Author(s): Shun-Ichiro Hayashi; Terunori Ohmoto
Linked Author(s):
Keywords: DNS; Open-channel turbulence; Coherent vortex structure; Dune-type wavy bed
Abstract: In this study, a fully-developed three-dimensional turbulent flow over a plural solid dune bed in an open-channel was reproduced by direct numerical simulation (DNS). Its coherent structures were also examined by using time-line technique and an identification of cylindrical vortex tubes. "Boil of the first kind", which was unique to the flow field on dune- type sand waves, was numerically reproduced. It was found that the kolk which causes the boil of the first kind can be detected as cylindrical vortex tubes rising from the bed. Findings also show that the boil of first kind and the kolk were generated not only from "hairpin vortices" as previously noted, but also from "reverse hairpin vortices" with their head near the bed and cyclonic vortices at their foot.
Year: 2005