| The application of the longitudinal ventilation system for long highway tunnel will be possible by building ventilation shafts and interchange stations to divide traffic tunnels in shorter lengths. These ventilation shafts enable much of the polluted air to be replaced with fresh air at the supply jet, and interchange stations supplement flows in the same way as the ventilation shafts except the slightly polluted air flow from another tunnel. Due to the exhaust effect at the exhaust tunnel and blowing effect at the supply jet, it is necessary to control ventilation shafts and interchange stations to avoid by-pass and recirculation flows.; In the past decades, sufficient information has been accumulated on the piston effect of vehicles, friction effect, and thermal effect in the longitudinal ventilation system for one-dimensional computer model. However, little study has been found in the literature on a three-dimensional numerical simulation near ventilation shafts and interchange stations. A computational fluid dynamics (CFD) methods based on compressible hydrodynamic equations, energy and mass transfer equations by using the large eddy simulation (LES) approach of turbulent flows has been applied to simulate the ventilation shafts and interchange stations in the longitudinal ventilation system of long highway tunnel.; The three-dimensional numerical model is applied to three cases of tunnel ventilation system. First, the uni-direction traffic tunnel is simulated under three traffic conditions which are normal traffic condition, congested traffic condition without jet-fan operation, and congested traffic condition with jet-fan operation. Second, the simulations of the bi-direction traffic tunnel are carried out under two traffic conditions which include normal traffic condition and congested traffic condition with jet-fan operation. Third, the simulation of whole tunnel ventilation system which include twin-tube with three ventilation shafts and three interchange stations in each tube under uni-directional and normal traffic condition is carried out for both uni-direction traffic tunnels. Due to the trade-off between the accuracy of three-dimensional simulation and the costs of computer time, a numerical model combined one-dimensional and three-dimensional numerical simulation is applied to the whole tunnel. |
