Impact of box section coverage on the hydraulic parameters of open channels

Abstract

Abstract The effects of box coverage blockage on the hydraulic characteristics of open channels within the case of sub-critical flow in the open channel were explored experimentally in research. Fifty-two test runs were utilized to attain the research's objectives, with four water discharges of 2, 5, 8, and 11 L/sec, three-box coverage side dimensions of 8.8, 10.4, and 12.90 cm, and four coverage blockage ratios of 0, 10, 20, and 30%. The water depth and velocity were measured in each run. The results revealed that increasing the blockage ratios, water discharge, and a diminishing within the area passing water through the coverage led to an increment of the heading up, head losses, and water surface level. The worst-case situation was a little coverage dimension (8.80 cm side) with 30% blockage and discharge of 11 L/s. Within blockage ratios, of 0, 10, 20, and 30% and discharge 11 L/s, the relative heading up ratio (hRu%) values were 85, 97, 111, and 125 percent respectively, and for the relative head losses ratio values downstream the coverages (hRloss%) were 88, 99, 113, and 131 percent respectively related to the depth of a non-coverage case. The flow velocities and the relative area passing water through the coverage were the most effective variables on heading up and head losses. The relative heading up and the relative head loss increased with the increment of the Froude number (Frd). Within a constant relative wetted area of coverage (Ar), and increasing the Froude number (Frd) by 0.01 percent, the relative heading up and relative head loss approximately increased by 5.5% and 6.2% respectively. It is recommended to implement the periodic maintenance of the coverage to improve the discharge capacity of the open channel.