3D CFD SIMULATION OF AIRFLOW RE-DISTRIBUTION AND ASSOCIATED PRESSURE DROPS INSIDE THE OVERCAST IN UNDERGROUND COAL MINES

摘要

Overcasts are indispensible ventilation control devices to permit one airway to pass over another without mixing in room and pillar coal mining. The airflow distribution inside the overcast depends on its specific configuration at which the flow enters into it. This study uses 3D numerical simulation to examine the pressure and velocity distributions inside an overcast. The effects of the overcast angle on the flow field are also examined. The flow is assumed to be turbulent and isothermal and the standard k-ε model is utilized. Simulated results display flow separation and recirculation regions of different sizes occurring not only upstream and downstream from the overcast but also inside it. The results also show that the size of the recirculation regions increased with the increase in the angle before and after the overcast influencing significantly the flow field and pressure losses. The streamlines are plotted to show the 3D structure of the flow field. The results from the simulation can guide overcast design commonly used in underground coal mines.