EXPERIMENTAL VERIFICATION OF SIMILARITY CRITERIA FOR EQUILIBRIUM BEACH PROFILES

Otavio S.F.J. Sayao, Jose Carlos Guimaraes

Abstract


This paper presents an attempt towards the determination of the geometric distortion for beach mobile bed models. At first, a derivation of a scaling law for modelling equilibrium beach profiles is given, based on Valembois' (1961) work. Further, an experimental verification of some criteria presented in literature for the reproduction of beach profiles in coastal mobile bed models (e.g. Noda, 1971; Yalin, 1971 and Vellinga, 1982) is carried out, leading to a comparison with the criterion developed herewith. Model experiments were undertaken in a two-dimensional wave flume with regular waves in an attempt to verify the validity of the four similarity criteria for the reproduction of beach profiles. For fine sand as model material, the experimental results proved valid the modified criterion based on Valembois (1961), among all criteria used. The use of this similarity criterion showed that the beach profiles were correctly reproduced in the model. The use of cellulose acetate as model material did not give good results, and none of the similarity criteria used were verified. The use of this lightweight material should be avoided for modelling beach processes. Further testing with finer sand is recommended to analyse the influence of the dimensionless fall time parameter (Dean, 1973) and to confirm its use for the prediction of equilibrium beach profiles.

Keywords


equilibrium beach profile; beach profile; similarity criteria; experimental verification

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