Study of the applicability and optimal arrangement of alternative jet fans in curved road tunnel complexes

Abstract

Constructions of underground complex road networks or tunnel complexes all over the world are in the ascendant. However, very few countries have developed specific recommendations or standards for the ventilation design of these special underground traffic facilities. Therefore, ventilation strategies in curved road tunnels, which is the typical characteristic of tunnel complexes, were mainly concerned and investigated by ANSYS Fluent in this paper. Flow field, pressure-rise coefficient (PC) and wall shear stress (WSS) were mainly compared and analyzed. The results show that the PC of alternative jet fans present a desirable performance than traditional jet fans, either for improving flow field and PC or decreasing WSS. In addition, the wall shear stress in curved road tunnels was especially analyzed, and both the confined WSS and the impactive WSS were defined. Besides, the confined WSS dominates in tunnels with large radius and the impactive WSS dominates in tunnels with small radius. Tilting the outlet of jet fans toward the tunnel floor and the convex side of tunnels with an optimal angle can reduce the confined and impactive WSSes, respectively. Moreover, the highest PC will be obtained by reducing the two types of WSS simultaneously. Findings of this study can provide significant reference for the design of longitudinal ventilation systems in curved road tunnel complexes.