Unified analytical solution for group-induced infragravity waves based on Green's function

Short-wave group forcing is a major driving mechanism of infragravity waves. The subharmonic response to wave approaches resonance in shallow water where the velocity equal shallow-water wave-propagating speed. Currently, there lack understanding connection between free and bound components group-induced waves consistency among existing solutions for off- near-resonance conditions intermediate water. Here, unified solution subharmonics derived based on Green's function first time. new valid any intensity able describe behaviour at all depths consistently from angle. proposed reduces depth (Longuet-Higgins & Stewart, J. Fluid Mech. , vol. 13, 1962, pp. 481–504; Zou, Phys. Oceanogr. 41, 2011, 1842–1859), and/or over plane sloping beach (Van Leeuwen, PhD thesis, TU Delft, 1992; Schäffer, 247, 1993, 551–588; Janssen et al. Geophys. Res. 108, 2003, p. 3252; Contardo 51, 2021, 1465–1487; Liao 2749–2765). Unlike previous solutions, function-based describes as continuously radiated away each point source field determined by radiation stress gradients. superposition these yields so-called studies due group-modulated emission through group. Therefore, this provides theoretical evidence that observation dependent surrounding topography. Under full-resonance water, downwave-propagating excited locations interfere with other constructively; therefore, their superposed amplitude proportional travel distance groups. Combined conventional moving-breakpoint model, predicted surf zone present good agreement laboratory observations.