model was used to drive Che system only for storm events. 



?1. The two embedded grids utilized in this study (nearshore and shore 

 process) contain successively finer resolution with resultant greater detail. 

 Therefore stability requirements as governed by Equation 18 necessitate the 

 use of successively smaller time-steps in simulations with these models. Data 

 are transferred between coupled grids at the outer boundary cells of Che 

 embedded grid. Coupling grids are designed such that Che cell size '.x and 

 Che derivacive -r— (in the direction orthogonal to the coupling boundary) are 



do. 



equivalent in the coupling cells of both the driving and driven grids. In the 

 direction normal to the coupling boundary, cell expansion and contraction are 

 allowed to proceed independently, thus requiring spatial interpolation of the 

 transferred data. A temporal interpolation is also required due to the small 

 time-step needed by the embedded grid. Care must be taken to ensure that 

 coupling grids contain similar water volumes within the embedded griu cover- 

 age, particularly at the coupling boundaries in order to preserve hydrodynamics 

 between the grids. 



22. The data transferred between models consist of n , u , and v at 

 each coupling cell. A utility program performs the necessary spatial and 

 temporal interpolations between coupling grids. It should be noted that 

 connections are r:oc CoCally dynamic in Che sense that the simulations are 

 independent and not concurrent. Communication is unidirectional from the 

 driving to the driven model. 



18 



