Coupled Fluid-Structure Model for Duckbill Valve Flow

DuckBill Valves (DBV) are non-return axial water flow valves made of a fabric reinforced layered rubber material, and are widely used for large pipe diameter flows with low back pressures. Fluid-Structure Interaction (FSI) is directly involved in the opening process of the DBV, with the opening depending on the pressure differential across the valve. This paper presents an FSI simulation of the DBV opening process by using a Finite Element Method (FEM). The valve is modeled as a laminated thick shell structure with some simplifications to the boundary conditions. The pressure load acting on the shell surface of DBV is a function of the variable valve cross-section area and determined, for preliminary analysis purposes, by using a simple potential flow model for the fluid mechanics. The hyperelasticity of the rubber and orthotropy of the fiber reinforcement, as well as large deflections of DBV, are considered in the simulation. The valve is modeled as being closed when the upstream pressure is applied and the transient opening process is tracked until a steady state opening is achieved. A static case of viscous flow passing through the deformed valve structure has also been carried out to compare the pressure and velocity fields of fluid flow with the corresponding pressure and velocity distribution predicted by the potential flow FSI model in order to evaluate the influence of fully viscous flow in the FSI model in future work. More realistic modeling of the edges of the valve where thick shell elements are considered inappropriate is also discussed.