The CFD-DEM Coupling Analysis Of Submarine Landslides Induced By Natural Gas Hydrate Exploitation

The energy issue is a hot issue faced by the whole world.With the rapid development of deep sea exploration technology,natural gas hydrate is a new energy source with clean and efficient characteristics.Its identification,mining,transportation and storage are also focused on by domestic and foreign scholars.Natural gas hydrates are closely related to the formation of submarine landslides.It is of great practical significance to explore the natural gas hydrate layer and explore its intrinsic relationship with the triggering of submarine landslides.Therefore,this paper mainly discusses the impact of exploring natural gas hydrate to the structure of seabed rock and the interaction and influence between water and geotechnical particles after the formation of submarine landslides.The interaction between natural gas hydrates,sedimentary strata and oceanic waters is a problem in the field of fluid-solid coupling.In order to study at computational level,this paper uses computational fluid dynamics(CFD)and discrete element method(DEM)coupling(CFD-DEM)method: DEM is used to calculate the contact and force between particles of natural gas hydrate and sedimentary rock soil;CFD is used to figure out the fluid field and its movement state.These two methods build the coupling relationship,which makes the position and velocity information of particles continuously updated and transmitted to the fluid field as the calculation boundary.At the same time,the fluid field transfers the calculated buoyancy,drag force,etc.to particles.This paper uses the open source software to develop the advantages of source code,and choose CFD open source software Open FOAM and DEM open source software LIGGGHTS to realize CFD-DEM fluid-solid coupling calculation.On this basis,the paper links the commercial software PFC and CFDEM.PFC is used to finish the pre-processing to generate dense stacked particles,and then transports the particles into CFDEM for different working conditions.Paraview is also used for post-processing to realize open source software.Thus,open source software and non-open source software coupling computation is built.In order to verify the feasibility of developing the fluid-solid coupling calculation module in this paper,the stacking collapse experiment under different aspect ratios is firstly selected for calculation and simulation,and the calculation results are compared with previous model tests and similar simulations.From the aspects of the velocity and the motion process of the solid particles,and the fluid's velocity and disturbance state,the system analysis is consistent with the results of the model test,similar simulation,and the actual situation,which fully explains the correctness of the calculation module.In order to investigate the influence of natural gas hydrate mining on the stability of submarine landslide,the different slope angle deposits containing natural gas hydrate layer are firstly calculated and simulated in the marine environment to figure out the critical slope angle.Mining the natural gas layer to simulate the physical truth,comparing the macroscopic structural changes of ocean rock and soil under different excavation sizes and calculating the particle velocity,force and fluid field velocity's changing process can conclude the influence law of natural gas hydrate mining on the stability of submarine landslide.