Bay and Estuary Simulation

Powerful simulation tools are crucial to understand and predict transport and reaction of chemicals in bays and estuaries. Such tools include a hydrodynamics simulator, such as ADCIRC or UTBEST, which simulates the flow of water in the domain of interest, and a chemical transport simulator, such as CE-QUAL-ICM, which simulates the reactions between chemicals in the bay and transport of these chemicals. For a complete simulation system for bays and estuaries, the hydrodynamics simulator needs to be coupled to the chemical transport simulator, since the latter uses the output of the former to simulate the transport of chemicals within the domain. As the chemical reactions have little effect on the circulation patterns, the fluid velocity data can be generated once and used for many contamination studies. However, coupling the two simulators to form a complete system is not a straightforward process for several reasons. First, the chemical transport simulator can be used to simulate changes over a long period of time, from days to tens or hundreds of years. This requires large amounts of hydrodynamics simulation output to be stored to and retrieved from disks and possibly from tertiary storage. Second, the chemical transport simulator may use coarser time steps than the hydrodynamics code. Moreover, the grids used by the chemical simulator may be different from the grids the hydrodynamic simulator employs. Thus, post-processing of large output data set from the hydrodynamics simulator is required to generate the proper input to the chemical transport simulator. One of the post-processing operations is averaging the velocity values over several time steps of the hydrodynamics simulation to generate values for coarser time steps of the chemical transport simulation. The other operation is a projection of the averaged velocity values on the unstructured spatial grid used by the hydrodynamics simulator to flow values on another unstructured grid used by the chemical transport simulator. Optimized storage, retrieval and processing of the output of the hydrodynamics simulator as and when needed by the chemical transport simulator is crucial to efficient coupling of the two simulators.

In this project, we are coupling hydrodynamics simulators with reactive chemical transport simulator using T2, a customizable parallel database for multi-dimensional datasets, that we are developing. The hydrodynamics simulator is used to generate water flow output (e.g., velocities at the grid nodes), which is stored into T2. When the chemical transport simulator requests hydrodynamics data from T2 to compute transport of chemicals, T2 will perform the optimized retrieval and post-processing of the hydrodynamics outputs as required by the chemical transport simulator. For post-processing and projection between different unstructured grids, T2 will use a code under development at the University of Texas, Austin, called UT-PROJ.

Related Information:	Publication List Crisis Management in Bays and Estuaries, NPACI enVision,   Volume 15, Number 1, January - March 1999 Active Data Repository Accelerates Access to Large Data Sets, NPACI enVision,  Volume 14, Number 2, April - June 1998
Presentations:	NPACI Programming Tools and Environments, Pasadena, California, August 1998 Large Irregular Datasets and the Computational Grid, Workshop on Programming Environments, Clusters, and Computational Grids for Scientific Computing, Walland, Tennessee, September 2-4, 1998