Study of the interactions between turbulent boundary layer and vegetated beds through an LDA system

This work is the first completion, as to the previous experimentations already issued, of the study of the interactions between an equilibrium boundary layer current flowing down a channel and the vegetated bottom surface. In particular, compared to the previous experimentations, the height of the cylinders employed to model the vegetation was increased, while their arrangement remained unchanged (that is according to rectangular or square meshes). The surveys of the local mean velocity distributions, carried out in subsequent sections of the flow by an LDA system, made it possible to point out that the increase in the height of the vegetation changes considerably the equilibrium state of the boundary layer, besides causing a further increase in the flow resistance and in the thickness of the boundary layer. With regard to this, the comparison with the previous experimentations made it possible both to define a parameter whose importance determines the passing from a “total” equilibrium state to a “partial” one and to point out the influence of the height of the cylinders either on the thickness of the boundary layer or on the local mean velocity distributions.