Empirical and numerical investigation on the optimal length of eddy airflow in dead-end tunnel

This paper uses vortex flow modelling to find the optimal length of eddy airflow in dead-end gallery using air velocity, pressure and diesel particulate matter (DPM) simulations and field investigations. Computational fluid dynamics (CFD) modelling conducted for four different dead-end crosscut lengths (10 m, 15 m, 20 m, and 25 m), three different crosscut angles (45^o, 90^o and 135^o) and different air velocities in adjacent galleries revealed that a distinct vortex flow develops in the dead-end crosscut. Results indicated that an eddy airflow revolved in a curved form, while the air velocity and pressure decreased towards the centre of the vortex and DPM concentration increased towards the centre of the vortex. The eddy airflow influence distance in a dead-end crosscut depends on the crosscut angle and air velocity in the adjacent gallery. If the air velocity in the adjacent gallery is one m/s and the crosscut angle is 90^o, eddy airflow ventilates up to 20 m from the entrance. Though the air velocity in the adjacent gallery is 4 m/s, eddy airflow is not ventilating the crosscut after 30 m from the crosscut entrance. The eddy flow distance is lower in obtuse-angled crosscuts than the acute-angled crosscuts.