Laboratory Investigation on Changes in the Angles of the Invert Traps in Order to Increase the Trapping Efficiency

Abstract

Invert traps are one of the most effective methods for separating and collecting debris and dirt in order to remove them from residential areas for a cleaner environment. In the present study, experiments have been performed in 25 cm wide and 4 m long channel for 13 different invert trap configurations with 25 cm width and depth and 50 cm long with different input and output angles. To determine the best trap geometry that has the most retention ratios, four types of plastic beads as a laboratory sediments with the same density but different size and apparent weight, experiments were tested in a fixed time. Results showed that the input and output angles of the trap, has a considerable impact on the amount of deposited sediments. As, in the case of vertical walls of the entrance, whatever outlet wall of the trap has milder angle, trapping rate will be higher. In contrast, when the incoming angle of the trap has been smooth and the outlet wall is vertical, although sediments are easily sink in, but because of the strong vortices that formed downstream of the trap, much of this sediments re-suspension and directed away from the trap. Quantitative analysis of the results, showed that from the 13 tested geometries, trap with inlet angle of 90° and 34° as an outlet angle, has the highest efficiency on trapping the sediments.