Simulation Of Gas Micro-flow Field In Goaf Under U-type Ventilation

In this paper,the author uses the theory of dynamics of fluids in porous media,advanced seepage mechanics and computational fluid dynamics to have an investigation on the gas micro-flow in goaf under the dynamic ventilation of U type working area.In this paper,the method of similarity simulation and numerical simulation are used to study the gas micro-flow in goaf.The author uses the similar simulation materials to make the experiment of air flows in porous media area,and obtain the flow characteristics of the material filled in the different diameter square tube,which provide the theoretical basis for the experiment of goaf flow field.Experiments were carried out on goaf flow field and the experimental results show that:(1)The flow law of tracer gas is first flow into the inlet side of the goaf by the working area,and then flow into the outlet side,and finally gathered in the deep part of the goaf;(2)There is a jet inertia effect in the inlet side of the goaf,which causes the tracer gas to accumulate in the deep part of the goaf,and at the outlet side,the air flow have a stripping effect on the tracer gas,which keep the gas concentration at a low level.The author establishes the physical model as the same size as the goaf,which based on the prototype of the experimental platform for goaf flow field,dose numerical simulation by using software of fluent,obtains distribution of tracer gas concentration,gas velocity distribution and static pressure distribution.The results show that the distribution of tracer gas concentration in numerical simulation is consistent with that of the simulated gas concentration in the simulation experiment of the goaf,which validates the accuracy of similar simulation experiment.The study aimed at investigating the effect of changing pressure on the gas micro-flow of the goaf,produces the physical model of goaf based on mathematical model of the simulation experiment and actual goaf,simulates the gas micro-flow field under the pressure change by using software of fluent,obtains static pressure distribution,Streamline distribution,air leakage velocity distribution,gas concentration distribution and oxygen concentration distribution,analyzes the influence of changing pressure on micro-flow field,the spontaneous combustion "three zones",the gas hazard area and the oxygen concentration field.