Three-dimensional mesoscopic numerical simulation of the rising behavior of bubbles with large density ratio in porous media channels

In this paper, a three-dimensional numerical simulation of the motion behavior of bubbles in complex porous medium channels in a large density ratio gas-liquid system is conducted based on the lattice Boltzmann method. The Eötvös number (<i>Eo</i>), contact angle (<i>θ</i>) and Reynolds number (<i>Re</i>) are systematically discussed with emphasis on the law of their coupling effect affecting bubble velocity, morphological evolution and stagnation phenomenon. The results show that the increase of contact angle will reduce the bubble velocity but intensify the velocity fluctuations, making the bubbles tend flat, while the increase of <i>Eo</i> number significantly suppresses the influence of the contact angle, stabilizes the bubble velocity, and makes its shape close to a bullet head shape. When the contact angle is large (<i>θ</i> > 90°) and the <i>Eo</i> number is small (<i>Eo</i> < 10), the adhesion force is significantly enhanced and the bubbles will stagnate inside the porous medium. <i>Re</i> number and contact angle compete in the generation of resistance, and have mutually reinforcing effects on the average velocity of bubbles and interface evolution. The larger contact angle makes the deformation of the bubble tail intensify and becomes unstable, and as the <i>Re</i> number further increases, the tail tentacles are more likely to break, forming residual bubbles. It is also found in this work that the coupling between <i>Eo</i> number and <i>Re</i> number significantly affects bubble behavior in motion and morphological evolution. Under the conditions of high <i>Eo</i> number (<i>Eo</i> ≥ 25) and high <i>Re</i> number (<i>Re</i> ≥14), the bubble velocity increases with the <i>Eo</i> number rising, and the trend becomes more significant as the <i>Re</i> number increases; while under the conditions of low <i>Eo</i> number (<i>Eo</i> < 25) and low <i>Re</i> number (<i>Re</i> < 14), the speed change pattern is completely opposite. This phenomenon is due to the high instability of bubble morphology under the conditions of high <i>Eo</i> number and high <i>Re</i> number, which affects the buoyancy and speed performance. The research results provide important guidance for optimizing the flow behavior of bubbles in porous medium.