A combined volume of fluid and immersed boundary method for free surface simulations induced by solitary waves

2022 ◽  
Vol 245 ◽  
pp. 110560
Author(s):  
Qiu Jin ◽  
Dominic Hudson ◽  
Pandeli Temarel
Keyword(s):  
Free Surface ◽  
Solitary Waves ◽  
Immersed Boundary Method ◽  
Volume Of Fluid ◽  
Immersed Boundary ◽  
Boundary Method

A Combined Volume of Fluid and Immersed Boundary Method for Modelling of Two-Phase Flows with High Density Ratio

2021 ◽  
Author(s):  
Qiu Jin ◽  
Dominic Hudson ◽  
W.G. Price
Keyword(s):  
Boundary Layer ◽  
Immersed Boundary Method ◽  
Density Ratio ◽  
Volume Of Fluid ◽  
High Density ◽  
Immersed Boundary ◽  
Two Phase Flows ◽  
Two Phase ◽  
Boundary Method ◽  
High Density Ratio

Abstract A combined volume of fluid and immersed boundary method is developed to simulate two-phase flows with high density ratio. The problems of discontinuity of density and momentum flux are known to be challenging in simulations. In order to overcome the numerical instabilities, an extra velocity field is designed to extend velocity of the heavier phase into the lighter phase and to enforce a new boundary condition near the interface, which is similar to non-slip boundary conditions in Fluid-Structure Interaction (FSI) problems. The interface is captured using a Volume of Fluid (VOF) method, and a new boundary layer is built on the lighter phase side by an immersed boundary method. The designed boundary layer helps to reduce the spurious velocity caused by the imbalance of dynamic pressure gradient and density gradient and to prevent tearing of the interface due to the tangential velocity across the interface. The influence of time step, density ratio, and spatial resolution is studied in detail for two set of cases, steady stratified flow and convection of a high-density droplet, where direct comparison is possible to potential flow analysis (i.e. infinite Reynold's number). An initial study for a droplet splashing on a thin liquid film demonstrates applicability of the new solver to real-life applications. Detailed comparisons should be performed in the future for finite Reynold's number cases to fully demonstrate the improvements in accuracy and stability of high-density ratio two-phase flow simulations offered by the new method.

scholarly journals A Discrete-Forcing Immersed Boundary Method for Moving Bodies in Air–Water Two-Phase Flows

2020 ◽  
Vol 8 (10) ◽  
pp. 809
Author(s):  
Haixuan Ye ◽  
Yang Chen ◽  
Kevin Maki
Keyword(s):  
Free Surface ◽  
Immersed Boundary Method ◽  
Surface Profile ◽  
Field Extension ◽  
Immersed Boundary ◽  
Two Phase Flows ◽  
Two Phase ◽  
Practical Applications ◽  
Boundary Method ◽  
Immersed Boundaries

For numerical simulations of ship and offshore hydrodynamic problems, it is challenging to model the interaction between the free surface and moving complex geometries. This paper proposes a discrete-forcing immersed boundary method (IBM) to efficiently simulate moving solid boundaries in incompressible air–water two-phase flows. In the present work, the air–water two-phase flows are modeled using the Volume-of-Fluid (VoF) method. The present IBM is suitable for unstructured meshes. It can be used combined with body-fitted wall boundaries to model the relative motions between solid walls, which makes it flexible to use in practical applications. A field extension method is used to model the interaction between the air–water interface and the immersed boundaries. The accuracy of the method is demonstrated through validation cases, including the three-dimensional dam-break problem with an obstacle, the water exit of a circular cylinder, and a ship model advancing with a rotating semi-balanced rudder. The flow field, free-surface profile and force on the immersed boundaries (IBs) are in good agreement with experimental data and other numerical results.

scholarly journals An immersed boundary method with iterative symmetric interpolation for irregular surface topography in seismic wavefield modelling

2020 ◽  
Author(s):  
Xiang Li ◽  
Gang Yao ◽  
Fenglin Niu ◽  
Di Wu
Keyword(s):  
Free Surface ◽  
Finite Difference ◽  
Surface Topography ◽  
Immersed Boundary Method ◽  
Acoustic Waves ◽  
Interpolation Method ◽  
Immersed Boundary ◽  
Boundary Method ◽  
Wavefield Simulation ◽  
Irregular Free Surface

Abstract The irregular free surface topography has a significant impact on simulations of seismic wave propagation. Therefore, an accurate representation of the irregular free surface is required for an accurate wavefield simulation. We propose an immersed boundary method used in fluid dynamics calculation to simulate acoustic waves with finite-difference in media with irregular surfaces. First, we set the number of ghost layers to half the length of the finite-difference stencil. Then, we define mirror points by orthogonally projecting the ghost points to fractional points below the free surface. We calculate the wavefield at these mirror points using an iterative symmetric interpolation method. Finally, we set the wavefield at the ghost points to the negative value of the wavefield of their corresponding mirror points. The proposed iterative symmetric interpolation method allows computing the wavefield at the mirror points more accurately and stably than the conventional immersed boundary methods. Numerical examples validate the accuracy and stability of this method in seismic forward modelling with strongly varying topography.

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