Numerical simulation of bubbly flows by the improved lattice Boltzmann method for incompressible two-phase flows. (30th March 2023)

• Record Type: Journal Article
• Authors: Saito, Satoshi; Yoshino, Masato; Suzuki, Kosuke
• Is Part Of: Computers & fluids. Volume 254(2023)
• Publication Date: 2023-03-30
• Subjects: Lattice Boltzmann method -- Bubbly flows -- Cahn–Hilliard equation -- Conservative Allen–Cahn equation -- Slug flow -- Churn flow; Fluid dynamics -- Data processing -- Periodicals; 532.050285
• DOI: 10.1016/j.compfluid.2023.105797
• Languages: English
• ISSNs: 0045-7930

Abstract

Abstract: Bubbly flow problems are simulated to verify the effectiveness of the improved lattice Boltzmann method for incompressible two-phase flows. In this method, it is possible to compute two-phase fluid flows with high density ratios accurately and efficiently compared with the previous method. Firstly, we simulate a stationary bubble to investigate the accuracy of the interfacial tension. As a result, the calculated pressure differences are in good agreement with the theoretical predictions, and the relative errors of the pressure difference are less than 5%. Secondly, we simulate a single bubble rising in a liquid under gravity. It is found that the terminal bubble shapes and Reynolds numbers are in good agreement with available numerical and experimental data. Thirdly, we simulate two bubbles rising in a liquid under gravity for different initial arrangements. It is found that the bubble shapes and transient Reynolds numbers during the coalescence process are generally in agreement with the available numerical results. Finally, we simulate typical slug and churn flows in a square duct. It is found that transition from slug flow to churn flow occurs when the pressure difference between inlet and outlet of the duct is increased. In addition, it is found that square ducts with larger width tend to generate churn flows. These results demonstrate that the present method is applicable to complicated bubbly flow problems. Highlights: Bubbly flows are simulated to verify the effectiveness of the improved two-phase LBM. A stationary bubble in a liquid is calculated to check the interfacial tension. Behaviors of a single bubble and two bubbles rising in a square duct are examined. Slug and churn flows are stably simulated under gravity and a pressure difference. The results show the present numerical method can be applied to complex bubbly flows.