Spatially-Averaged Stresses and Velocities Over Three-Dimensional Dunes (original) (raw)

2001

Abstract

In an effort to improve the understanding of the nature of flows over three-dimensional ripples and dune shapes on erodible beds, two complete sets of detailed flow measurements over fixed, artifical, sinuous-crested 3d dunes have been recently finished in the UCSB Ocean Engineering Laboratory's tilting-recirculating flume. Early results showed a relative increase in total boundary shear stress felt by the fluid due to the 3d dunes when compared with the 2d dunes for flows of the same mean depths and discharges. More detailed results from the completed 3d dune measurements are now presented and compared with the 2d dunes. In particular, both the turbulent kinetic energy and the Reynolds stresses over the 3d dunes are significantly lower than over the 2d dunes. To explain how an overall increase in total boundary shear stress could still result, estimates are made of the form drag from integrating the vertical component of the momentum equations, and of the skin friction from lo...

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