Hydrodynamic simulations of storm-surge waves on coastal structures are essential for coastal areas in predicting wave and flood damages. In a large scale regional model, the coastal structures, such as networks of coastal highways, floodgates and levees, are often complex in shapes. In addition, the width of those structures are smaller in size compared to the grid sizes which in the ranges of 10s to 100s meters. Therefore, in hydrodynamic simulations, it is not possible to use body fitted mesh to conform with the shapes of those networks due to the complicated shapes, and it is very expensive to resolve these small scale structures with very fine grid resolutions. The Immersed Boundary Method (IBM) allows for overcoming these difficulties with an accurate but less expensive way. Since the structures were represented by immersed boundary (IB) points which do not have to be collocated with grid points, complicates shapes structures and the structures smaller than grid resolutions can be realized, and simple Cartesian grids can be utilized without sacrificing accuracy. In a previous study by the authors, an infinite height floodgate/levee structure has been implemented using an IBM which the IB force terms were added in both u and v equations while no IB force term in z (water-elevation) equation. In this study, the height effect was added to the previous developed model. It is worth mentioning that the background flow model is a 2-D depth-averaged shallow water flow model, and the height effect is not implemented by a 3-D mesh. Instead, it is implemented by adding the IB force to the water-elevation equation. The feedback-force type of IBM was used in this study because of its superior performance on this type of simulations compared to the counterpart direct-forcing IBM as shown in the author’s previous publication. In this study, the CaFunwave package was used as the background flow solver, and the IB implementation was written into an separate function incorporated to the package. The equations solved in CaFunwave are the fully nonlinear Boussinesq-type equations, which are capable of modeling of near-shore hydrodynamics. The original model of CaFunwave is FUNWAVE-TVD. In this paper, constant height and non-constant height floodgates/levees were implemented in the simulations. Non-constant height represents broken floodgate/levee situations that parts of the structure are collapsed. The results of one constant-height gate simulation were compared to the results of a simulation that a finite height gate that was constructed directly from the topography data for validation. The floodgate/levee height and shape effects on the flows and waves were revealed from the simulation results.
Verification and validation of a finite volume immersed boundary method for the simulation of static and moving geometries
