【作者】 马斗；

【导师】 刘明言；

【作者基本信息】 天津大学 ， 化学工程， 2009， 硕士

【摘要】 本论文综述了气液两相流的基础理论和数值模拟现状,建立了计算的物理模型和数学模型及相应的初始和边界条件,运用计算流体力学方法并结合实验对气液两相流中的单孔气泡形成、上升、变形和聚并等动力学行为进行了研究。基于欧拉-欧拉(Euler-Euler)观点,将气液两相处理成连续介质,对气泡在两相流中的运动过程建立了VOF模型,追踪气液两相之间的运动界面,并以Fluent6.3为平台进行了数值模拟研究。单气泡的上升变形过程模拟结果表明:气泡并不是呈直线上升运动,数值模拟结果与采用高速摄像法获得的实验结果进行了比较,一致性较好。且气泡越小,变形幅度越小,摆动幅度越大;模拟研究了液体黏度、表面张力对气泡上升、变形过程的影响,结果发现,液体黏度和表面张力增加,不利于气泡的变形。重点模拟研究了表面张力、液体黏度、液体密度、表观液速和孔口气速对气泡脱离时间和气泡平均直径的影响,结果表明,气泡脱离时间随表面张力和液体黏度的增大而延迟,随着液体密度、孔口气速和表观液速的增加而提前;气泡平均直径随着表面张力和孔口气速的增大而增大,随着液体密度和表观液速的增加而减小,随液体黏度变化的趋势不明显。对气泡的聚并过程进行了模拟,结果表明,气泡聚并过程分为三个步骤:靠近、融合和聚并;并从开始聚并时间的角度分析了表面张力、液体黏度和表观液速对气泡聚并的影响,表明:开始聚并时间随着表面张力和表观液速的增加而增大,随孔口气速的增加而减小,随黏度变化不明显;表面张力和表观液速的增大不利于气泡聚并,而孔口气速的增大有利于气泡聚并,液体黏度对聚并现象的影响不明显。更多还原

【Abstract】 On the basis of the overview of fundamental theory and simulation progress of the gas-liquid two phase flow, the physical and mathematical models for single gas bubble hydrodynamics are built and related parameters are determined in this thesis, and the formation, rising, deformation and coalescence of gas bubbles are studied by computational fluid dynamics and experimental methods.Volume of fluid (VOF) model is established to simulate the rising of gas bubbles in gas-liquid flow on the frame of the Euler-Euler point of view, in which the gas phase and liquid phase are regarded as continuum and the moving interface between two phases is tracked. It is concluded that bubble movement is not in a straight line. A better consistency is obtained, compared with the experimental results, which is obtained with high-speed camera technology. And the smaller bubble is, the smaller deformation and the larger swing amplitude is. The influence of liquid viscosity and surface tension force on bubble motion is investigated. It is difficult to deform with the increase of viscosity and surface tension force.The influence of surface tension force, liquid viscosity, liquid density, gas velocity and superficial liquid velocity on detachment time and bubble mean diameter is mainly studied. It is obtained that the detachment time of bubbles increases with the increase of the surface tension force and viscosity and the decrease of liquid density, gas velocity and superficial liquid velocity. As surface tension force and gas velocity increases and superficial liquid velocity and density decreases, bubble mean diameter increases. It is not obvious with the change of viscosity.The process of bubble coalescence is simulated and three steps are divided: close, integration and coalescence. The effect of all kinds of parameters on bubble coalescence is analyzed. With the increase of surface tension force and superficial liquid velocity, the beginning time of bubble coalescence increases accordingly. The beginning time of bubble coalescence increases with the decrease of gas velocity. The increase of gas velocity is beneficial to coalescence while the increase of surface tension force and superficial liquid velocity are not conducive to bubble coalescence. The effect of liquid viscosity on bubble coalescence is insignificant.更多还原