Author(s): A. Gyr; A. Schmid

Linked Author(s):

Keywords:

Abstract: Experiments in an open channel were conducted to investigate the formation of ripples on an erodible sand bed by varying the roughness, the mass density of the uniform grain material and the history of the bed evolution. A first set ofexperiments was conducted by gradually increasing the slope in small increments from a value at which no transport occurred to one at which ripples started forming. In a supplementary set. the same slope change was achieved rapidly in a single step. Visualizations showed that two types of ripple formation exist, depending on how fast the slope rate was increased. A third type is observed for fine and heavy bed material (lead) at high bed load transport. The results can be interpreted by using a coherent structure model for the turbulent flow. In the framework of such a concept, the initial disturbances can be interpreted as transport relics of so-called sweep events, and the initial wave length is related to the sweep “periods”.

DOI: https://doi.org/10.1080/00221688909499244

Year: 1989