OpenFOAM verification and validation : quantifying multiphase flow solvers for a u-bend simulation

This report presents a validation and verification study of multiphase solvers in the open-source software, OpenFOAM, for an open-channel U-Bend simulation. The study’s primary objective quantified the performance and discrepancies between different Volume of Fluid (VoF) solvers to establish robust guidelines for US Army Corps of Engineers (USACE) water resource applications. The study compared the algebraic solver, interFoam, with the geometric solver, interIsoFoam, and interIsoFoam’s various interface reconstruction schemes. Key parameters such as the Courant number, numerical schemes, and the effect of a buoyancy-modified turbulence model were evaluated for their effect on computational cost and solution accuracy. The results demonstrated that interFoam is significantly more computationally efficient than interIsoFoam, particularly at lower Courant numbers. While velocity fields were qualitatively similar across all solvers, interIsoFoam consistently predicted a lower free-surface elevation. Including a buoyancy source term in the turbulence model improved interface sharpness and corrected the over-production of turbulent kinetic energy at a negligible computational cost. For the U-Bend case, choosing a specific geometric reconstruction scheme had minimal effect on the solution’s accuracy. Therefore, interFoam with a turbulence buoyancy term is recommended as a cost-effective and accurate approach.