Laboratory study The effect of rack geometry on the efficiency of debris trapping and backwater

Accumulation of Debris in streams behind structures and bridge piers leads to the decrease of flow capacity, disruption of the discharge-scale relationship of control points and a negative impact on the performance and function of water structures. The use of rack structures is a common method of controlling debris. In this research, increasing the efficiency of the rack structure by redesigning this structure and also the amount of backwater behind this structure has been investigated. In these experiments, four types of rack geometry, three group of wood debris were investigated in the conditions of supercritical, critical and subcritical flow. Based on the results, the type of debris and flow conditions were ineffective in the efficiency of the rack and the best performance of the rack was the W-shaped rack with95% efficiency.However,the geometry of the rack and the flow conditions have affected the backwater in upstream, the v-shaped rack has created the lowest backwater with 0.14 %. except the geometry of the structure, the froude number of flow has affected the backwater.