Avaliação hidráulica de escoamento livre com mudanças de direção com o auxílio de modelo experimental

Abstract

Surface water drainage structures are common in Brazil’s mining sector, often found in waste dumps, dams, pits, and other structures. The geometries of these structures can be influenced by various field conditions, such as earthwork constraints and/or available space. Sharp bends are commonly used to overcome these difficulties. This study explores open channel flow in sharp bends to identify the most efficient bend geometries from the flow depth increase and disturbance propagation perspective, contributing to improved hydraulic design in practical applications. An experimental model was constructed to study the phenomenon at the Centro de Pesquisas Hidráulicas (CPH) of the Universidade Federal de Minas Gerais (UFMG). The model consists of an acrylic channel with a width of 15 centimeters and a height of 35 centimeters, with bends at different angles (45º, 60º, and 90º) that, combined with the use of false channel beds to simulate steps and sills before and after each deflection, allow for various geometric configurations. Multiple angle records of the experiments were analyzed using a computational tool developed in Python programming language based on motion detection models to measure the flow depth, enabling the comparison of flow behavior across the different geometric configurations. Results show that both the channel bed geometry and the bend angle significantly impact flow behavior at sharp bends. In some cases, maximum depths observed at the bend reached up to five times the approach depths. Additionally, phenomena such as recirculation vortices, separation zones, and hydraulic jumps were identified in multiple tests. Regarding disturbance propagation, geometries B (step upstream and smooth bed downstream) and C (step upstream and sill downstream) exhibited the best performances upstream and downstream of the bend, respectively. Smoother deflection angles cause maximum depths further downstream, and disturbances propagate over longer distances. The results highlight the need for each practical scenario to be carefully evaluated before determining the most adequate geometry according to the desired design objectives.