Laboratory investigation of hydraulic performance of silt screens

Abstract

Silt screen is a type of flexible barrier that has been widely deployed for the purpose of sediment containment in an aquatic environment. Yet, its working mechanism is still largely unknown. In this study, the authors presented the findings of an investigation of the hydraulic performance of silt screen using Particles Imaging Velocimetry (PIV) technique.The experiments were conducted in a 30 cm-wide flume, with a silt screen spanned across the whole width, normal to the flow. Three average flow velocities, U0 of 0.5 m/s, 0.1 m/s, and 0.2 m/s and different values of the penetration ratio (the ration between screen's penetration depth and flow depth) were simulated in the experiments. PIV images of the flow approaching the screen and that at the lee side of the silt screen were captured in the vertical mid-plane of the flume. The images were then processed, and analyzed to determine the velocity distribution, turbulence characteristics and streamlines patterns of the flow in the vicinity of the silt screen. Preliminary results showed that underflow through the gap between silt screen's lower end and the flume's bottom could be large. The experimental results also suggested a distinct change of flow patterns with the formation of recirculation areas at both sides of the screen. This paper attempts to elucidate the hydraulic performance of silt-screen in response to the magnitude of the environmental flow and different scenarios of screen configurations.