Hydraulic and flow measurement performance of integrated sluice gates in U-shaped channels with varying slopes

Integrated measurement and control sluices (IMCS) are systematically investigated in U-shaped channels through both experimental and numerical methods to examine the effects of channel bottom slopes on measurement accuracy and flow capacity. The sluice gate opening degree considered is e = 4–18 cm, corresponding to incoming flow rate Q = 10–50 L/s. The support system at the bottom of the channel allows for flexible adjustment of the slope, with a setting range of 1/5000-1/100. The water surface profile, Froude number, flow velocity distribution, critical state of sluice gate flow and weir flow, calculation equations, and flow measurement accuracy are analyzed. Results show that, under varying operating conditions, the upstream water depth increases directly with the flow rate, while decreasing as the gate opening and bottom slope increase. Conversely, the downstream water surface profile exhibits an inverse trend in response to changes in flow rate and gate opening. Notably, the length of the hydraulic jump significantly increases with steeper bottom slopes. The derived measurement formula for free outflow demonstrates a high correlation coefficient and accuracy, with the relative error consistently remaining below 5 %, thus meeting the required accuracy standards for water measurement in irrigation channels. Furthermore, the proposed IMCS system is capable of adapting to changes in bottom slope, effectively combining measurement and control functions, avoiding excessive water usage, and enhancing irrigation efficiency. These findings provide valuable insights for the development and application of water measurement infrastructure in irrigation systems.