Author(s): C. Katopodis; H. K. Ghamry
Linked Author(s):
Keywords: Hydrodynamics; Rivers; Finite element; Numerical; Simulation; Velocity; Accuracy; Two dimensional
Abstract: The velocity field in natural rivers or channels is three dimensional and difficult to simulate numerically. Accurate model prediction of velocity fields benefit studies of complex flow phenomena such as those that occur in braided rivers, around islands, estuaries and river deltas, meandering rivers with wide floodplains, or flows of importance to ecology and aquatic habitats. In this context, successful computer modeling would be a useful prediction technique and a research tool to enhance our understanding of natural river dynamics. In this study the impact of varying mesh design construction and domain geometry on the accuracy of simulating velocity was investigated. Particular attention was paid to the sensitivity of each modeled river reach to the domain width, and the grid spacing. A wide range of node spacings were investigated, varying from 60 m down to 9 m, mesh nodes ranging from 1,666 up to 58,013 nodes, and domain widths ranging from 480 m to 800 m. Four study reaches of the Lower Athabasca River in northern Alberta, Canada, ranging in length from 6.3 km to 10.3 km, were simulated using the two-dimensional River2D finite element model (www. river2D. ca). Computed values for the average cross-sectional velocities were compared with river field surveys. The statistical mean absolute and root mean square error were used to evaluate the discrepancy between measured and predicted values. The results showed that significant accuracy in predicting the velocity field for the Lower Athabasca River could be attained through applying high resolution meshes within reasonable computational times. It is concluded that optimal values for the ratio of node spacing to reach width should be less than 0.029 to obtain the highest accuracy in simulating the average cross-sectional velocities.
Year: 2009