【作者】 陈小明；

【导师】 尤学一；

【作者基本信息】 天津大学 ， 环境科学， 2004， 硕士

【摘要】 大气和海洋之间的气体交换是地球生物化学循环中的重要环节。近年来越来越受到人们的关注。另外,在其它领域如在环境工程和化学工程中,气液界面处气体传输问题也是非常重要的。作为气液界面传质研究的开始,本文首先建立了基于两相流理论的数值波浪水槽。本文中界面采用VOF法跟踪,流动控制方程为连续方程和N-S方程,入流边界采用推板式造波,在出流边界之前设置人工衰减层消波,从而出流边界可设为无滑移墙壁。控制方程采用有限体积法离散,计算网格采用不均匀的矩形网格。通过与理论值比较波形和某点处压力、速度随时间的变化,验证了本文建立的数值波浪水槽的正确性。在此基础上,研究了人工衰减层中吸收强度的取值问题,发现吸收强度的最佳取值依赖于波长、水深和振幅。同时考虑了气相压力变化和粘性对波浪场的影响,得到这两个因素均对波浪场没有显著的影响。最后,又对平面泊肃叶流中小振幅扰动的空间演化进行了数值模拟。流动控制方程为N-S方程,入流边界为速度入口,开边界为出流边界(outflow),计算时将小振幅的Tollmien-Schlichting (TS)波叠加在泊肃叶流上产生扰动,观察小扰动的空间发展。计算结果与Orr-Sommerfeld方程结果符合很好。更多还原

【Abstract】 For the global biogeochemical cycles, gas exchange is one important linkbetween the atmosphere and the ocean. Thus, in Recently, the gas exchange betweenthe atmosphere and the ocean has received much attention. Air-water gas transfer isalso very important in other areas, such as environmental engineering and chemicalengineering. As the first step of studying the gas transfer on the interfacial surface, anumerical wave tank is built in this dissertation.In this numerical wave tank, the two-phase flow theory is firstly introduced tomodel the behavior of water and air. The interface is tracked by VOF method. Thewave is introduced by an oscillating plane and before the outlet boundary, a artificialdamping layer is presented to absorb the reflection wave. Thecontrol-volume-based technique is used to convert the governing equations toalgebraic equations that can be solved numerically. The non-uniform rectangle gridsare arranged according to requirements, such as finer grids at air-water interface.The outlet pressure condition is used at the top boundary. By comparing the theorywith wave profile and the time-depending pressure and velocity at a certain point,the correctness of our numerical wave tank is proved. Numerical results show theabsorb intensity is mainly depend on the amplitude and length of wave and the depthof water. The effects of the air pressure and air and water viscous on the water waveare studied. It is found that the above factors have little influence on water wave.The spatial development of disturbances in plane Poiseuille flow is simulatednumerically. The controlling equations are N-S equations. The mean velocity profileis at the inlet boundary and the outflow is used at the outlet boundary. ATollmien-schlichting (TS) wave with small amplitude known from Orr-Sommerfeldequation is superimposed on the mean flow field to introduce a small disturbance.Numerical results show that the spatial development of disturbance is in a goodagreement with that of Orr-Sommerfeld equation.更多还原