Interaction between a rough bed and an adjacent smooth bed in open-channel flow

Experiments are conducted in an open-channel flow where half of the section is smooth and other consists array cubes, which either submerged or emergent. A shear layer featuring large-scale Kelvin–Helmholtz structures develops between two subsections. The flows first analysed framework double-averaging method (averaging both time space). Double averaging could be performed thanks to experimental set-up (three-dimensional, two-component telecentric scanning particle image velocimetry) that allows measure velocity field a large volume, including interstices cubes. momentum balance on subsection indicates loss towards rough has same order magnitude than through bed friction. This lateral flux occurs nearly exclusively turbulent stress, whereas secondary currents plays minor role dispersive stress negligible. pattern recognition technique then applied investigate statistically develop layer. appear coherent over water depth strongly inclined vertical, top part being ahead. educed structure responsible by itself for shape profile across turbulence (up 60 % stress). Finally, coupling identified passage instantaneous wake around cubes at interface.