The effect of roughness strips on transverse mixing in hydraulic models

Turbulent transverse mixing is studied in an open channel flow in which the frictional resistance comes primarily from vertical metal strips. Analytically we obtain that the mixing coefficient ϵ = kau, where a is the strip width and u is the mean velocity. The analysis yields k = 0.08 as a minimum. An experiment in a laboratory flume verifies the form of the result and yields as an average k = 0.11.