摘要

In a cross connection control field, the backflow assemblies that consist of an independently operated spring loaded check valve is an important device to prevent contaminations from reverse flow. In this paper, the interaction of a viscous fluid with a backflow preventer is investigated by solving Navier-Stokes equations and equilibrium equation for both fluid and solid. Three mesh systems are computed and compared to check grid independence and to obtain more reliable numerical results. The variables including displacement, velocity, and acceleration are presented as a function of time to describe the moving solid element. Whereas, the velocity vectors, pressure surface distributions, and pressure loss coefficients versus time are shown to reveal the resulting flow fields. The computational results show that the solid element will return to its static equilibrium position due to the effect of spring force and the development of a relatively stronger eddy at the upper right part of a solid body. The moving behavior of the solid body may cause a damage of the entire solid system and decrease the flow rate after a long-time action. This may imply that a block system is a better choice than a thin plate system for this type of backflow preventer, as the former one is balanced by fluid force at a new position to provide maximum flow rate if necessary.