Bed Forms Generated on Sandy Bottom by Oblique Standing Waves

Abstract

This paper presents the results of a study of bed forms generated on a sandy bottom by an oblique standing wave resulting from obliquely incident long-crested waves on a fully reflecting vertical wall. Under antinodes of the oblique standing wave, the sand ripples have crests aligned perpendicular to the wall (type A); under nodes, the ripple crests are aligned with the wall and ride on the top of larger scale sandbars (type C), whereas “island” ripples of a honeycombed structure (type B) appear between nodes and antinodes of the oblique standing wave system. The type A and C ripples could be compared to those generated by long-crested progressive waves, whereas the sandbars at nodes, with ripples riding on them, were compared to those generated by two-dimensional standing waves. Results for the bed-form geometry of type A ripples, type C ripples, and sandbars, as well as type B “bottom islands,” are presented as a function of water particle semiexcursion, mobility number, and Shields parameter.