CRESTS3D
CRESTS3D is a three-dimensional (3D) Coastal, River, and Estuarine Simulation Tool System. The model solves the 3D shallow water flow equations to simulate the currents induced by river runoff, tides, winds and waves in coastal, river and estuarine waters. The eddy viscosity is determined with a modified mixing length model. The model adopts an implicit finite-volume method on a multiple-level quadtree rectangular mesh on the horizontal plane and the sigma coordinate in the vertical direction. The quadtree technique can locally refine the mesh around structures or in high-gradient regions by splitting a coarse cell into four child cells. All the primary variables are arranged in a non-staggered system and stored at cell centers. Fluxes at cell faces are determined with the Rhie and Chow’s momentum interpolation, to avoid potential spurious checkerboard oscillations. Each of the discretized governing equations is solved iteratively using the flexible GMRES method with ILUT preconditioning, and the SIMPLEC algorithm with under-relaxation is used to couple water level and velocity among these equations (Wu and Lin 2011; Wu 2014).
The CRESTS3D flow model is coupled with the spectral wave transformation model, CMS-Wave, which is used to simulate variations of wave-action density in time, space, wave direction and frequency. CMS-Wave solves the wave-action balance equation using a forward marching finite difference method (Mase et al. 2005; Lin et al. 2008). The considered physical processes include wave shoaling, refraction, diffraction, reflection, wave-current interaction, wave breaking, wind wave generation, white capping of waves, vegetation drag, and the influence of coastal structures. In addition, the wave surface roller is simulated by solving the steady-state energy balance equation. The vertical profile of wave radiation stresses is determined by using the method of Mellor (2008).
CRESTS3D is able to simulate the flow in coastal vegetated waters with short waves. The model considers the effects of vegetation on current and waves by including the drag and inertia forces of vegetation in the momentum equations and the wave energy loss due to vegetation resistance in the wave action balance equation (Wu 2014).
The CRESTS3D sediment model simulates multiple-sized sediment transport and the resulting bed change using the non-equilibrium total-load transport model. The bed-load transport capacity and near-bed suspended-load equilibrium concentration under combined currents and waves are calculated using the formulas developed by Wu and Lin (2014). A correction factor is used to account for the hiding and exposure effects of nonuniform sediment transport. The bed is divided into discrete vertical layers and the fractional composition of each layer is tracked in time.
CRESTS3D is coded with CMS2D, which takes advantage of the Surface-water Modeling System (SMS) interface versions 8.2 through 11.1 for grid generation, model setup, plotting and post-processing of modeling results (http://cirp.usace.army.mil/products/cms.php). If the user prepares the CMS2D simulation files through SMS, she/he then can run CRESTS3D by adding only two small files specifying the σ-coordinate layers and so on.
References:
W. Wu and Q. Lin (2011). “An implicit 3-D finite-volume coastal hydrodynamic model.” Proc., 7th Int. Symposium on River, Coastal and Estuarine Morphodynamics, September 6-8, Beijing, China.
W. Wu (2014). “A 3-D phase-averaged model for shallow water flow with waves in vegetated water.” Ocean Dynamics, 64(7), 1061-1071.
W. Wu and Q. Lin (2014). “Nonuniform sediment transport under non-breaking waves and currents.” Coastal Engineering, 90, 1–14, http://dx.doi.org/10.1016/j.coastaleng.2014.04.006 0378-3839.
L. Lin, Z. Demirbilek, H. Mase, J. Zheng, and F. Yamada (2008). “CMS-Wave: A nearshore spectral wave processes model for coastal inlets and navigation projects.” Technical Report ERDC/CHL TR-08-13, Coastal and Hydraulics Laboratory, ERDC, US Army Corps of Engineers, Vicksburg, MS, USA.
H. Mase, K. Oki, T.S. Hedges, and H.J. Li (2005). “Extended energy-balance-equation wave model for multidirectional random wave transformation.” Ocean Eng., 32(8-9): 961-985.
G.L. Mellor (2008). “The depth‐dependent current and wave interaction equations: a revision.” J Phys Oceanogr 38:2587-2596. doi:10.1175/2008JPO3971.1.