Author(s): Andri Gunnarsson; Sigurdur M. Gardarsson; Gunnar G. Tomasson; Helgi Johannesson
Keywords: No Keywords
Abstract: The scope of the study conducted is to verify and optimize a low inflow Froude number stilling basin at Hvammur Hydro Electric Project, in southern Iceland, in a physical model. The model is built according to Froude similitude with a scale ratio of 1/40 and represents the approach flow area to the spillway, the spillway, downstream stilling basin and a discharge channel conveying the flow back to the original river channel. The quality of the rock conditions downstream of the stilling basin is expected to be good and therefore the effect of a shorter and less expensive stilling basin is investigated. In total 4 stilling basin lengths were tested at various operating discharges to identify aspects of performance for the basin and downstream channel. Results indicate that a too short basin has limited capability to form a hydraulic jump and produce turbulent kinetic energy for energy dissipation. A longer basin forms a more conventional hydraulic jump and is better able to handle the extreme fluctuations of forces before returning the flow back to the riverbed. Furthermore, with decreasing stilling basin length a fluctuating component is measured at the downstream end of the stilling basin indicating sweep out of the hydraulic jump.