Abstract
In open-channel turbulence with relatively large Reynolds number, water surface is subject to various types of fluctuations depending on the strength of turbulence. The level of fluctuation varies also with the Froude number and several researches have been conducted with respect to the root-mean-square value of surface oscillation. However, the mechanism that creates such water surface features has not been executed in detail in terms of turbulence vortex structure especially in rough-wall turbulence. This research aims at extracting a vortex structure that directly affects the water surface phenomenon by using an experimental technique with PIV and a sophisticated numerical technique with LES. A three-dimensional vortex structure that has an impact on surface features was successfully extracted from the LES results by using a conditional sampling technique.
