Bed Shear Stress in Unsteady Open-Channel Flows

by Iehisa Nezu, Kyoto Univ, Kyoto, Japan,
Hiroji Nakagawa, Kyoto Univ, Kyoto, Japan,
Yoshihiro Ishida, Kyoto Univ, Kyoto, Japan,
Akihiro Kadota, Kyoto Univ, Kyoto, Japan,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


In this study, velocity distributions over smooth and rough beds were accurately measured with an LDA in unsteady open-channel flows. The log-law distributions yielded well in the wall region for both the rising and falling stages of flood. The bed shear stress was evaluated reasonably from the log-law. These variations against the flood time coincided well with those evaluated from the momentum equation and also with the Reynolds stress measured directly. Of particular significance is the findings of counterclockwise loop of bed shear stress against the flow depth in unsteady flows.

Subject Headings: Shear stress | Flow measurement | Reynolds stress | River and stream beds | Shear flow | Open channels | Open channel flow | Unsteady flow

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