Accuracy of Numerical Simulation in Asymmetric Compound Channels

Abstract

In the recent years, compound channels received more attention in hydraulic engineering for their role in estimating and calculating the hydraulic parameters of natural rivers. Usually, for determination of the hydraulic parameters of compound channels, physical models are used which have cost and time assumption. According to the wide usage of numerical modeling in hydraulic engineering, this paper aims to evaluate the accuracy of numerical models in compound channels by simulating the hydraulic parameters in nine different types of compound channels and to compare them with experimental data. These simulations can show the interaction between velocity and vorticity and other hydraulic parameters by using contours and graphs along the channel length which help to have more and better understanding about their changes. Numerical simulations were performed using the renormalization-group turbulence model and volume-of-fluid free surface model for determining the level of fluid. Values of convergence ratio and the grid convergence index were calculated for evaluating the extrapolated values from numerical modeling and the sensitivity of the model solution to the numerical discretization, respectively, which indicates a proper validation of grid spacing and refinement selection for optimizing the calculation process. The comparison between numerical and experimental results shows a good agreement. The extracted numerical results show that by changing the floodplain width and depth, the water surface level changes 4–20% and 5–34%, respectively. Moreover, the numerical results show an increment of 20 and 145% in Froude and Weber numbers in floodplains, respectively, because of increment of velocity in floodplain.