Novel correlation to evaluate the pressure losses for different traffic jam conditions in road tunnel

The main aim of the present work is to provide a novel correlation between different traffic jam conditions (Filling Traffic Tunnel) in road tunnel and pressure losses, in order to calculate the thrust required to the jet fan to induce the needed ventilation. The correlation refers to a longitudinal ventilation system of impulsive fans placed in a road tunnel with a rectangular cross section. The data necessary to build the novel correlation here proposed were obtained by means of 3-D model that was validated experimentally in previous studies. To evaluate the influence on required ventilation thrust, several traffic jam conditions and different average air velocities were considered. The proposed correlation provides pressure losses as function of FTT and average air velocity in the tunnel. The pressure losses were evaluated as difference between the thrust required by the ventilation system in empty tunnel conditions and the thrust required in traffic jam condition. The mean percentage error of the novel correlation here proposed is about of 3% respect to CFD simulation results. Furthermore, a friction factor for different FTT was provided. It allows to evaluate the pressure losses due to the traffic jam as distributed ones with an error value about of 3%.