An interpolated bounce-back based lattice Boltzmann method for floating structures interacting with free surface flows

• IBB-based LBM with VOF is developed for simulating floating/partially submerged structures. • It is thoroughly discussed under hydrostatic and dynamic conditions and validated against experiments. • Galilean-invariant momentum exchange method is extended for floating structures. • A set of gas-liquid-solid interface identification rules is proposed to avoid unphysical liquid adhesion. • Dynamic-pressure framework and consistent initial condition are incorporated for reducing force fluctuation. Within the lattice Boltzmann method (LBM), we develop a new numerical model for accurately and robustly simulating the coupled interaction between air-water flows and partially submerged floating rigid bodies. The computational approach integrates the interpolated bounce-back fluid-structure interaction (FSI) method with a volume-of-fluid (VOF) approach for simulating two-phase immiscible fluid flows. We introduce the consistent initial condition iteration as the refilling scheme for new-born fluid nodes and implement a dynamic-pressure framework in the present numerical model, both for mitigating severe force fluctuations caused by the staircase geometric approximation and force imbalance between hydrostatic pressure gradient and gravity. To accurately evaluate hydrodynamic forces acted on floating bodies, which depend on submerged depth, a hydrostatic pressure-related molecular equilibrium distribution function implemented in a sub-grid system is incorporated into the Galilean-invariant momentum exchange method (GIMEM). Moreover, a set of gas-liquid-solid interface identification rules is proposed to suppress spurious currents that cause unphysical liquid adhesion to the solid surface. The developed LBM model is validated through six benchmark cases in both hydrostatic and dynamic scenarios, systematically progressing from fully submerged to partially submerged structures and from stationary to moving configurations: a free-settling immersed circular particle, static buoyant circular cylinder, water exit of a circular cylinder with prescribed velocities, dam-break flow over an obstacle, and water enter of a circular cylinder, and water wave interaction with a free-floating rectangular box. The numerical results compared to available experiments demonstrate the model’s accuracy and robustness in predicting nonlinear free surface deformations and the motion responses of partially submerged structures interacting with air-water flows.