Velocity Distributions around Blocked Trash Racks

Abstract

Transported debris in open channels can lead to accumulations and, therefore, cause blockages at trash racks. Velocity distributions and flow patterns change because of these blockages and may lead to geomorphic condition evolution around the blocked racks. Despite numerous investigations related to racks, systematic studies of velocity distributions around rack accumulations of debris blockage are missing. The debris accumulations were simulated using a horizontal plate blockage. The experiments were performed for different blockage ratios ($B_r=0.13$ , 0.25, 0.32, 0.45, 0.50, 0.64, and 0.69) and various approach Froude numbers (${\mathsf{F}}_o=0.06$ , 0.07, 0.08, 0.10, and 0.12) to analyze the up- and downstream velocity fields in the middle and near the wall in the flow direction around the rack. Overall, the results show that the velocity distributions were influenced by the blockage and new velocity results are provided for both up- and downstream of the rack. Additionally, a new average velocity equation is proposed for a rack with attached plate of large wood that considers the effects of blockage ratios and Froude numbers.