Swing Check Valve CFD: Pressure Drop and Flow at Every Disc Opening

A valve manufacturer wanted hard flow data for a large-bore swing check valve from its range. Its customers ask how much pressure the valve costs at different flow rates and how much it passes when the disc is only partly open, and many of them know CFD well enough to question the method behind any number.

Shirsh Technosolutions carried out the swing check valve CFD in ANSYS Fluent on the maker's own 3D assembly. We built a pressure drop curve across the working flow range and a flow curve across disc positions from a small opening up to fully open, and wrote up the method, mesh, turbulence model, boundary conditions and convergence evidence in a detailed report so the maker could put the results in front of its customers with confidence.

Geometry and flow volume. The maker supplied the valve assembly as a 3D model. We cleaned it up, extracted the internal flow volume through body, bonnet cavity, disc and hinge arm, and extended the inlet and outlet so the flow could develop before and after the valve. A separate flow volume was set up for each disc position, from a small opening in steps up to fully open.

Mesh. The volumes were meshed in Ansys Fluent meshing with a poly-hexcore mesh: hexahedral cells in the bore and polyhedral cells around the disc, hinge arm and seat, where the gaps are narrow and the gradients steep. Cell quality was checked on every model before solving.

CFD set-up in ANSYS Fluent.

• Three-dimensional, steady-state, incompressible turbulent flow of water.

• k-ω SST turbulence model, which handles the separation behind the disc and the recirculation in the bonnet cavity better than the standard k-ε family.

• Pressure-based coupled solver, second-order pressure and momentum discretisation.

• Two sets of boundary conditions. For the pressure drop curve, a velocity inlet stepped across the working range with a pressure outlet. For the opening sweep, a pressure inlet and pressure outlet holding a constant pressure difference, so the flow at each disc position could be compared on equal terms.

Results read for the maker. For every disc position we reported velocity contours on the central plane, velocity on the inlet and outlet faces and velocity profiles across both, along with 3D streamlines and vectors that show the jet under the disc and the swirl in the bonnet. The pressure drop was tabulated and plotted against flow rate, and flow rate and average inlet and outlet velocity were tabulated against disc opening. Residual histories were included to show each run had converged.

Common questions

What does CFD tell you about a swing check valve? It gives the pressure loss across the valve at any flow rate and shows how much flow passes when the disc is only partly open. The flow field also shows where the jet under the disc and the recirculation in the bonnet cavity sit, which helps when comparing body and disc shapes.

Why model several disc openings instead of only fully open? In service the disc of a swing check valve often hangs part way, especially at lower flows. Modelling a series of openings shows how flow capacity builds up with disc lift, which a single fully open result cannot.