Prediction of the behavior of hydraulic jumps in canoe chutes

A canoe chute is a series of rapids and pools creating a gradual descent from the elevation of the upstream pool of the dam to the elevation of the pool at the toe of the dam. Each rapid forces a surface jet that causes a hydraulic jump when it enters the slower water of a pool. Most engineering designs have considered the hydraulic jumps formed in canoe chutes to be approximately the same as the hydraulic jumps formed at abrupt drops in the channel bottom. The jumps commonly observed at abrupt drops are A-Jumps formed at high tailwater conditions, waves formed at intermediate tailwater conditions, and B-Jumps formed at low tailwater conditions. Sets of equations have been developed by different authors to describe the A- and B-Jump types that occur at abrupt drops. In a canoe chute, however, there is also a simultaneous horizontal expansion in the channel in addition to an abrupt drop in the channel bottom. Thus, the momentum equations that describe two-dimensional flows at abrupt drops need to be modified to account for the three-dimensional flow caused by the additional horizontal expansion. A 1:7 scale Froude model of one rapid of the canoe chute was constructed in the Ven Te Chow Hydrosystems Laboratory at the University of Illinois. Depth and flow data collected from the physical model were compared against both the original and the modified momentum equations. An empirical method for predicting hydraulic jump behavior was developed. The empirical method is advantageous in that it involves either known or easily measured flow conditions. Copyright ASCE 2004.