Pattern selection and evolution for vortex ripples in sand
Abstract
Vortex ripples are a familiar occurrence in coastal waters, where the waves expose the sand surface at the sea bottom to an oscillatory flow. The name reflects the important role of the separation vortices that form on the lee side of the ripples in stabilizing the ripple slopes. In this talk recent laboratory experiments on vortex ripple formation in a one-dimensional annular geometry will be discussed, and a simple mass transfer model will be presented which captures some aspects of the wavelength selection and coarsening mechanisms. The key ingredient in the model is a transfer function, which describes the amount of mass eroded by a ripple from its downstream neighbor during one-half of the oscillation period. Using nonlinear data analysis, the transfer function can be determined from experimental runs, and the predictions of the mass transfer model can be compared to the experiment [1]. Theoretical issues of interest concern the determination of the selected wavelength from the shape of the transfer function [2] and the coarsening of the mean wavelength for transfer functions which are monotonically increasing [3]. [1] K.H. Andersen et al., Phys. Rev. Lett. 88, 234302 (2002). [2] J. Krug, Adv. Complex Systems 4, 353 (2001). [3] E.K.O. Hellén and J. Krug, Phys. Rev. E 66, 011304 (2002).
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2003
- Bibcode:
- 2003APS..MARA13008A