河床形態の変動特性に関する研究 ―その統計的構造について―

Abstract

In this paper, the authors study on the statistical structure of the configuration ofinoval bed in the range of Lower regime, F~.<l, and discribe the results of experimentsin the two channels which are different in width.The spectra of bed configuration along the longitudinal line, which are measured inspace and time, show interesting characteristics as follows. (1) The range of wave lengthof Alternating bar is about 2-10 times of width B, and the eminent wave length is 4.B.(2) The range of wave length of Dune spreads to about 10 times of depth Ii, and itsstatistical structure composes some "inertia subrange" in time and space, which has asimilarity independent of external conditions. The wave length of Dune accompanied withsurface water wave, which occurs when Fr. Is nealy 1, is about 4-5-h. (3) Another bedconfiguration is longitudinal streakings, the interval of which is 2.h lateraly. (4) Abovethree components are able to coincide each other according to hydraulic condition.In the latter half of this paper, the results of turbulence measured in the channelswith the fixed and moval bed are showed, and reveal that the occurrence and the growthof bed configuration has a close connection with the structure of turbulence.The experimental results indicate this statistical approach to phenomena of the inovalbed to be applicable even for the estimate of flow resistance.