Abstract:

The Eulerian-Lagrangian method has been widely used to simulate the flow pattern, bubble size (or gas holdup) and its distribution in gas-liquid reactors. However, this method reported in literature is mainly based on the critical Weber number viewpoint to describe the bubble breaking behavior, and the size of the broken sub-bubbles is determined by random numbers. The existing experimental and theoretical studies have shown that the viewpoint of critical Weber number cannot reflect the influence of physical parameters (e.g. gas density) such as gas density and gas redistribution within the bubble on bubble breakup behavior. In view of above shortcomings, this paper proposes a new bubble breakup model suitable for the Eulerian-Lagrangian framework that considers the contribution of gas redistribution mechanism, and develops a solver based on this new model on the basis of open-source software OpenFOAM. The model predictions are in good agreement with the measured time-averaged axial liquid velocity and bubble size distributions. Particularly, the proposed model considering gas redistribution mechanism successfully predicts the bimodal distribution characteristic of bubble size distribution observed in the experiments.

Key words: Eulerian-Lagrangian method, mathematical modeling, bubble column, bubble, breakup, coalescence

摘要：

欧拉-拉格朗日方法已被广泛应用于模拟鼓泡塔等气-液反应器内的流型、气泡尺寸（或气含率）及其分布。文献中该方法主要基于临界Weber数观点来描述气泡破碎行为，且破碎后的子气泡尺寸由随机数确定。但现有实验和理论研究表明，临界Weber数约束不能体现气体密度等物性参数和泡内气体重分布对气泡破碎行为的影响。针对这些不足，提出了适用欧拉-拉格朗日框架且考虑泡内气体重分布贡献的气泡破碎机理模型，并利用开源软件OpenFOAM开发了基于新破碎模型的求解器。新模型预测结果能较好地吻合实验测量的时均轴向液速、气泡尺寸及其分布等实验数据。特别地，考虑泡内气体重分布现象的破碎机理模型成功预测了实验观测的气泡尺寸双峰分布特征。

关键词: 欧拉-拉格朗日方法, 数学模拟, 鼓泡塔, 气泡, 破碎, 聚并