n Values for Shallow Flow in Rough Channels

by F. J. Watts, Univ of Idaho, Moscow, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


Manning's friction factor n has been developed from flume data for very shallow open channel flow in a high-gradient channel with large bed material. n values are presented as a function of a relative roughness (the ratio of the standard deviation of roughness height derived from measured topography of the bed) divided by hydraulic radius, and Froude number. The bed surface was constructed of natural river rounded rock with sieve size ranging from 0.15 to 0.75 ft. The flow depth to D84 ratio ranged from 1.3/0.7 to 0.15/0.7 and therefore the flow was hyperturbulent (wake-interference). The material was stable for all runs. Two bed surface configurations were examined. Longitudinal slopes ranged from 0.008 to 0.018 and discharges ranged from 0.6 to 32.1 cfs.

Subject Headings: Open channel flow | Fluid flow | River flow | Hydraulic roughness | Bed materials | Friction | Water discharge

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