Resistance to Flows in Alluvial Channels

by ChiEmeka G. Ilo, Principal Agricultural Engineer; Soil and Water Resources, East Central State, Nigeria; on leave as Commonwealth Research Scholar, Indian Inst. of Tech., Bombay, India,

Serial Information: Journal of the Hydraulics Division, 1975, Vol. 101, Issue 6, Pg. 665-679

Document Type: Journal Paper


A direct method of predicting flow resistance and uniform velocity in alluvial channels is developed. The method covers all known bed-form regimes and not only eliminates trial-and-error computations and use of rigid-boundary channel flow formulas but also avoids the difficulties associated with the use of the various existing alluvial channel flow computation techniques. The study shows that the Darcy-Weisbach friction factor can be expressed as a unique function of the ratio of the bed form and grain shear stress components for any anticipated discharge and flow geometry, the bed-form shear component being uniquely determinable from the flow and channel material characteristics. The results confirm that the friction factor is nonconstant but varies with the bed-form regime. The applicability of the method to laboratory flumes, field canals, and natural rivers is illustrated.

Subject Headings: Channel flow | Alluvial channels | Bed forms | Shear stress | Load and resistance factor design | Flow resistance | Computing in civil engineering | Friction

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