Modeling of wave breaking and wave-structure interactions by coupling of Fully Nonlinear Potential Flow and Lattice-Boltzmann models
Date of Original Version
In this work, we report on the development and initial validation of a new hybrid numerical model for strongly nonlinear free surface flows, including wave breaking and wave-structure interactions. Specifically, a two-dimensional numerical wave tank (NWT) based on Fully Nonlinear Potential Flow (FNPF) theory, and a higher-order Boundary Element Method (BEM), is used to simulate fully nonlinear wave generation and far-field propagation over a possibly complex, but generally sloping, bottom bathymetry. A particle-based Lattice Boltzmann (LB) model is coupled with (or nested within) the FNPF-NWT, in the region where breaking would normally occur (e.g., upper part of a slope) and interrupt FNPF simulations. The coupled model is able to capture breaking and post-breaking (or wave-interaction) phenomena that involve more complex physics than represented by FNPF theory. Turbulence, in particular, is represented in the LB model by a Large Eddy Simulation (LES) scheme, based on a Smagorinsky model. In applications, we first validate the model for a one-way weakly coupled scheme, in which the LB model is initialized in the near-field, and then possibly driven on its boundary, by the wave-induced far-field velocity and pressure and their derivatives, computed within the NWT. In the paper, we formulate a fully (or strongly) coupled approach, in which the flow is first decomposed into irrotational and viscous perturbation parts. The latter lead to new terms that, by analogy with Navier-Stokes (NS) equations, are expressed as volume forces, that drive LB simulations of the perturbation fields. Applications of this strong coupling approach will be presented at the conference. © 2010 by The International Society of Offshore and Polar Engineers (ISOPE).
Proceedings of the International Offshore and Polar Engineering Conference
Janssen, Christian F., Stéphan T. Grilli, and Manfred Krafczyk. "Modeling of wave breaking and wave-structure interactions by coupling of Fully Nonlinear Potential Flow and Lattice-Boltzmann models." Proceedings of the International Offshore and Polar Engineering Conference 3, (2010): 686-693. https://digitalcommons.uri.edu/oce_facpubs/154