Session K.pdf - Clarkson University

57.00056.000Elevation (m)55.00054.00053.000Observed Dataon February 2000Open WaterRating Curve52.00051.0000.0 1000.0 2000.0 3000.0 4000.0 5000.0discharge (m 3 /s)Fig. 3. Limestone tailrace staging during February 2000Plots of tailrace elevation vs. water discharge, as show in Figures 2 and 3, are generatedfrom the recorded data for the months of 1999-2000 winter to show the anchor ice damstaging effect. It can be seen that the staging effect was less than 1 meter in November.It went up to more than 2 meters in February.THE NUMERICAL MODELA two-dimensional finite element numerical model with coupled hydrodynamic andthermal-ice components has been developed to simulate the flow as well as the watertemperature and frazil ice concentration of the river. The hydrodynamic sub-modelsolves the two-dimensional, depth-averaged, unsteady flow equations. The streamlineupwind Petrov Glerkin concept (Brooks and Hughes 1982, Hicks and Steffler 1992, andBerger and Stockstill 1995) is used in the finite element model with an explicit implementation.The model is capable of simulating transitional flows (Liu and Shen 2003).A simple technique is used to treat dry-and-wet bed conditions. A small flow depth andlarge bed resistance is automatically assigned to the dry area, so that the flow velocitiesat the ‘dry’ areas become negligibly small to approximate the dry bed condition. Themain component of the thermodynamic sub-model is to simulate the water temperature.A finite element model with optimum added viscosity is used for both water temperatureand frazil concentration.The model domain extends from the tailrace of the Limestone Generating Station todownstream of the Sundance Rapids. At the upstream boundary, i.e. the generating stationtailrace, the time-dependent water discharges are specified. At the downstreamboundary, water surface elevations are specified according to the rating curve developedin a previous study (Manitoba Hydro 2000). Several soundings were made in differentyears to provide data for channel bathymetry. Some discrepancies were found betweendifferent data sets (Manitoba Hydro 2000). Additional survey is being planned to resolvethese discrepancies before a detailed calibration can be made. The bathymetry andthe model domain used in the present simulation are presented in Figure 4. The blacklines indicate the sounding lines from field surveys.325