Qin Lou's scientific contributions

The miscible displacement with fluid-solid dissolution reaction in porous media is a typical process in many industrial applications, such as underground-water pollution decontamination, oil recovery or geological sequestration of carbon dioxide, etc. It is a significant problem in engineering and physics applications. It can be known that the dissolution reaction can change the structure of the porous media, which will have a great influence on the miscible displacement process. However, the relationship between the displacement process and the dissolution reaction in porous media is not fully studied. In this paper, the miscible displacement with dissolution in the porous media is simulated by a lattice Boltzmann method (LBM). The study focuses on the influence of the internal structure change in the displacement process, and further quantitatively analyzes the changes of the porosity and displacement efficiency by changing the Damkohler number (Da) and the Pèlcet number (Pe). The results show that when Da is large enough, the dissolution reaction will generate a few wormholes in the porous media, and the displacement fluid will leave the porous medium along the wormholes, resulting in the decrease of the displacement efficiency. As Da increases, the reaction goes faster, the rate of change in porosity increases, the wormholes become wider, does yield a larger displacement efficiency. With the increase of Pe, the fingerings develop faster, the rate of change in porosity decreases, the displacement efficiency decreases.

Bubbles are existent everywhere and of great importance for the daily life and industry process, such as heat exchange rate influenced by bubbles in the tube, battery life partially decided by bubbles of chemical reaction in it, etc. With the further requirement for miniaturization, physical mechanisms behind bubble behaviors in microchannels become crucial. In the present work, the lattice Boltzmann method is used to investigate the behavior of bubbles as they rise in complex microchannels under the action of buoyancy. The channel is placed with two asymmetric obstacles on its left and right side. Initially, the lattice Boltzmann model is tested for its reliability and accuracy by Laplace law. Then a few parameters of flow field, i.e. the Eötvös number, the viscosity ratio, the vertical distance between the obstacles, the horizontal distance between the obstacles, are employed to study the characteristics of the bubble during the movement, including the deformation, the rising speed, the residual mass, and the time of bubble passing through the channel. The results are shown below. First, the trend of the bubble's velocity changing with time in the process of passing through the channel corresponds to the change process of the dynamic behavior of the interface, i.e. the bubble velocity decreases when the bubble shape changes significantly under the same channel width. Second, with the increase of \begin{document}$ Eo $\end{document} number, the bubble deformation as well as the bubble velocity increases and the bubble residual mass decreases. Besides, the gas-to-liquid viscosity ratio has a significant effect on the bubble velocity. Under the condition of high viscosity ratio, the bubble shape is difficult to maintain a round shape, while the bubble rise velocity increases and the residual mass of the bubble decreases with the viscosity ratio. What is more, when the obstacle setting is changed, the longer the vertical distance between the two asymmetric obstacles, the shorter the bubble passing time is, and the faster it will return to the original shape after passing through the obstacle, while the residual mass of the bubble shows a change trend of approximately unchanged-increase-decrease-increase with the augment of the vertical distance between the obstacles. In the study of changing the horizontal spacing, two cases: the two obstacles are changed at the same time (Case A) and only the one-sided obstacle is changed (Case B), are considered. The results show that under the same small horizontal interval, the obstruction effect caused by changing only the length of one side obstacle is stronger. Finally, the study shows that when the width of the right obstacle is long enough, although the width of the obstacle continues to increase, the passing time of the bubble increases slowly, and the position of the bubble leaving from the obstacle is always approximately the same.