Abstract
The various coherent structures, such as kolk-boil vortices and the streaky structures, are often observed in the flood rivers and estuaries. The behavior of these structures is quite different between the rising and falling stages of the flood period. The unsteadiness effects of flood flows cause the these difference of turbulence. Therefore, it is important to investigate the turbulent structures in unsteady open-channel flows. In this study, the turbulent structures over smooth and rough beds were accurately measured by making use of LDA in unsteady open-channel flows. The unsteadiness effects upon the structures, mean velocity distribution, bed shear stress and turbulence characteristics and also the effect of secondary currents on them, were examined theoretically and experimentally.
