The effect of tailwater depth on the dynamics of local scour

Abstract

The two-dimensional local scour occurring downstream from a submerged sluice gate for various tailwater depths was studied using a video imaging technique and a laser-Doppler anemometer. The flow field was found to be dynamic (i.e., varied with time). Previously reported equilibrium scour profiles for similar test conditions were not attained even after 96 h of laboratory testing. The scaling laws suggested in the literature were found to be unsuitable. New scaling laws are presented for the condition when a stable equilibrium state has not yet been attained. Velocity profiles are presented at various stations during digging and refilling conditions. Key words: local scour, time scale, video imaging, scour profile, velocity profile, sluice gate, cohesionless material, tailwater effect.