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 a longstanding and fascinating problem of hydraulics, motivating in the past few decades huge research on new models of turbulence. In this work, laboratory experiments are presented on a stream flowing on a heterogeneous pebble bed with varying slope. The analysis of the flow speed puts in evidence a clear inertial range, where the Kolmogorov 4/5-law for the streamwise velocity spatial increments holds. The law is used for a systematic estimation of the turbulent kinetic energy dissipation rate ϻ, here measured for three different bed slopes and hence for three different shear Reynolds numbers. The experiments presented here suggest that small scale turbulence has properties similar to the classical picture of homogeneous universal turbulence invoked by the Kolmogorov theory. [ABSTRACT FROM AUTHOR]