ABSTRACT
In this study the local scour development around a single groin was investigated in the laboratory flume of the Norwegian University of Science and Technology (NTNU). The main goal of the experiments was to carry out a comprehensive data analysis on bed morphology, sediment transport, bed composition as well as hydrodynamics at conditions where bed armor development is expected. The length of the laboratory flume is 11 m, whereas the width is 1 m. The bed slope was set to 0.27%. The 0.33 m long groin was built 5 m far from the flume outlet. The experiment was carried out at three different constant discharges: https://www.w3.org/1998/Math/MathML"> Q 1 = 58 l / s , Q 2 = 72 l / s https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq9749.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> and https://www.w3.org/1998/Math/MathML"> Q 3 = 100 l / s https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq9750.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , respectively. Mixed size bed material with a d 50 of 5.16 mm was initially placed in the flume. The first experiment with the lowest discharge was run until reaching the equilibrium bed geometry. The second experiment started from this condition and was run until the new equilibrium condition, then the third experiment was carried out in the same way. During the experiments we continuously monitored the bed-load discharge, bed changes, water surface changes and 3D velocity measurements were also carried out. After each run the bed material composition was determined using an appropriate image analysis method. Based on the velocity measurements estimations could be obtained on local bed shear stress values. This feature was then related to the composition of the eroded sediment and the bed material. Such data analysis enhanced the selective erosion phenomenon which greatly contributes to the bed armor development. The well documented flume experiments are planned to serve as benchmark study for future numerical model development focusing on sediment transport investigations.
