TURBULENT STRUCTURE OF WATER AND CLAY SUSPENSIONS WITH BED LOAD

摘要

The discusser wishes to congratulate the authors for their excellent paper. He would like to discuss some possible drag reduction effects. The discusser has reanalyzed the authors' data assuming quasi-uniform flows at the end of the channel. For the clear-water flow experiments (runs C-1 and C-2), the data suggest an equivalent roughness height k_s of the flume (smooth plexiglass) between 0.15 mm and 0.19 mm. With these values, it is possible to compute the clear-water friction factors f for the clay-mud-flow experiments (M-1 and M-2), and to compare these values with the mudflow friction factor f_s. It is interesting to note that the clay-mud flow (runs M-1 and M-2) exhibits smaller flow resistance f_s than the clear-water flow: i.e. f_s/f < 1 (Fig. 18). Other researchers observed similarly some drag reduction caused by the presence of suspended sediments (Table 4). Fig. 18 presents model and prototype data of friction factor reduction as a function of the mean volumetric sediment concentration C_υ. Most data were obtained with suspended sediments without depositing material. The data of Buckley (1923) must be considered with great care as the changes in friction factor due to variation in bed configuration might be important.