河川の大規模乱れ

Abstract

Observations of turbulent velocity are made in a river using a current meter. Thewidth of the river is 100 m and the depth is about 2 m. Moving average and powerspectrum analysis give the following results: (I) Maximum length of the large horizontaleddies in the river is about 10 times of the river width. (ii) Energy spectral density isdescribed by the well known "-5/3 power law ~', although the energy dissipation densityεtakes different values for the two zones, I.e. for the large horizontal turbulence ε=0. 03 cm2/sec3 and boundary layer turbulence 6 = 0. 2 crn2/sec3.