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Sand ripples under sea waves Part 2. Finite-amplitude development

Published online by Cambridge University Press:  26 April 2006

G. Vittori  and
P. Blondeaux
G. Vittori
Affiliation:
Istituto di Idraulica. Università di Genova, Via Montallagero, 1. 16145 Genova, Italy
P. Blondeaux
Affiliation:
Istituto di Idraulica. Università di Genova, Via Montallagero, 1. 16145 Genova, Italy
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Abstract

In the present paper we formulate a theory to predict the time development of sand ripples characterized by small but finite amplitude under the action of surface gravity waves. The theory is based on a weakly nonlinear stability analysis of a flat sandy bottom subject to viscous oscillatory flow. The parameters of the problem (namely the Reynolds number of the flow and the Reynolds and Froude numbers of sediments) are assumed to fall within a neighbourhood of the critical conditions determined in Blondeaux (1990). The analysis can predict the actual ripple height, wavelength and profile when flow separation is absent, i.e. for the case of rolling-grain ripples. Assuming Sleath's (1984) criterion for separation, the values of the relevant parameters at which transition from rolling-grain ripples to vortex ripples occurs are predicted. A comparison between theoretical findings and experimental data supports the validity of the present theory.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 218 , September 1990 , pp. 19 - 39
Copyright
© 1990 Cambridge University Press

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References

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