Author(s): N. Solheim; E. Pummer; L. Lia
Linked Author(s): Leif Lia, Elena Pummer, Nils Solheim
Keywords: Spillway capacity; Approach channel; Oblique; Contractions; Losses
Abstract: Spillway design guidelines include a theoretical capacity that incorporates the discharge coefficient, which considers various real-world factors that deviate from ideal conditions, such as vertical contractions. Additionally, approach flow is assumed to be normal to the spillway axis. However, due to spatial constraints of the hydraulic structure’s footprint, or as seen during high return-period flood events, the flow in natural waterways may approach the spillway at an oblique angle, deviating from the assumed perpendicular approach. This study presents experimental results from a spillway model incorporating an obstruction over one-third of the channel width, representing a large pier or gate house. This induces a contraction over the spillway crest, which diminishes the spillway capacity significantly. From the base case, the approach channel angle is adjusted obliquely to the spillway axis in increments from 0° to 15º from the streamwise direction. Discharge capacity if shown to decrease with increasing angle of lateral approach and with increasing discharge. The maximum decrease is found to be close to 2 %. The experimental results are compared to previous studies of similar phenomena. Furthermore, velocity measurements from the various model configurations are presented, illustrating the alterations in the flow field upstream of the weir.
Year: 2024