Experimental reduced-scale study on the resistance characteristics of the ventilation system of a utility tunnel under different pipeline layouts

With the rapid development of urban society, the advantages of utility tunnels are becoming increasingly prominent. As an important parameter of the ventilation system designed for use in a utility tunnel, the ventilation resistance coefficient is extremely important. An experiment device at a reduced scale was established according to a scale ratio of 5:1, and the scale relationship between the prototype and model was derived by applying the similarity theory. A cross–section with six different pipeline layout formations was tested under different air volume conditions, and the measured average wind-speed distribution and total pressure distribution data of each working condition were obtained. The experimental results under working conditions without a pipeline layout were compared with the calculation results of the empirical formulas for verification. The utility tunnel was divided into an inlet interval, outlet interval, and middle stable interval. The resistance characteristics along the tunnel and the local resistance characteristics at the inlet and outlet were analyzed under different working conditions, and the effects of the resistance coefficient on Reynolds number and the proportion of the pipeline area were analyzed through an ANOVA test. The results indicate that the resistance coefficient of the middle stable interval is significantly different based on the pipeline layout and air volume, whereas the inlet and outlet intervals are significantly different based only on the pipeline layout. A polynomial regression was used to obtain the fitting relation between the resistance coefficient, Reynolds number Re, and the proportion of the pipeline area ratio, the error of which was within 10%, thus providing a theoretical basis for the design and later optimization of a ventilation system.