Verification of Three-dimensional Numerical Study of Scour in Channel, Sudden and Gradual Contractions using Experimental Data

This paper presents a verification of a numerical and experimental simulation of scour patterns at channel contractions using a 3-dimensional SSIIM (Sediment Simulation in Intakes with Multiblock option) model and laboratory tests. For this purpose, two states of sudden angle<not sign>-90 degrees and gradual angle-50 degrees contraction were simulated. The numerical model was calibrated and verified using the laboratory data. The accuracy of the model was calculated as 0.936 based on the Nash-Sutcliffe model efficiency coefficient, and 10.18% based on the mean relative error. Results showed that around 80%of scouring occurred during the first 20% of the equilibrium time. Also, it was concluded that the maximum rate of scouring occurred during the first hours of experiments and computations, and decreased with time. The results showed that the average scour rate for the sudden contraction state was 29.5% greater than the gradual state, which indicated a positive impact of gradualness of conversion in reducing maximum scour depth. This is an appropriate performance of the numerical model to simulate the scour pattern in channel contraction.