Lattice Boltzmann simulation of the rising process of double bubbles in a microchannel with orifice plates

Based on the lattice Boltzmann two-phase large-density-ratio model, the rising process of double bubbles in a microchannel with orifice plates under the buoyancy force is simulated. The effects of the Eötvös number, relative size of bubbles, distance between bubbles, and distance between the top bubble and the orifice plate on the dynamics of bubble regrading the deformation and merge, as well as on the kinematics such as the rising velocity and the remaining bubble mass are systematically studied. It is found that as the Eövös number increases, the bubble deforms increasingly obvious when passing through the orifice. Moreover, the number and mass of bubbles entrained between the two bubbles also increase and the bubbles will contact, merge, and break several times during passing through the channel. The results also show that the time for bubbles to reach the top of the channel increases but the mass of bubbles passing through the orifice decreases as the Eötvös number increases. On the other hand, when the size of the upper bubble is larger than that of the lower bubble, there will be less entrained bubbles. As a result, the bubbles are slower to pass the channel but the mass of bubbles that can pass through the orifice plate increases. In addition, it is found that the entrainment of bubbles is not obvious if the distance between upper and lower bubbles is too large or too small, and the mass of bubbles passing through the orifice plate increases with the decrease of the distance between two bubbles and the distance between the upper bubble and the orifice plate.