Turbulence closure modeling of wave-driven free-surface flows

This study investigates turbulence modeling in free-surface flows, with a focus on wave-driven turbulence and wave–structure interactions (WSI). The work examines the interplay between high-shear turbulence during breaking waves and low-turbulence regions under non-breaking waves. Using direct numerical simulation (DNS) data and Reynolds-averaged Navier–Stokes (RANS) calculations, the study explores the closure physics of different length scale model formulations and constitutive relations, with respect to the accurate computation of wave amplitude and various turbulence features. Constitutive relations that uphold realizability constraints are shown to be critical for preserving wave amplitude, especially in high-shear environments. This is due to the fact that, in such regions, turbulence behaves more like an elastic medium rather than a viscous one. It is also demonstrated that the length scale model must exhibit reasonable behavior across both high-shear and low-turbulence regions. Model combinations that employ low-turbulence corrections in conjunction with realizable constitutive relations are most effective in capturing wave dynamics and maintaining wave energy in non-breaking regions. These findings inform the development of robust, physically consistent turbulence models for simulating complex environmental and marine free-surface flows.