Turbulent energy dissipation rate in a tilting flume with a highly rough bed

Turbulent flows on highly rough beds, such as those occurring in natural watercourses, represent alongstanding and fascinating problem of hydraulics, motivating in the past few decades huge researchon new models of turbulence. In this work, laboratory experiments are presented on a stream flowingon a heterogeneous pebble bed with varying slope. The analysis of the flow speed puts in evidencea clear inertial range, where the Kolmogorov 4/5-law for the streamwise velocity spatial incrementsholds. The law is used for a systematic estimation of the turbulent kinetic energy dissipation rate ,here measured for three different bed slopes and hence for three different shear Reynolds numbers. Theexperiments presented here suggest that small scale turbulence has properties similar to the classicalpicture of homogeneous universal turbulence invoked by the Kolmogorov theory.