Search

This paper presents the results of an experimental investigation into the hydraulic efficiency of a vertically oriented water intake. Under low submergence conditions, the operation of such an intake is affected significantly by the formation of surface vortices, which result in significant flow reduction and the downstream entrainment of air and swirl. The experimental work considered the fact that vortex formation is governed by the geometrical characteristics of the intake, including the diameter, local shape, submergence, surrounding boundary, etc, and the velocity distribution in the approaching flow. Therefore, an experimental study was conducted to investigate the influence that the local shape and the proximity to nearby boundaries have on the hydraulic performance of a vertical water intake. The results of this experimental investigation will hopefully lead to a better understanding of the phenomena governing the flow in such structures and to the elaboration of improved engineering design guidelines.

This paper presents the results of an experimental study of louvers that are used for diversion of fish from water intakes and canals. This investigation was conducted in two phases. Phase I involved the field testing of a louver with curved slats for the guidance of hatchery-reared juvenile rainbow trout (Onchorhyncus mykiss) for louver angles θ of 7.2° and 17.0°. Phase II was a laboratory study with flat slats placed perpendicular to the approaching flow with θ of 10.0° and 15.0°. The velocity in the bypass in terms of the approach velocity increased to 1.7 and 2.5, respectively, for the curved and flat louvers for a bypass width b equal to 5% of the width of the approach channel B. The discharge in the bypass channel Qb in terms of the discharge in the approach channel Q was 0.15 and 0.20 for b/B = 0.10 for the curved and flat louvers, respectively, and Qb/Q = 0.07 for b/B = 0.05 for both the curved and flat louver slats. Key words: fish diversion, louvers, canals, open channels, water intakes, turbulent flows.

Frazil ice is generated in ‘supercooled’ water upstream of an ice cover, and presents an operational hazard to any water intake for hydroelectric and steam power plants and municipal water supplies.The electric heating of trash racks incorporated in water intakes is one of the recognized methods of preventing the deposition of frazil ice on the racks themselves and the ultimate (if allowed to continue unchecked) complete blockage of the intake. In this paper the authors treat the structural and electrical design and the in-service performance of an electrically heated trash-rack system at the Twin Falls Power Development in central Labrador.The power dissipated in the trash-rack heating system for each 50 000 kW machine was approximately 250 kW, i.e., some 0.7% of unit rating.The Twin Falls rack heating installation gave satisfactory performance over some 12 years of winter operation, since its placement in service for the winter of 1962–1963.