Manning’s Coefficient

In this experimental study the Manning’s roughness coefficient, n, is investigated in steady-uniform-turbulent water flows, within sloped (Jo) rectangular open channels of artificial very large (and equal) walls ’ roughness elements. The channel’s bed is always smooth, but both walls’ roughness elements are varying, through adhesive vertical rubber strips (κxh, where, κ=4mm and h=8 mm), the last dimension being perpendicular to the walls. Any strip is at various equal distances λ (at any experimental Series) from the next strip, and thus the research is interested in the determination of the relationships among n, Re, λ/h=50-25-12.5, and for h=0 λ/h=∞. A number of Figs. are presented concerning n and n/ns (ns=roughness coefficient for almost smooth channel) vs Re and λ/h ratios, and some interpretations are given for the pertinent curves. The present study is aiming at helping the hydraulic engineer in his practical water flow problems