Wave group evolution, wave deformation, and breaking: simulations using LONGTANK, a numerical wave tank

Non-linear, planar wave trains have been simulated numerically using an efficient computational method. This method utilizes matrix diagonalization, based on multi-subdomains. The waves are created by a wavemaker at one end and followed to downtank distances, x/λ of O(102). High resolution of wave shapes has been obtained. This numerical tank, LONGTANK, has been used to study non-linear sideband growth, strong group evolution, wave deformation, energy redistribution in the deformed waves, and jet formation (breaking). Comparisons of steepness at breaking and distance to breaking, as they depend on wave steepness, have been made, with excellent agreement. Similar agreement is shown between simulated and photographed wave shapes in the final stages of breaking. A criterion for the onset of breaking is suggested by the simulations.