The size and shape of small-scale current ripples: an experimental study using medium sand



Flume experiments with medium sand confirm the increasing complexity in the shape of small-scale current ripples with increasing flow velocity for constant depth. Experiments suggest that a measure of ripple shape (the ratio of wavelengths of transverse to streamwise features, λ-x/λ-z) has a more complex relationship with the flow property (Fr, H̄/d̄) (where Fr is Froude Number of the flow and H̄/d̄ is relative roughness), than was previously realized. It is suggested that hydraulic properties of the flow at the sediment water interface have a more general relationship with ripple form than do properties of the whole flow such as Froude and Reynolds Numbers. Properties of the whole flow tend to separate data into depthrelated curves at shallow flows where the free water surface influences the structure of the turbulence.