TURBULENCE CHARACTERISTICS IN ROUGH UNIFORM OPEN-CHANNEL FLOW

Laboratory experiments on the turbulence structure of rough, uniform open-channel flow are reported, The particular aim was to investigate reasonably large relative roughnesses, k(s)/D approximate to 0.1, as can be encountered in gravel streams, Velocity profiles and turbulence intensity as well as Reynolds-stress profiles were measured, It was found that: (i) the universal law of the wall (with Br approximate to 8.5) explains the inner region data well; in the outer region, the law of the wake (with II = 0.09) is observed; (ii) the distributions of the turbulence intensity and the Reynolds stress (Figs 4 and 5) show a diminishing tendency as the free surface is approached; (iii) the mixing length (Fig. 6) increases over the how depth; (iv) the energy spectra (Fig, 7) display well the inertial sub-range characteristics; the different turbulent scales, L(x), lambda and eta, fall in decades apart.