Abstract: The aim of this paper is to make an improvement on hydraulic jump equation in abruptly expanding channel and compare it with the experimental results of predecessors. Under the assumption that average water depth in the backflow region is taken as representative water depth, the general equation of hydraulic jump in abruptly expanding channel is derived according to the principle of momentum conservation. On the basis of improving the concrete expression of the average water depth in the backflow region, a new equation for hydraulic jump in abruptly expanding channel is obtained, and a method for determining the parameters in the equation is given. The conjugate depth ratios obtained by existing equations and the present improved equation are compared with the experimental results. The comparison demonstrates that the average error and the maximum error between the conjugate depth ratio obtained by the present improved equation and the experimental results are the smallest and the accuracy is the highest in the presence of varying expansion ratio of channel. In addition, the present equation is convenient for calculation with explicit solution. Therefore, we recommend the improved equation for hydraulic design of conjugate water depth of hydraulic jump in abruptly expanding channel.

Key words: hydraulic jump in abruptly expanding channel, principle of momentum conservation, hydraulic jump equation, water depth in backflow zone, conjugate depth