Experiments on a closed-conduit flow perturbed by a two- dimensional hill of low aspect ratio

Abstract eng:
We present here some preliminary results of an experimental study on the perturbation of a fully developed turbulent boundary layer by a two-dimensional hill of low aspect ratio. Water flows were imposed over an asymmetric hill, with a relatively small curvature, fixed on the bottom wall of a closed conduit. Particle image velocimetry (PIV) was used to measure the flow fields. For the flow upstream of the hill, we found some usual characteristics of a turbulent channel flow, such as logarithmic regions and typical profiles of the xy component of the Reynolds stress. Over the ripple, the maximum of the vertical component of the mean velocity is restrict to a narrow band, above the ripple surface, for every longitudinal position toward the crest. We also found the region where the Reynolds stress is perturbed, and the turbulent kinetic energy production was computed.

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