NUMERICAL MODELING OF VENTILATION FLOW DISTRIBUTION IS SUBWAY TUNNELS WITH CONSIDERING OF THE PISTON EFFECT

Abstract

Metro is the main transport artery of modern megapolis and represented complicate  underground building construction. Because of its multifunctional load, leading industrial states are focused on the issue of arranging subway under modern construction standards. One of the main problem of metro construction and safe exploitation is to ensure the functioning of the ventilation system relevant to the increased safety norms. The influence of the piston effect on the dynamics of ventilation flows generated between metro stations, in the main part of scientific literature is described in the semi-empirical manner, is not characterized by high accuracy and inegatively affects on the underground design and construction works. The current level of computer technology develops the possibility of the dynamics of ventilation flows in the subway tunnels by more accuracy in terms of numerical modeling of the air flow. The paper discusses the problem of distribution of ventilation flows caused by the piston effect in metro tunnels, which give affects the determination of  ventilation parameters. The task was set for the conditions of  Tbilisi Metropolitan, with the following basic data: Tunnel length - 1200m; Cross section - 16 m², length of train 60 - 80 m; Train speed 6.0, 8.0,10.0, 12.0 m/s; Acceleration of the train – 1.0 m/s², the train cross section 4.00, 5.00, 6.25 m². The calculation was performed by the PYROSIM 2016 software. As a result of the simulation, was determined the variability of ventilation flow caused by the piston effect depending on the speed and cross section of the train and the geometry of the tunnel.