Cross sectional flow in a meandering laboratory channel with vegetated bed

Abstract

As it is known, the outer-bank of a meander wave is considerably vulnerable to the erosion processes. Literature indicates that cross-stream circulation strongly affects the redistribution of the downstream velocity and boundary shear stress in curved channels. In steep outside bends, beside a central-region circulation cell, a counter-rotating circulation cell often forms in the upper part of the outer-bank region. Accurate understanding of the role of these circulation cells on velocity redistribution in bends is important to define protective measures of the outer-bank. Literature also shows that vegetation could modify flow velocity and turbulent structure. This work reports preliminary results of experimental work conducted in a large meandering channel with vegetation on the bed. The effect due the presence of vegetation on cross-stream flow and turbulence structure is examined by means of peculiar maps determined at the apex section in no-vegetatedbed and vegetated-bed conditions. The results have shown that, at the apex section, the presence of vegetation modifies the distribution of cross-sectional flow velocity and limits the action of the central-region circulation cell.