Eur. Phys. J. E 8, 465-476 (2002)
DOI: 10.1140/epje/i2001-10110-y
Long-time behavior of sand ripples induced by water shear flow
A. Betat1, C.A. Kruelle1, V. Frette1, 2 and I. Rehberg11 Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth, Germany
2 Department of Engineering, Stord/Haugesund College, Bjørnsonsgt. 45, N-5528 Haugesund, Norway
christof.kruelle@uni-bayreuth.de
(Received 9 March 2001 and Received in final form 2 July 2002 Online publication 8 October 2002)
Abstract
The formation of sand ripples under water shear flow
in a narrow annular channel and the approach of the ripple pattern
towards a steady state were studied experimentally. Four results are
obtained: i) The mean amplitude, the average drift velocity and the
mean sediment transport rate of the evolving bed shape are strongly
related. A quantitative characterization of this relation is given. ii) The
ripple pattern reaches a stationary state with a finite ripple amplitude
and wavelength. The time needed to reach the state depends on the
shear stress and may be several days. iii) The onset of ripple formation
is determined by the bed shear stress, but it seems neither to depend on
the grain diameter nor on the depth of the water layer. iv) The ripple
amplitude, drift velocity and sediment transport in this stationary state
depend on the grain size. This dependency is neither captured by the
particle Reynolds number nor by the Shields parameter: an empirical scaling
law is presented instead.
45.70.-n - Granular systems.
92.10.Wa - Sediment transport.
92.40.Gc - Erosion and sedimentation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002