Yoshio Muramoto

Bed Scour Profiles in Downstream Reaches of Various Types of Bed Protection Wroks

This paper reports characteristics of local scour formed in downstream reaches of various types of bed protection works. Four types of bed protection works are used in experiments under a dynamic equilibrium condition to investigate time related changes in scour profiles, maximum scour depths and locations. The scour processes are also discussed in comparison with bed shear stress distributions measured in the maximum scour hole.In addition, field observations of scour profiles were carried out at a downstream reach of hollow-squared blocks in the Manganji River in Hyogo Prefecture, and the observed scour profiles and velocity distributions were similar to those in the experiments.

Turbulent Structure of Open Channel Flows with Sudden Change in Bottom Roughness

Before and behind the bed protection works in natural rivers, the bed roughness abruptly changes from smooth to rough and rough to smooth. This paper deals with the water surface profile and turbulent structure of open channel flows with sudden change in bottom roughness experimentally and theoretically. Changes in vertical distribution of sediment concentration under the fully suspended condition are also discussed. The transition of flow depth was found to be mainly depend on the bed slope and classified into three types of flow patterns. In the downstream reach after roughness change, the velocity and turbulent Property distributions vary with development of the internal boundary layer, in w hich the transfer of turbulent energy by convection and vertical diffusion is dominant factor in the turbulent energy budget. The calculated results of the k-e and sediment transport models agree well with the experimental ones.