Numerical Simulations of the Fish Passage Facilities at Lower Granite Dam
Abstract : The purpose of these numerical simulations is to investigate possible modifications to the fish diversion facilities currently installed at Lower Granite Dam. These modifications are intended to refine the flow field just upstream of the powerhouse thereby improving the juvenile salmonid attraction potential. A pressure-based finite volume, computational fluid dynamics code was utilized to solve the Reynolds-averaged Navier-Stokes equations. The computational grids, comprising between 350,000 and 1,000,000 nodes, simulated a region encompassing the entire dam geometry as well as 5000 feet upstream. This report describes the numerical model, model boundary conditions, numerical grid and general flow field dynamics obtained from the study as well as providing recommendations for future work pertaining to numerical studies of surface collection facilities.
Abstract The ring-shedding process in the Agulhas Current is studied using the ensemble Kalman filter to assimilate Geosat altimeter data into a two-layer quasigeostrophic ocean model. The properties of the ensemble Kalman filter are further explored with focus on the analysis scheme and the use of gridded data. The Geosat data consist of 10 fields of gridded sea surface height anomalies separated 10 days apart that are added to a climatic mean field. This corresponds to a huge number of data values, and a data reduction scheme must be applied to increase the efficiency of the analysis procedure. Further, it is illustrated how one can resolve the rank problem occurring when a too large dataset or a small ensemble is used.