Numerical simulation study on coal and gas outburst impact airflow

In order to reveal the propagation law of coal and gas outburst impact airflow, the distribution laws of velocity field, pressure field, impact force field, concentration field of impact airflow in the process of coal and gas outburst are simulated by using the high Mach flow and dense material transfer module in COMSOL software. The simulation results show that the impact airflow in the roadway is jet like, with a velocity of 378.6 m/s, and with the increase of distance, it presents a multi peak vibration attenuation trend. Periodic expansion wave zone and compression wave zone appear in the jet, and the tail of the jet zone develops into turbulence and instability, and moves disorderly in the roadway. The impact force of the protruding blast flow can be as high as 246.3 kPa, and the shock wave moves in the roadway at the local sound speed. The maximum gas diffusion distance is 133.6 m, and the gas volume fraction in the middle of the roadway is close to 100%. Due to the pressure difference in the roadway at the later stage of the outburst, the gas returns, and the high volume fraction gas is further mixed with the air in the roadway.