Laboratory experiments and numerical modeling of infragravity wave refraction and convergence on a reef platform

Infragravity waves, characterized by water surface fluctuations between 25s and 250s, are generated from the release of long waves bound to short-wave group envelopes and temporal variations of breaking locations of these envelopes. On coral reefs, infragravity waves can dominate over short waves and control the processes of sediment transport and stability of reef islands/cay, particularly in combination with high tides and large wave events. A number of studies have investigated the development of infragravity waves in relation to a cross-section of reef shape, but few studies have attempted to address two-dimensional planar reefs, considering spatial and temporal variations in wave energy for sediment deposits on reefs. The study aims to characterize the variability of infragravity waves on a reef platform through a laboratory experiment and numerical modeling. The experiment was conducted in a 50m × 50m wave basin with a 1:200 scale reef platform model. The experiment was to quantify wave refraction, propagation from opposite directions through wave diffraction, and wave convergence on the reef platform under varying high swell energy. A wave-resolving wave model FUNWAVE-TVD, is employed to simulate swell and infragravity waves on the reef and the detailed wave hydrodynamics around the location of sediment deposits. Furthermore, the effects of wind stress on the development of infragravity waves on the reef platform are studied by the model incorporating a wind stress term. We also conduct a sensitivity study of wind drag parameterization to evaluate the effects of wind on the development of infragravity waves. These findings will provide crucial insights into accurate wave dynamics for predicting sedimentary processes and morphodynamics of reef platform islands.