ABSTRACT
Antidunes are upper regime bedforms that may move upstream, downstream or remain stationary. Their most characteristic attribute is the approximate lack of phase shift between the bed and the undulating water surface. A hydraulic analysis has been carried out using the specific energy concept, treating a train of antidunes as a periodic succession of positive and negative steps. This reveals that stable antidunes could only exist under supercritical flow conditions, denying the existence of downstream migrating antidunes. Such an outcome disagrees with experimental evidence. We demonstrate that in order to explain the existence of downstream migrating antidunes with the specific energy principle, the non-hydrostatic pressure distribution in undular flows must be considered. Results of 2D numerical simulations over in-phase sinusoidal forms are presented to support the assumptions taken for the specific energy analysis, as well as experimental data for downstream migrating antidunes developed in a sand bed.
