Performance evaluation of alternative tunnel longitudinal ventilation systems using two inclined jets

• Hydrodynamic characteristics of twin inclined jets were studied analytically and numerically.
• Effects of jets inclination and the confinement ratio on the installation efficiency were examined.
• Results show that there exist an optimal pitch angle and an optimal confinement ratio that enhance air induction.
• The mono-dimensional model has been demonstrated to be accurate when compared to CFD numerical results.

This paper advances a novel design for providing longitudinal ventilation which utilizes the principle of induction while ensuring energy efficiency and allowing a better use of space. The induced longitudinal flow is generated by two inclined jets located about the midpoint between the floor and the ceiling allowing jets to entrain stagnant air freely necessary to guarantee the longitudinal air flux in tunnel. A mono-dimensional model and a CFD model have been developed in a parametric study to investigate the influence of inclination and the effect of confinement on the installation efficiency. It was found that by controlling the pitch angle of the two jets, the induction effect and then the installation efficiency are enhanced in order to achieve a successful use of the new ventilation system. Results show also that there exists an optimal confinement ratio assuring a better use of the longitudinal systems by producing the maximum induced air flow rate.