![Sample our Built Environment journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5926/TOC-Subject-Sample-2021-Built-Environment.jpg"})
ABSTRACT
Intake free-surface vortices can cause efficiency losses, flow fluctuations and even structural damages. Experiments were performed to examine the effect of entrance shapes on the critical submergence. Seven entrance shapes were devised and tested, including a square-edged, a bell-mouthed, three symmetrical conical and two conical profiles with eccentricity. The focus of the study was on a range of Froude numbers from 0.25 to 0.65. The square-edged shape appeared to show the highest local head-loss compared to other shapes. Steady counter-clockwise vortices characterize all the intake profiles except in a narrow water tank. The experiments show both discrepancy and similarity between the intake profiles. The critical submergence of the bell-mouthed intake is lower when compared to the square-edged shape. For the other profiles, it is proportional to the Froude number. A closer sidewall may lead to larger critical submergence in the case of weak circulations. The results demonstrate that the intake-entrance profile has an important effect on the critical submergence.
Acknowledgements
The experimental study is a research project in the field of hydraulic engineering, jointly financed by the Swedish Vattenfall Group and the Swedish Hydropower Centre (Svenskt Vattenkraftcentrum, SVC). The participation of the third author was supported by the STandUP for energy collaboration initiative. The authors wish to thank Cristian Andersson and Sara Sandberg, SVC, for project coordination and Sören Eriksson, Vattenfall R&D, for assisting with improvements to the vortex test rig. The authors also thank professor Willi Hager and two anonymous reviewers for their valuable comments, which significantly improved the quality of the paper.