A.Jacob Odgaard, Ph.D., P.E., F.ASCE; Troy C. Lyons, P.E., M.ASCE; and Andrew J. Craig are the recipients of the Karl Emil Hilgard Hydraulic Prize for their paper “Baffle-Drop Structure Design Relationships,” published in the September 2013 issue of ASCE’s Journal of Hydraulic Engineering.
The Karl Emil Hilgard Hydraulic Prize is presented to the author or authors of the paper that is judged to be of superior merit in dealing with a problem of flowing water, either in theory or in practice.
In this article, the authors describe a baffle-drop structure as a flow conveyance structure that can be used for transport of urban storm-water down to underground storage tunnels where the water cascades down the structure from baffle to baffle and plunges into a pool at the bottom from where it is conveyed to the tunnel through an adit.
The structure has been used successfully in a limited number of urban drainage schemes. However, its hydraulics and air entrainment characteristics are not fully understood. Therefore, using a series of laboratory experiments, an analysis has been tested and validated that may be used for design. The analysis provides a dimensionless relationship between key variables, including design discharge, shaft diameter, baffle spacing, and position of a vertical wall dividing the shaft in a dry and a wet portion. Using this relationship the shaft can be designed to maintain atmospheric pressure throughout its height with little or no air being entrained into the tunnel.