Numerical investigation on effect of air vent on air supply

Abstract

An improper design of an air vent will not only cause waste of resources but also seriously threaten the safety of the spillway tunnel. The present study analyzes the effects of the area and position of the air vent on the air supply, using the volume of fluid method with the k–ε turbulence model. The air speed in the air vent will decrease with an increase in the area, but the quantity of air supplied will increase. When the area of air vents is equal to the tunnel residual, the air supply capacity of the air vent reaches the maximum. A relationship between the quantity of air supplied and the area of the air vent is put forward, and the error with the prototype observation result is about 10%. The distribution of negative pressure in the tunnel may be improved by arranging the air vent in a proper position; the quantity of air supplied also decreases as the distance between the air vent and the pressurized conduit increases. In general, it is more advantageous to position the air vent upstream. These results provide a reference for the air ventilation design in hydraulic engineering.