2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/107794Nonlinear coupling between eigenmodes of a system leads to spectral energy redistribution. For multi-wavespeed chaotic billiards the average coupling strength can exhibit sharp discontinuities as a function of frequency related to wavevector coincidences between constituent waves of different wavespeeds. The phenomenon is investigated numerically for an ensemble of 2D square two-wavespeed billiards with rough boundaries and quadratic nonlinearity representative of elastodynamic waves. Results of direct numerical simulations are compared with theoretical predictions.Chaotic Dynamicstext