Author(s): Yeo H. Lim; Jacob O. Wieland; Nicholas Kalenze
Linked Author(s):
Keywords: No Keywords
Abstract: The design of stilling basins for pipe outlets to dissipate energy effectively, especially in special constraint conditions, poses a significant challenge. A review of the various aspects of design options shows that, within a limited range of Froude numbers, the location and shape of energy dissipators, splitter block geometry, and drop characteristics are critical in achieving the design goal. When serious faults are found in an existing stilling basin for a 2.44-m (8-ft) pipe outlet of a water supply dam in North Dakota, an experimental study to investigate the replacement options was carried out. This is necessary because literature does not provide clearer guidance on optimizing the use of the limited original space. The new stilling basin has to be reconstructed at the same constrained space because an existing twin-box culvert beneath a 18.3-m high railway embankment is located immediately downstream of the existing basin. A conceptual stilling basin featuring lateral enlargements, a drop, and a sill within a short length was tested using a scaled laboratory model. The basin, with two options of chute and buffer block sets (5-cm and 7.6-cm), was tested under simulated floods of 25,50, and 100-year return periods. The hydraulic model setup, the model construction details, the measurement techniques, and the complex hydraulic jump observed are reported. The observed velocities, jump heights, and energy dissipations of the design options are compared and rationalized. The option with the 7.6-cm blocks has developed hydraulic jumps well within the basin and hence can be used instead of the more elaborate impact-type stilling basins.
Year: 2009