Calculation of stone sill overflowing during low discharges | Proracun prelivanja kamenog praga u recnom koritu pri malim vodama
2009
Jovanovic, M., Gradjevinski fakultet, Subotica (Serbia) | Rosic, N., Gradjevinski fakultet, Beograd (Serbia)
This paper is inspired by a stone sill designed in the channel of the Velika Morava river (near Markovacki bridge, Serbia), in order to ensure water supply of the Thermal Power Plant Morava during low flows, and to terminate erosion of the river bed, thus accelerating its stabilization. The impact of extremely high absolute roughness of the sill is particularly strong during low discharges and small water depths, and is manifested by intensive turbulence and air entrainment. Under such flow conditions, the Manning equation for energy loss calculation is not valid. The method by Hartung and Scheuerlein, applied in this case, considers the water-air mixture, and accordingly offers an iterative procedure for estimation of the roughness coefficient value. The Morava river stone sill case study shows that the water surface longitidinal profiles, calculated by the Manning equation, and by the Hartung and Scheuerlein method, differ significantly. Therefore, small-depth flows over very rough surfaces are not be calculated in a routine way, but have to be considered as a separate local phenomena.
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