DESIGN OF SUITABLE VENTILATION SYSTEM FOR A LONG HIGHWAY TUNNEL USING CFD

Abstract

Ventilation system plays a fundamental role in the operation of tunnel. All road tunnels require ventilation, which can be provided by natural means, traffic induced piston effect and mechanical ventilation equipment. Ventilation- system prevents the pollutants from exceeding predetermined levels, maintains specified values for temperature, humidity, methane, diesel fumes, and dust in all sections of the running tunnels, controls or extracts smoke to allow fast and safe firefighting activities. Ventilation systems can be analyzed by the use of commercially available• CFD codes like Fluent, Ansys, Phoenics etc. The CFD analysis of flow field in a long highway tunnel was done by constructing the geometry modeling and meshing in the ANSYS ICEM CFD commercial code. The ANSYS CFX code is used for the simulation of pollutants dispersion in the highway tunnel. Three-dimensional turbulent flow and dispersion of gaseous pollutants, carbon monoxide (CO) and nitrogen oxides (NO,) in a road tunnel were modeled using the standard k-E turbulence model. Vehicle emissions were estimated from the measured traffic flow rates and modeled as sources along the tunnel floor.