Undular Hydraulic Jumps: Critical Analysis of 2D RANS-VOF Simulations

AbstractNumerical simulation of undular hydraulic jumps, which occur at an inflow Froude number slightly above unity, remain an important and enigmatic challenge in hydraulic engineering. In this study, a systematic assessment of the two-dimensional (2D) Reynolds averaged Navier Stokes–volume of fluid (RANS-VOF) equations coupled with the k–ω shear stress transport (SST) turbulence model was carried out for the simulation of undular jumps. The modeling strategies adopted for obtaining a stable undular jump profile are highlighted in this paper. The correlation between turbulence intensity at the jump toe and jump characteristics is also demonstrated. Comparison of laboratory observations with results obtained from experiments conducted under different discharge, approach Froude number, and inflow conditions demonstrated that the proposed 2D RANS model can accurately reproduce the key free-surface characteristics corresponding to undular jumps. The model was capable of reproducing the velocity and pressure fields with greater accuracy than the depth-averaged model. The model was also successful in reproducing the bottom recirculation region below the first wave crest for undular jumps with partially developed boundary layer at the jump toe. The proposed 2D RANS-VOF computational fluid dynamics (CFD) model coupled with the k–ω SST turbulence closure equation is, therefore, recommended as an efficient tool for hydraulic computations, especially for the simulation of weak undular jumps.