Assessment of interface capture schemes in simulating spilling breakers

Wave breaking on coastal slopes drives critical nearshore processes, yet resolving its multiphase dynamics remains challenging due to interface smearing in numerical models and measurement limitations in aerated regions. This study investigates the hydrodynamics of two spilling breaker conditions on a 1:15 slope, with emphasis on propagation behavior, interface evolution, and spectral energy transfer. A comparative analysis of wave morphology between the geometric reconstruction-based IsoAdvector and the algebraic compression-based Multi-dimensional Universal Limiter for Explicit Solution (MULES) methods was conducted using numerical wave flumes, supported by synchronous high-resolution measurements of free surface elevation and flow fields via ultrasonic wave gauges and particle image velocimetry. The breaking process was categorized into four sequential phases: pre-breaking deformation, aerated surface layer formation, bubble-laden interface development, and fragmented free-surface stabilization. Comparative analysis revealed distinct methodological performances: IsoAdvector maintained a sharp interface (2 cells thick) with low mesh sensitivity and achieved a higher refined index of agreement (dr) with experimental surface elevation, accurately capturing crest curvature, jet dynamics, and bubble formation. In contrast, MULES produces a diffuse interface (2 cells thick) with mesh-dependent phase shift; however, it offered approximately 4.7 % higher computational efficiency in fine-mesh simulations. Accordingly, IsoAdvector is recommended for high-fidelity interface-resolved studies, while MULES is suitable for large-scale applications prioritizing computational economy. Spectral analysis further showed that increased wave height intensifies nonlinear interactions, resulting in earlier breaking, broader energy distribution, and enhanced dissipation. These findings provide key insight into nearshore wave transformation and guidance for selecting numerical approaches in breaking wave simulations.