Ripple morphology under oscillatory flow: 1. Prediction

Abstract

Recent laboratory and field experiments have shown the inability of existing oscillatory flow ripple predictors to accurately predict both ripple size and ripple planform geometry. However, at this time, only partial adaptations of these predictors have been proposed to account for the observed discrepancies with new experimental data. The present work starts by presenting a comprehensive data set compiled from 27 literature studies and our own experimental data, which are presented in a companion paper. Dimensional analysis is used both to clarify the importance of the different variables involved in the development of ripples and to generate the basic dimensionless framework for the study of ripple morphology under oscillatory flow. Several ripple size and planform geometry predictors are contrasted against the compiled data set. Afterward, a new ripple wavelength and height predictor and a new planform geometry predictor are proposed, which overcome several of the limitations found in the earlier formulations. The new predictors emphasize the existence of local and global sediment transport mechanisms over a ripple bed, each of them acting at different scales. In particular, sediment size is found to have an important effect on the size and geometry of bed forms that can be generated by oscillatory flows.