This project is the framework of a CFD model for free surface flow coupled immersed boundary method.
The main framework of the numerical model is based on the unstructured mesh Finite Volume Method (FVM) and the second order Total Variation Diminishing (TVD) scheme for discretized equations, which is mainly used to simulate physical problems involving free surface flow, such as the, rivers, lakes and ocean currents. To characterize the hydrodynamics of the natural water system and the environment, the numerical model implements a terrain following σ coordinate system to simulate the free surface.
The Immersed Boundary Method (IBM) provides an excellent approach to the challenges of fluid-structure coupled problems in three-dimensional flows with free surfaces. This project focuses on the numerical simulation of flow and wave structure interactions. More details are available here: An immersed boundary method coupled non-hydrostatic model for free surface flow.
Before starting the numerical model, it is necessary to import the geometric information and boundary conditions of the mesh system. The following section gives a brief introduction to these files.
FSIBM_SET: Numerical model settings file.
MESH(GRD): Mesh file, including vertical section information, mesh node positions and node numbers.
MESH(CUV): Mesh file, including topology relationships of mesh cells, edges and local coordinate information.
BC_FLOW: Boundary condition file for inlet flow.
BC_ELF: Boundary condition file for water elevation.
IBM_Model: Model file for geometric information of virtual boundary.
The numerical model consists of a series of modules, and we present a brief overview of the basic computational modules that operate within a complete time step. The following section provides some details of these basic modules.
- Numerical Settings
SETNUM: Numerical mode setting and mesh file import.
SETBC: Boundary condition setting.
SETIBM: IBM mode setting and boundary model import.
- Numerical Scheme: Free Surface Flow
CONVDIFU / V / W: Discretization and solution of convection and diffusion equations.
TVDSCHEMEH / TVDSCHEMEV: TVD schemes for the flux of the convection and diffusion terms.
PROFELF: Water elevation solver by continuity equation.
PROFV / PROFW: Flow velocity solver by momentum equation.
PROFQW: Sigma velocity solver.
PROFPN: Hydrodynamic pressure solver by continuity equation.
SOLVERBICG: BI-CGSTAB method for solving linear equations.
REUV / UVFN: Update flow field variables.
- Numerical Scheme: Immersed Boundary Method
IBM: Main module of immersed boundary method.
IBMALAUX: Moller Trumbore algorithm, still water depth setting and matrix operation.
IBMALIBC: Ray tracing method for boundary detection.
IBMALIBF: Virtual force term for sharp interface immersed boundary method.
IBMALRGD: Rigid body dynamics module for moving boundary.
IBMCLBD / IBMCLBP: Collision detection module.
- Numerical Results
SAVEDIV: Save data when divergence occurs.
SAVENUM: Save data for post-processing.
The above provides an overview of the basic computational modules within a complete time step. The current model is still under development and we are committed to extending its application and improving its numerical accuracy.