Author(s): Yasuhiro Yoshikawa; Yasuharu Watanabe; Takaaki Abe; Akashi Ito
Linked Author(s):
Keywords: No Keywords
Abstract: In this study, field observations were conducted and observation data were analyzed to elucidate frazil particle distribution and frazil transport capacity. The distribution was statistically analyzed to clarify its characteristics, and the relationship between frazil transport capacity andflow strength was examined. The field observations were conducted on the Teshio River in Hokkaido, Japan. Frazil particle distribution was measured 189 times in total at five locations. At one of these points, frazil thickness was measured periodically five times in total. Flow velocity distribution was also determined by acoustic Doppler current profiler (ADCP). The observation data show the average frazil particle distribution. In fine frazil (0.2 to 1.0 mm diameter), the majority of particles were 0.4 to 0.6 mm in diameter, and the percentages of those measuring 0.2 to 0.4 mm or 0.6 to 1.0 mm were low. Among particles 1.0 mm or greater in diameter, the percentage of those measuring 1.0 to 2.0 mm was high, and it decreased with increase in particle size. There were more particles measuring 0.4 to 0.6 mm and 1.0 to 2.0 mm than those measuring larger or smaller, and the size distribution exhibited two peaks: one below 1 mm and the other above 1 mm. The analysis results of the observation data show a relational diagram for frazil transport capacity created using data from this study and using data on flow strength from a study by Shen (Shen, 1995). There are large variations in the observation data, probably because fixed values were given for frazil diameter/thickness and because time-series variations could not be expressed. The observation data in the present study are close to those of the previous study's relational expression, but the frazil transport capacity in the present study is higher, because the frazil diameter is small. This means that a greater amount of frazil with smaller particle diameters was transported in this study’s observation. The following things became clear by this research. The particle distribution showed two peaks: one below 1.0 mm, at 0.4 to 0.6 mm, and the other above 1.0 mm, at 1.0 mm to 2.0mm. Concerning the relationship between dimensionless frazil transport capacity and dimensionless flow strength, it was assumed that a large amount of frazil was transported in this study, as the particle diameter observed was smaller than that in a previous study.
Year: 2014