Rigorous Asymptotic Models of Water Waves

TL;DR

This paper rigorously derives and analyzes asymptotic models for water waves that incorporate full nonlinearity up to quadratic and cubic interactions, providing theoretical proofs and numerical validation for their accuracy and well-posedness.

Contribution

The paper introduces two new asymptotic water wave models, the quadratic and cubic h-models, with proven well-posedness and error bounds, and develops a numerical algorithm demonstrating their accuracy.

Findings

Models accurately predict water wave behavior even at large steepness.

Error bounds established for the asymptotic models against full water wave solutions.

Numerical simulations confirm the models' effectiveness and show phenomena like corner formation.

Abstract

We develop a rigorous asymptotic derivation for two mathematical models of water waves that capture the full nonlinearity of the Euler equations up to quadratic and cubic interactions, respectively. Specifically, letting epsilon denote an asymptotic parameter denoting the steepness of the water wave, we use a Stokes expansion in epsilon to derive a set of linear recursion relations for the tangential component of velocity, the stream function, and the water wave parameterization. The solution of the water waves system is obtained as an infinite sum of solutions to linear problems at each epsilon^k level, and truncation of this series leads to our two asymptotic models, that we call the quadratic and cubic h-models. Using the growth rate of the Catalan numbers (from number theory), we prove well-posedness of the h-models in spaces of analytic functions, and prove error bounds for solutions of the h-models compared against solutions of the water waves system. We also show that the Craig-Sulem models of water waves can be obtained from our asymptotic procedure and that their WW2 model is well-posed in our functional framework. We then develop a novel numerical algorithm to solve the quadratic and cubic h-models as well as the full water waves system. For three very different examples, we show that the agreement between the model equations and the water waves solution is excellent, even when the wave steepness is quite large. We also present a numerical example of corner formation for water waves.