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Estimation of boundary shear stress distribution in open channels using flownet

Author(s): Guoliang Yu; Soon-Keat Tan

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Keywords: Flownet; potential flow; boundary shear stress; shear stress distribution; compound channel; energy dissipation

Abstract: An approach using flownet to calculate the boundary shear stress distribution along the wetted perimeter in a two dimensional flow is proposed. This approach is based on the assumption that the energy production balances the energy dissipation within the sub-area between two adjacent potential lines. The energy exchange induced by the large scale secondary flow cells between the sub-areas is neglected. The free water surface is used as the imaginary boundary to which the potential lines are perpendicular. The wetted cross section is mapped by orthogonal stream and potential lines. The wetted perimeter and cross section is divided into a number of segments and sub-area by the potential lines. The boundary shear stress over each boundary segment is the gravity force of the corresponding sub-area in the streamwise direction. The flownet method is applied to circular, rectangular, trapezoidal, and compound channels. The comparisons with experimental data and other analytical methods show that the flownet method estimates well the boundary shear stress distribution along the wetted perimeter, especially near the water margins and corners of the channel boundary where most of the existing analytical methods fail


Year: 2007

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