Author(s): Ismail Aydin
Linked Author(s): Ismail Aydin
Keywords: Wall functions, bed roughness, channel flows, uniform flow, discharge
Abstract: Boundary roughness is an important hydraulic parameter in describing dynamics of free surface flows. There is no direct method to estimate the possible boundary resistance in natural environment. Available empirical formulations are based on the particle size on the river bed. However, other factors such as shape and size of flow section are also effective in the development of boundary resistance. Accurate prediction of boundary roughness can only be made by in situ hydraulic measurements for each specific flow domain. This paper use the experimental and computational approaches together to calculate the discharge and the boundary roughness. Flow is assumed to be uniform and velocity at the free surface is measured to be applied as boundary conditions of a numerical solution. Computational model uses a non-linear turbulence model that is capable of producing complete velocity field including turbulence driven secondary flows. Numerical solution requires repeated iterations for variable values of boundary roughness to adjust the velocity field to fit the measured values at the free surface. An explicit wall function is proposed for efficient calculation of the wall shear stresses and also for evaluation of the boundary roughness. The Method method is verified by a large number of data set obtained from a tilting flume in the laboratory
Year: 2017