An Investigation On The Characteristics Of Bubble Motion In Complex Channel With Lattice Boltzmann Method

The movement of bubbles in the liquid is the most typical phenomenon in two-phase flow. It has attracted the majority of scholars in computational fluid dynamics community due to the widely application in the chemical industry, environment and all aspects of life. Recently, the research on the two-phase flow is mostly confined to the conventional channel, while the research on the two-phase flow in complex channel is very limited. In practice, most of the gas-liquid flow is not present in a conventional pipe, so study on the characteristics of bubble motion in complex channel has great practical value.To simulate the two-phase flow, tracking interface is the key issue, especially for the flow with large density ratio. In Zheng-model the treatment of interface tracking is simple, clear, and easy to implement. Therefore, in this paper, the Zheng-model is employed to simulate the movement of the bubble in straight channel and complex channel, respectively. The paper is organized as follows.1. The lattice Boltzmann method and its procedure are conducted. The procedure is validated by simulating the example of Laplace’s law and two bubble mergers.2. For the cease with different interface thickness, the Laplace’s law is calculated to study the effect of the interface on the numerical results. It is found that the numerical solutions and theoretical solutions can be achieved agreement when the interface thickness value is high. Particularly, the thickness of interface is set at5and the procedure can meet the computational accuracy. Then the motion of single bubble and two bubbles side by side in straight channel is simulated respectively. The bubble deformation, velocity of the bubble and the flow distribution situation in the motion process is analyzed to study the motion characteristics. And the two-dimensional model is extended to three-dimensional model and a good simulation results is also obtained.3. The behavior of an air bubble rising through a quiescent liquid in a complex channel consisting three half-circle throats has been studied by the lattice Boltzmann method. The moving trajectory and velocity of the bubble during its rising process is investigated and the numerical results are in good agreement with the experimental data. In the three-dimensional numerical simulation, quality loss is unavoidable and the volume correction method on Zheng-model is proposed which has obvious physical meaning, does not require any empirical formula and experience factor, and is also very easy to implement. At last, good results are obtained on the basis of the volume correction.