高剪切力下气泡聚并与破碎特性的数值研究

了解气泡在剪切力场中的聚并与破碎机理及生长与运动特性，对于气液搅拌槽中桨叶的优化设计具有重要意义。将欧拉-欧拉模型与群体平衡模型(population balance model, PBM)进行耦合，对不同剪切力下的气液两相流场进行求解，研究了剪切力、高剪切力下进气速度、气泡塔高度对气泡聚并与破碎的影响，并结合气泡的聚并与破碎模型对高剪切力下气泡的聚并与破碎机理进行了探究。研究表明，剪切力主要影响气泡的破碎，当剪切力较小时其对气泡破碎的影响较小，随着剪切力的增大其对气泡破碎的影响逐渐显著，使小气泡的含量大幅增多；高剪切力下进气速度、气泡塔高度对气泡的聚并与破碎的影响不明显。

Numerical study of bubble coalescence and breakup characteristics under high shear force

It is of great significance to understand the coalescence and breakup mechanism of bubbles as well as their growth and motion characteristics in the shear field for the optimal design of blades in a gas-liquid stirred tank. Under different shear forces, gas-liquid bi-phase flow field was obtained by coupling Eulerian-Eulerian model with population balance model (PBM). Influence of shear force, intake gas velocity under high shear force and bubble tower height on the coalescence and breakup of bubbles was studied. Combining with bubble coalescence and breakup model, the coalescence and break mechanism of bubbles under high shear force was revealed. Results show that the shear force dominated the breakup of bubbles. Small shear force had little effect on the breakup of bubbles. The increase of shear force enhanced the breakup of bubbles with the significant increase of small bubbles fraction. Effect of intake gas velocity and tower height on the coalescence and breakup of bubbles was not obvious under high shear force.