Abstract: We use the numerical simulation method to study the pressure drop and flow characteristics of outdoor fire hydrant under different outlet switch states, and the flow characteristics of multiple fire hydrants with different spacing in the pipeline are calculated. The results show that the flow rate of about 19% of the fluid at the fire hydrant outlet is much lower than the average flow rate, which cannot be sprayed to the designated firefighting point; opening more than one switch will cause the pressure reduced by 58.3%~85.7%, and flow reduced by 28.3%~62.7%, which will harm the high- rise building firefighting and long distance firefighting; when multiple hydrants are opened, the flow of single fire hydrant is reduced by 13.5%~33.8%, and the total flow is reduced by 14.6%~27.0%; besides, with the increase of fire hydrant spacing from 10 m to 120 m, the flow of fire hydrants in the middle and lower reaches will be gradually reduced. The study can provide guidance for the installation and use of fire hydrants

Key words: fire hydrants, fire water supply, numerical simulation