Model investigations of the outlet works for the Clinton and Fort Scott Dams were concerned with the development of satisfactory stilling basins for a wide range of discharges and tailwater conditions. Of particular interest were low-flow conditions in which the invert of the outlet is submerged by tailwater or in which there is little drop from the outlet portal invert to tailwater. Although the structures were similar in design and purpose, geometric differences, particularly the reduction in drop from the outlet invert to the stilling basin for Fort Scott, required the use of separate model studies. Both studies were conducted with a 1:16-scale model that reproduced a portion of the outlet conduit, the stilling basin, and about 800 ft of the exit channel. In the case of the Fort Scott study, the stilling basin was connected to the Clinton conduit. Pressures measured throughout the conduit were positive for all discharges, with little or no fluctuations, and the hydraulic gradient at the conduit outlet for full conduit flows reached, as expected, about 0.60 of the conduit height. Performances of the original design basins for both projects were unacceptable, as unstable hydraulic action and eddy formation occurred in the basins at or near expected tailwaters with flows less than 1600 cfs. In the case of the Clinton Dam study, decreasing the flare of the outlet transition sidewalls and reducing the elevation of the basin floor (type 15 basin) resulted in adequate, if not ideal, performance. Adequate performance of the Fort Scott basin required a decrease in basin width and a reduction in apron elevation (type 7 basin). This basin barely maintained a jump with the design discharge (7370 cfs). The top elevations of the original basin walls for both projects were sufficient to prevent overtopping. A riprap plan of protection was developed for the exit channels. Investigation of the 1:5-scale model of the low-flow outlet for the Fort Scott outlet works revealed that the most satisfactory location of the control gate was within and perpendicular to the conduit. With the control gate located at the conduit entrance, the high-velocity jet under the gate was unstable, tending to seal off the conduit at all openings greater than 1 ft.
Outlet Works Stilling Basins, Clinton and Fort Scott Dams, Wakarusa and Marmaton Rivers, Kansas: Hydraulic Model Investigation
Technical Report ; H-73-6
1973
6790902
Report
Elektronische Ressource
Englisch
HENRY – Bundesanstalt für Wasserbau (BAW) | 1973
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