Coastal ocean hydrodynamic models are used to simulate water surface elevations and circulation in oceans, lakes, estuaries, rivers and floodplains. One such model is ADCIRC (ADvanced CIRCulation), which was originally developed more than 15 years ago and which is used for a variety of purposes, including naval fleet operations, storm surge predictions, and larvae transport. ADCIRC assumed fixed land boundaries until a wetting and drying algorithm was implemented in 1995. However, this algorithm had two components that limited the performance of the model. First, nodes were required to remain “wet” or “dry” for a user-specified number of time steps before changing states. This component became restrictive in relatively flat regions, such as a flood plain, where it caused oscillations and slowed the propagation of flood waves. Second, in regions with steep bathymetry, mass balance problems and instabilities would occur when a thin film of water was allowed to flow uninterrupted. Changes based on a more physically-accurate description of the wetting and drying process were made recently to address these two problems. This paper describes the wetting and drying algorithm and those changes, and it applies the improved algorithm to an idealized domain that was designed specifically to test the two problem areas. The improved algorithm provides better stability and mass balance properties.
It makes me wonder why we’re wasting our time with math and equations and computers and what-not.
Hydrodynamic models are used for a variety of purposes, such as the modeling of hurricane storm surges, the study of tidal circulation patterns, and the planning of naval fleet operations. One such hydrodynamic model is ADCIRC (ADvanced CIRCulation), which was developed more than 20 years ago and has been refined continuously by researchers across North America. ADCIRC is based on the shallow water equations and includes many of the features necessary to model complex hydrodynamic systems. However, some of these features were implemented in an attempt to solve specific problems, and their behaviors were never rigorously assessed. For instance, the model uses a wetting and drying algorithm to simulate the ebb and flow of tides in coastal regions. This behavior is important in many applications, and it must be modeled correctly. This research thesis will: (1) refute an attack on the usefulness of the finite volume method for computing mass balance errors, (2) lay the groundwork for a future study that will automate the placement of grid points based on a minimization of local mass balance error, (3) implement and assess the wetting and drying algorithm in one-, two-, and three-dimensional versions of the ADCIRC model, (4) identify a set of optimal parameters for wetting and drying simulations, (5) prove that recent updates to the wetting and drying algorithm were beneficial, and (6) show that smaller mass balance errors are obtained when they are computed for each vertical element in the water column.
