EXPERIMENTAL STUDY ON MODE REDUCTION PROCESS OF DOUBLE-ROW BARS

Abstract

Hydraulic experiments were conducted in order to clarify the mechanisms of mode reduction process of sand bars. Hydraulic conditions of these experiments were set large width-depth ratio. The following facts became clear by these experiments. Starting time of the mode reduction becomes late and time to spend on the mode reduction has the tendency which becomes long, when a width-depth ratio becomes large. One of two scoured area near side walls in double-row bars is buried and single-row bars are formed.
Furthermore, the prominence wave number of the bed form is analyzed. It is possible that the single row bars formed by mode reduction from double row bars are the same with the single row bars which are formed from the early stages of experiments on the bed form characteristics. Time changes of amplification of (α₂₁+α₄₀) and (α₁₁+α₂₀) have contributed greatly to the mode reduction process.