Experiments on suspension flow in open channels with bed forms

Abstract

The influence of bed forms in open-channel flow on the suspended sediment concentration distribution is experimentally studied. At one single measuring section the flow and the concentration profiles have been investigated in order to put the effect of bed forms into evidence. From these measurements the sediment- and momentum-diffusion coefficients, eq. 4, have been calculated; subsequently the |3-value, which appears in the Rouse relation, eq. 2, could be evaluated.

With these results it could be shown that the concentration distribution, given by the Rouse relation, is altered due to the presence of bed forms. The |3-value for suspension flow over bed form, being p > 1, appears to be larger than the one for comparable suspension flow over a plane bed, being f5 < 1. Also investigated is the evolution of the flow structure, measured along part of a bed form. The velocity distributions reveal a separating shear layer and a recirculating region. The turbulence and Reynolds-stress profiles show clear peaks in the vicinity of the shear layer.

Keywords:

• Open-channel flow. Suspension flow
• bed forms
• vertical concentration distribution
• turbulence