Energy and Momentum Velocity Coefficients for Calibrating Submerged Sluice Gates in Irrigation Canals

There is renewed interest in developing calibration methods for gates operating in submerged conditions in irrigation canals. In the present study, a new method based on a generalization of the standard energy-momentum method that accounts for variations in the energy and momentum velocity coefficients is proposed, for the following reasons. First, it was found that the assumption of uniform submerged jet velocity to account for the kinetic energy head and momentum flux is in reality equivalent to assuming a parabolic relationship between the Coriolis and Boussinesq coefficients. Second, literature investigations showed that the coefficients for the downstream side of submerged gates are notably greater than unity, and the implicit parabolic relationship between these coefficients in the standard energy-momentum method is inadequate, at least for high submergence conditions. The proposed energy-momentum method was evaluated using the data obtained from four gates operating in an irrigation canal in Southern Spain. Improvements in accuracy compared to the standard energy-momentum method (with a constant contraction coefficient $C_c=0.61$ ) were obtained. The results indicate that the calibration of coefficient approach provides a means to improve the energy-momentum method by (indirectly) accounting more accurately for nonuniform velocity effects in the energy-momentum equations.