements at the middle and an additive drag-reducing pipe flow with a locally sudden alternation in pipe inner diameter, the influence of sudden changes in flow area on the additive drag-reducing behavior on the downstream from the location where the flow area is sudeenly altered is firstly revealed. The time-space evolvement of depressing of additives on the disturbed flow regions and turbulent burst events induced by coupling the disturbance with the pipe innre-wall is examined by visualizing the disturbed flow field with dye. The developing characteristics of flow structures along with the pipe axis is also clarified and it is revealed how the transition to turbulent flow is delayed by using a laser Doppler velocimetry. Moreover,it is investigated how generation and growth of turbulent puffs and slugs in the initial stage of the transitional flow is suppressed by additives, through the pressure time-evolution acquired by two pressure taps. The project has important scientific and economic value for further revealing directly the additive drag-reducing mechanism and designing an additive drag-reducing water-circulating pipeline system with higher drag reduction.

英文关键词： Laminar flow;flow pattern transition;local disturbance;flow structure;turbulent slug