Impact of one-side wart-type roughness on hydraulic resistance and flow dynamics in supercritical open-channel flows

The aim of this study is assess the impact on the Chezy roughness coefficient ( C c ), velocity distribution, energy dissipation and turbulent structures. The experiments were carried out in a rectangular flume at a bed slope of 2% that compared the smooth bed conditions with rough beds that had wart-like protrusions arranged at a 20 cm distance. Five transverse points (A-E) were measured to find the velocity profile, which were then analyzed using dimensionless parameters, power spectral density (PSD) and ANOVA (one-way). Findings have shown that one-sided wart-type roughness caused a very large decrease of Chezy coefficient by 9-27%, from 52.89-54.18 in smooth beds to 39.47-47.47. This decrease is an indication of significant rise in hydraulic resistance and turbulence. Heterogeneous velocity profiles were added by rough beds, and local velocities were 0.819-1.174 m/s versus the smooth bed of 1.151-1169 m/s. The dissipation of the energy was increased and the energy loss ( h L ) in rough channels was 0.0046 m almost twice of smooth channels (0.0027m). It was verified that rough beds have higher turbulence at higher wavenumbers by PSD analysis. The big effect of the roughness density on C c was verified by One-way ANOVA ( F = 48.14, p = 0.0001).