開水路粗度急変部における乱れ特性と浮遊砂濃度の遷移過程

Abstract

Before and behind bed protection works in natural rivers, bed roughnessabruptly changes from smooth to rough and/or rough to smooth. This paper dealswith water surface profiles and turbulent structures of open channel flows producedby sudden changes in bottom roughness experimentally and theoretically.Changes in vertical distribution of sediment concentration under the fullysuspended condition are also discussed. The transition of flow depth was found tobe mainly depend on the bed slope and classified into three types of flow patterns.In the downstream reach after roughness change, distributions of the velocity andturbulence property vary with development of the internal boundary layer, in whichthe transfer of turbulence energy by convection and vertical diffusion play dominantrole in the turbulence energy budget. The calculated results of the k-e andsediment transport models agree well with the experimental ones.