Comparison of flow and morphological characteristics in uniform and non-uniform sand bed channel

An experimental investigation has been carried out to evaluate the turbulent flow and morphological characteristics in an alluvial channel composed of uniform and non-uniform sand beds. The measures of turbulent flow parameters show that the streamwise mean velocity and Reynolds shear stress increase in the presence of the uniform sand bed, indicating a potential for a greater movement of sediment particles. The turbulent integral scale increases significantly with a uniform sand bed, which results in an increased energy and momentum transfer caused by the larger eddy size in the near bed region. Frequency analysis of the velocity time series was carried out with the help of the Hilbert-Huang transformation, which shows that the dominant time scale of the velocity time series data in a uniform sand bed channel is smaller as compared to the flow in a non-uniform sand bed channel.