Impact of Flow in Pipe and Box Coverages on Open Channel’s Performance

Abstract

This experimental study aims to characterize the behavior of pipe and box coverages concerning their size, form, and upstream blockage ratio. In an artificial trapezoidal cross-section, five experimental cases were carried out: Case 1 involved an artificial canal without coverage or blockage; Cases 2 and 3 concerned pipe coverages with circular cross-sections (Pipe 1 and 2); Cases 4 and 5 involved box coverages with square cross-sections (Box 1 and 2). While the area of pipe 1 and box 1 are equal, the area of pipe 2 and box 2 is the same and greater than the area of pipe 1 and box 1. Three blockage ratios and three water flow rates were used in the experimental study. Each case included an investigation of the hydraulic performance of the open channel and the scouring pattern downstream of the coverage. In comparison to the case when there was no coverage present at the same condition, the presence of coverage in the open channel and the significant increase in flow rate, blocking ratio, and decreasing inlet area of coverage increased the heading up, head losses, scour depth, and scour length. In the same area and condition, the pipe coverage achieves greater scour depth and length than the box coverage. The box coverage is better for the open channels' performance than the pipe coverage. The research recommended using the box coverage rather than the pipe coverage and checking the maintenance processes to avoid the negative effect on the open channels' performance.

Keywords

• pipe coverage, box coverage
• open channel
• blockage ratio
• scour