Author(s): Hajime Yamaguchi; Ken-Ichi Hirayama
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Keywords: No Keywords
Abstract: Through field measurements of ice regimes and velocity profiles for several years in Hokkaido, following results were obtained: (1) Ice conditions, which plays an important role in flow resistance, are classified into flat smooth ice cover, rippled ice cover and covers with frazil slush. At the ice degeneration period the wave form index of ice ripples may exceed a value of 0.1. (2) Performances of various current meters for measurements of flow under the cover were described. (3) From analysis of velocity profiles under the cover, it is concluded that average velocities for the upper ice regions are larger than velocities for the lower bottom region. (4) When the logarithmic velocity distribution is applied to the measured velocity profiles, calculated maximum velocities are slightly larger than measured velocities. However the adaptability of logarithmic distribution is generally satisfactory. (5) Majewski's method is used to obtain relative roughness height, friction factor and Manning's roughness coefficient of the ice cover, and the average values for flat smooth ice cover and ice cover with ripples were obtained as fi = 0.018,0. 053 and ni = 0.012,0. 021 respectively. (6) Relation between the relative depth of the maximum velocity and ratio of ni and nb shows a poor correlation, which indicates difficulties in determining the position of the maximum velocity. (7) Relation between wave form index of the ice ripples and friction coefficients was obtained.
Year: 1990