Effect of Current Reynolds Number on the Flow Structure of Waves Following Current for Varying Wave Frequencies

Abstract The current work uses computational simulations to study the effect of the Reynolds number on phase-averaged velocity profiles and turbulence characteristics for environments with wave–current flow. The presented computational model utilized a Reynolds-averaged Navier–Stokes (RANS) solver, which is closed using K–ω shear stress transport (SST) equations. The volume of fluid (VOF) method is employed to capture and analyze the wave profiles and the related water surface dynamics. A new user-defined function is created to simulate the waves, which are then imposed on a steady current introduced at the inlet. The model is validated against established experimental data, which shows strong agreement. The research examines the impact of varying wave frequencies on changing background channel flow Reynolds number on the phase-averaged flow characteristics. Inferences regarding the near-surface and near-bed turbulence characteristics are drawn from the background current interaction with the surface wave. Streamwise velocity profiles agree with the existing literature on wave current interaction for lower-frequency waves, but when the frequency is increased, the results deviate. The turbulence kinetic energy resulting from combined wave–current motion is found to be more for waves superposed on a background current with a low velocity than waves superposed on high-velocity background flow. It was also found that the analytical model put forward by Grant–Madsen needs adjustment to be applicable to waves across all frequency ranges. The streamwise velocity profiles also deviate from the established literature for waves with higher frequencies.