ABSTRACT: One of the problems facing the underground tunnels is lacking enough fresh air for passengers inside the subway. Also, because of the friction of the train with the railways, high heat is generated. So, the use of computational fluid dynamics to
distribute the required fresh air flow at the lowest possible cost is critical for the tunnels. In this research, Computational Fluid Dynamics (CFD) is used to perform 3D modelling and simulation for the tunnel of Cairo Metro Line No. 3. The standard k-e
turbulence model was used in the CFD analysis to simulate the ventilation airflow in a 1075m tunnel length. The simulation reveals that the tunnel airflow rate induced by the speed of the fan is more desirable. Also, the addition of a jet fan causes an eddy current that improving the efficiency of tunnel ventilation, thereby greatly reducing ventilation time, and increasing
efficiency in cases where the diameter of the tunnel equals 15 m, the speed of the fan is 1480 r.p.m, and the air flow rate is 80-
120 m3/s. This led to improve fan speed efficiency and airflow distribution in the tunnel. Similar way of simulation is used for
road tunnel ventilation.