Hydraulic performance of the flow measuring flume of imitating long-eared owl wing based on SSA-BP algorithm

Water demand of irrigation areas is required for the flow-measuring flume with simple structure and excellent hydraulic performance. Among them, the morphological structure of long-eared owl wings has been proved as the outstanding noise reduction and excellent drag reduction. The impeded state of the flume in the channel flow field is also similar to the air resistance of the long-eared owl during flight. In this study, the flow-measuring facility was proposed to imitate the shape of long-eared owl. The structure of bird wing was used to design a bionic structure flume. Numerical simulations were combined with the experiments to explore the correlation among various factors. The optimal line shape was determined using internal logical connections. Firstly, Sparrow Search -based BP Neural Network (SSA-BP) was utilized to optimize the spanwise location of the owl wing. The optimal flume shape was achieved with the minimal head loss. The suitability of the optimized flume was also investigated in the irrigation channels. Furthermore, a series of flow measurement tests and numerical simulations were conducted to verify the effectiveness of the optimization. The hydraulic trials were carried out in the Laboratory of Hydraulic Engineering and Hydraulics of Northwest A＆F University in 2024. The channel was set as a flat-slope rectangular channel with the channel length L=10 m, inner width B=0.7 m, and height H=0.4 m. The flow measuring flume was 4.3 m away from the inlet of the channel. The flow measurement experiments were selected as the eight kinds of flow conditions (0.50, 0.54, 0.58, 0.60, 0.62 and 0.66), and six sets of contraction ratios (20-55 L/s, each increase of 5 L/s was a flow gradient). FLOW-3D numerical simulation was combined to analyze the hydraulic parameters, such as the head loss percentage, Froude number, backwater height, and critical submergence degree of the flow measuring flume of imitating long-eared owl wing. The experiments demonstrated that the flow measuring flume exhibited the excellent flow measurement performance after SSA-BP optimization. Within the recommended contraction ratio range of 0.60 to 0.66, the head loss percentage was ranged from 7.75% to 14.21%, the critical submergence degree was from 0.81 to 0.90, the upstream backwater height was from 0.84 to 3.16 cm, and the upstream Froude number was all less than 0.42, fully meeting the precision requirements of irrigation water measurement. Therefore, the flow measurement formula was then established. The relative error between the calculated and the actual flow was less than 5%, and the average relative error was 1.49%. The accuracy of flow measurement was higher than before. The excellent hydraulic performance was achieved in the flow-measuring flume of imitating long-eared owl wing. The finding can provide a strong reference to optimize the water resource allocation and fine-tuning water usage in irrigation areas.