A dual-scale turbulence model for gas-liquid bubbly flows

• Published in: Chinese journal of chemical engineering 2015-11, Vol.23 (11), p.1737-1745
• Main Authors: Guan, Xiaoping, Li, Zhaoqi, Wang, Lijun, Li, Xi, Cheng, Youwei
• Format: Article
• Language: English
• Subjects: Bubble-induced turbulence; Bubbly flow; Dual-scale turbulence model; Shear-induced turbulence; Two-fluid model; 双尺度; 标准k-ε模型; 模型模拟; 气泡直径; 气液; 泡状流; 湍流模型; 输运方程
• ISSN: 1004-9541; 2210-321X
• DOI: 10.1016/j.cjche.2015.09.003

A dual-scale turbulence model is applied to simulate cocurrent upward gas-liquid bubbly flows and validated with available experimental data. In the model, liquid phase turbulence is split into shear-induced and bubble- induced turbulence. Single-phase standard k-e model is used to compute shear-induced turbulence and another transport equation is added to model bubble-induced turbulence. In the latter transport equation, energy loss due to interface drag is the production term, and the characteristic length of bubble-induced turbulence, simply the bubble diameter in this work, is introduced to model the dissipation term. The simulated results agree well with experimental data of the test cases and it is demonstrated that the proposed dual-scale turbulence model outperforms other models. Analysis of the predicted turbulence shows that the main part of turbulent kinetic en- ergy is the bubble-induced one while the shear-induced turbulent viscosity predominates within turbulent vis- cosity, especially at the pipe center. The underlying reason is the apparently different scales for the two kinds of turbulence production mechanisms： the shear-induced turbulence is on the scale of the whole pipe while the bubble-induced turbulence is on the scale of bubble diameter. Therefore, the model reflects the multi-scale phe- nomenon involved in gas-liquid bubbly flows.