Author(s): Toshiki Ato; Tatsuhiko Uchida; Yoshihisa Kawahara
Linked Author(s): Tatsuhiko Uchida, Yoshihisa Kawahara
Keywords: No Keywords
Abstract: It is important for river management and maintenance to evaluate the drag force acting on river structures and vegetation. However, the characteristic of drag coefficient have not been revealed enough to be applied to nonuniform flows. In this work, a laboratory experiment was conducted in an open-channel with a uniform density of circular cylinders as a vegetation model. We measured depth profiles under various hydraulic conditions including uniform and non-uniform flows. The drag coefficient was obtained as a function of Froude number for the uniform flows. However, the function underestimated the drag force for the accelerated flow conditions. The additional term due to the pressure gradient around the vegetation to evaluate pressure reduction in the separation zone behind the cylinders was newly introduced for the accelerating flows and it was validated through the flow visualization and numerical calculations of the water depth profile.
Year: 2018