Abstract
In this study, the level set (LS) and immersed boundary (IB) methods were integrated into a Navier–Stokes equation two-phase flow solver, to investigate wave-structure interactions and induced motions of floating bodies in two dimensions. The movement of an interfacial boundary of two fluids, even with severe free-surface deformation, is tracked by using the level set method, while an immersed object inside a fluid domain is treated by the IB method. Both approaches can be implemented by solving the Navier–Stokes equations for viscous laminar flows with embedded objects in fluids. For accurate treatment of the solid–liquid phase, appropriate source terms as forcing functions to take into account the hydrodynamic effects on the body boundaries are added into the governing equations. The integrated compact interfacial tracking techniques between the interfaces of gas–liquid phase and the solid–liquid phase allow the use of a combined Eulerian Cartesian and Lagrangian grid system. Problems related to the fluid-structure interactions and induced motions of a floating body, such as (a) a dam-break wave over a dry bed; (b) a dam-break wave over either a submerged semicircular or rectangular cylinder; (c) wave decomposition process over a trapezoid breakwater; (d) a free-falling wedge into a water body; and (e) wave packet interacting with a floating body are selected to test the model performance. For all cases, the computed results are found to agree reasonably well with published experimental data and numerical solutions. For the case of modeling wave decomposition process, improved solutions are obtained. The detailed features of flow phenomena described by the physical variables of velocity, pressure and vorticity are presented and discussed. The present two-phase flow model is proved to have the advantage of simulating the cases with induced severe interfacial oscillations and coupled gas (or air) motions where the single-phase model may miss the contributions of the air motions on the interfaces. Additionally, the proposed method with uses of the LS and IB methods is demonstrated to be able to achieve the reliable predictions of complex flow fields.
Highlights
Obtaining solutions of a hydrodynamic model for the studies of complex two-phase flows, such as the propagation of surge fronts, movement of free-surface by a moving body, or waves pass over either completely or partially immersed structures, is an important subject in coastal and ocean engineering applications [1,2]
Using the developed 2D two-phase flow model that integrates the approaches of level set (LS), immersed boundary (IB), and structural responses, selected fluid-structure interaction problems are investigated
The study cases include the following: (a) a uniform flow passing through a circular cylinder to verify the adopted IB methodology, (b) two cylinders moving against each other to test the moving boundary effect, (c) dam-break flows to examine the free-surface tracking capability, (d) dam-break wave flowing over a submerged structure, (e) wave decomposition process over a submerged trapezoid breakwater, (f) a free-falling wedge, and (g) wave packet interacting with a floating body
Summary
Obtaining solutions of a hydrodynamic model for the studies of complex two-phase flows, such as the propagation of surge fronts, movement of free-surface by a moving body, or waves pass over either completely or partially immersed structures, is an important subject in coastal and ocean engineering applications [1,2]. The key issue of modeling free-surface flows is the treatment of moving. The aspect of solving the free-surface flow problem is mainly the description of the mesh movement, using one of the following methods: Eulerian [3,4,5,6], Lagrangian [7,8,9,10], or arbitrary. The significant studies of the Eulerian method are to track the fluid interfaces as the fluid moves through the meshes. The most popular method under this category is the volume of fluid (VOF)
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