Simulation Of Air And Water Flow In A Dentation Fracture Based On Lattice Boltzmann Method

Airflow and water flow in fracture media is an important natural process for geological resources and energy development.In the microstructure,the rough structure of the fissure will affect the fluid flow,but it is difficult to analyze the issues like how the complex shape of the fissure affects the flow of groundwater,whether the crack of the same shape has the same effect on different fluid flows,is the Darcy law generally accepted by the academic community applicable and so on only by experimental methods.In order to overcome this difficulty,the lattice Boltzmann numerical simulation method is adopted in this paper,and the dentate crack is selected as the representative of the rough crack to simulate the flow of air and water.The model size ratio has been changed to explore the general law of toothed micro-cracks.When using traditional microscopic methods to simulate the problem of dentate fissure seepage,it is necessary to construct large-scale linear equations,which is very difficult to calculate,and the application of these traditional methods can not show the internal details of the microfluid.The lattice Boltzmann method has the characteristics of simple implementation process,convenient boundary processing and good parallelism,and has good applicability for simulating fluid seepage.In this paper,the model of different physical model sizes and different groove ratios is simulated by airflow and water flow.The collision flow migration process by lattice Boltzmann method is used to calculate the flow rate under steady state,and the flow line distribution and flow relationship under different pressure differences are obtained..The lattice Boltzmann method can clearly show the fluid flow and velocity distribution,which can effectively compare and analyze the fracture flow results of different models.The simulation results show that clockwise eddy currents develop in the fracture and have an effect on the flow velocity distribution.Compared to the water flow,the airflow vortex has a faster rotation speed,a higher center point,and a longer top slope.When the model size is reduced,the airflow and the water flow show a similar law;when the length of the groove portion of the model becomes longer,the vortex change in the flow field is more obvious as the pressure difference increases,and the vortex of the water flow changes slowly.In different models,the flow through the fracture section increases with the increase of the pressure difference,and the airflow is nonlinear,which does not satisfy the Darcy flow hypothesis,and the water flow is linear,satisfying the Darcy flow hypothesis.The reason for the inconsistency between the two fluids is that the viscosity coefficient of the fluid is relatively large,and the viscosity coefficient is relatively small,so that the velocity of the gas flow is a hundred times that of the water flow.As the pressure difference increases,the vortex also increases significantly,resulting in a straight channel.The flow rate of the traffic has slowed down,so it shows a phenomenon of non-Darcy flow.The method used in this paper can be further applied to the simulation of fracture flow in other different forms.