A hybrid discrete bubble-lattice Boltzmann–discrete element model for gas-charged sediments

Abstract

This paper presents a hybrid discrete bubble-lattice Boltzmann-discrete element modelling framework for simulating gas-charged sediments, especially in the seabed. A discrete bubble model proposed in chemical engineering is adapted in the coupled discrete element/lattice Boltzmann method to model the migration of gas bubbles in saturated sediments involving interactions between gas bubbles and fluid/solid phases. Surface tension is introduced into the discrete bubble model in this work, so that it can handle the complex gas-fluid-solid interface. The discrete element and lattice Boltzmann methods are, respectively, employed to simulate fluid flows and mechanical behaviours of sediments. A velocity-interpolation based immerse boundary method is utilised to resolve the coupling between the fluid flow and the solid/gas phase. The proposed technique is preliminarily validated using simulations of bubble migration in fluids, which is followed by high-resolution investigations of the transport of a gas bubble in seabed sediments. It is demonstrated that this hybrid method can reproduce, to a certain degree, the characters of bubbles moving in seabed sediment tests.

Study on the Micro-Mechanical Mechanism of Fine-Grained Marine Sediments Subjected to Shallow Gas Invasion

“…Mitchell and Choi et al [17] performed gas injection tests on two sediments with different particle sizes; using a combination of X-ray scanning technologies (CT), they confirmed for the first time that capillary invasion mainly occurs in the coarse-grain sediments, while fracturing invasion mainly occurs in the fine-grain sediments. Wang et al [18] captured the entire process of capillary and fracturing invasion by scanning the different gas injection phases with a high-precision industrial CT. As shown in Figure 2, red area represents soil mass, while blue area represents gas bubbles. In the case of capillary invasion, the bubbles appeared to be diffused, while in the case of fracturing invasion, the cracks develop diagonally upward along the bubble surface.…”